SaralPhysics is a platform or approach designed to make the study of physics easy, clear, and enjoyable. It explains complex concepts, formulas, and laws in simple language with the help of real-life examples, illustrations, and step-by-step explanations. The main goal is to help students understand physics deeply, solve problems effectively, and apply concepts in practical situations.
Assertion (A): When a body is charged, its mass changes.
Reason (R): Charge is quantized.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Jab body charge hoti hai (positive ya negative), to usme se electrons ya to nikalte hain ya add hote hain. Kyunki electrons ka mass hota hai, isliye body ka total mass change ho jaata hai. Reason (R) bhi sahi hai ki charge quantized hota hai (e ke multiple mein), lekin ye Assertion (A) ka direct reason nahi hai. Mass change hone ka reason electron ka transfer hai.
Question 2:
Assertion (A): Electric field lines do not form closed loops.
Reason (R): Electric field is conservative in nature.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Electric field lines positive charge se shuru hokar negative charge par khatam ho jaati hain, ye kabhi closed loop nahi banati. Aisa isliye hota hai kyunki electric field conservative nature ka hota hai. Iska matlab hai ki ek charge ko closed path mein ghumane par total work done zero hota hai, jo tabhi possible hai jab field lines closed loop na banayein.
Question 3:
Assertion (A): A metallic shield in the form of a hollow shell may be built to block an electric field.
Reason (R): In a hollow spherical shield, the electric field inside it is zero at every point.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Kisi bhi hollow metallic conductor (shell) ke andar electric field hamesha zero hota hai. Is phenomenon ko electrostatic shielding kehte hain. Isliye, hum sensitive instruments ko external electric field se bachane ke liye metallic shield ka use kar sakte hain. Reason (R) bilkul sahi tarah se Assertion (A) ko explain kar raha hai.
Question 4:
Assertion (A): On going away from a point charge, the electric field decreases.
Reason (R): The electric field is inversely proportional to the square of the distance from the point charge.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Point charge ki vajah se electric field ka formula E = kq/r² hota hai. Is formula se saaf hai ki electric field (E) distance (r) ke square ke inversely proportional hai. Iska matlab jaise-jaise distance badhega, electric field ki value kam hoti jayegi.
Question 5:
Assertion (A): The net force on an electric dipole in a uniform electric field is zero.
Reason (R): The forces on the two charges of the dipole are equal and opposite.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Uniform electric field mein, dipole ke positive charge (+q) par force (qE) field ki direction mein lagta hai aur negative charge (-q) par utna hi force (qE) field ki opposite direction mein lagta hai. Kyunki dono forces equal aur opposite hain, wo ek dusre ko cancel kar dete hain, isliye net force zero ho jaata hai.
Question 6:
Assertion (A): The electric field at the surface of a conductor is always perpendicular to the surface.
Reason (R): If the field were not perpendicular, a component of the field would exist along the surface, causing charges to move.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Ek conductor ke surface par, electric field hamesha surface ke perpendicular (90 degree par) hota hai. Agar aisa na ho aur field ka koi component surface ke along (parallel) ho, to wo component conductor ke free electrons par force lagayega aur wo move karne lagenge, jisse surface current ban jayega. Lekin electrostatic condition mein koi current nahi hota, isliye field perpendicular hi hona chahiye.
Question 7:
Assertion (A): Gauss's law is true for any closed surface, no matter what its shape or size.
Reason (R): The term q in Gauss's law includes the sum of all charges enclosed by the surface.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Gauss's law kisi bhi shape ya size ke closed surface ke liye valid hai, isliye Assertion (A) sahi hai. Reason (R) bhi sahi hai ki Gauss's law mein 'q' ka matlab surface ke andar band (enclosed) sabhi charges ka total sum hota hai. Lekin, Reason (R) ye explain nahi karta ki law har shape ke liye kyu valid hai. Law ke har shape ke liye valid hone ka reason inverse square law ka nature hai.
Question 8:
Assertion (A): A soap bubble expands on being charged.
Reason (R): Due to the repulsion between like charges, an outward force acts on the surface of the bubble.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Jab aap ek soap bubble ko charge karte hain, to wo charge uski poori surface par fail jaata hai. Kyunki saare charges same nature ke (ya to positive ya negative) hote hain, wo ek dusre ko repel (pratikarshit) karte hain. Is repulsion ki vajah se surface par bahar ki taraf ek pressure lagta hai, jisse bubble ka size badh jaata hai yaani wo expand ho jaata hai.
Question 9:
Assertion (A): The work done in moving a charge on an equipotential surface is zero.
Reason (R): The potential difference between any two points on an equipotential surface is zero.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Equipotential surface ka matlab hai ek aisi surface jiske har point par potential same hota hai. Work done ka formula W = q(V₂ - V₁) hota hai. Kyunki equipotential surface par V₁ = V₂, isliye potential difference (V₂ - V₁) zero ho jaata hai. Is vajah se, charge ko is surface par move karne mein kiya gaya work done bhi zero hota hai.
Question 10:
Assertion (A): Two electric field lines can never cross each other.
Reason (R): If they cross, there would be two directions of the electric field at the point of intersection, which is impossible.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Electric field lines kabhi ek dusre ko kaat (intersect) nahi sakti. Aisa isliye hai kyunki kisi bhi point par electric field line ki tangent us point par electric field ki direction batati hai. Agar do lines ek point par kaatengi, to us point par field ki do alag-alag directions ho jayengi, jo physical roop se possible nahi hai.
Chapter 2: Electrostatic Potential and Capacitance
Question 1:
Assertion (A): For a charged particle moving from point P to point Q, the net work done by an electrostatic field on the particle is independent of the path connecting P to Q.
Reason (R): The net work done by a conservative force on an object moving along a closed loop is zero.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Assertion sahi hai kyunki electrostatic field ek conservative field hai. Reason bhi sahi hai, ye conservative force ki property hai. Lekin Reason, Assertion ka direct explanation nahi hai. Assertion ka correct reason ye hai ki 'electrostatic field conservative hai'.
Question 2:
Assertion (A): The potential of a conductor is the same throughout its volume and on its surface.
Reason (R): In the case of a conductor, the electric field is zero inside it.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Conductor ke andar Electric Field (E) zero hota hai. Relation E = -dV/dr se, agar E=0 hai to V ko constant hona padega. Isliye potential poore conductor mein (volume and surface) same rehta hai.
Question 3:
Assertion (A): When a dielectric slab is inserted between the plates of a capacitor (kept connected to a battery), the potential difference between the plates remains the same.
Reason (R): The capacitor is connected to the battery, so the voltage is maintained.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Jab tak capacitor battery se connected rehta hai, uske plates ke beech ka potential difference battery ke voltage ke barabar rehta hai. Isliye dielectric daalne par bhi potential difference change nahi hoga.
Question 4:
Assertion (A): If the distance between parallel plates of a capacitor is halved, its capacitance is doubled.
Reason (R): The capacitance of a capacitor is inversely proportional to the distance between the plates.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Parallel plate capacitor ka formula C = ε₀A/d hota hai. Isse saaf hai ki capacitance (C) distance (d) ke inversely proportional hai. Isliye jab aap distance ko half (d/2) karenge to capacitance double (2C) ho jayegi.
Question 5:
Assertion (A): Two adjacent conductors carrying the same positive charge have no potential difference between them.
Reason (R): The potential of a conductor depends only on its charge.
Correct Answer: (d) A is false and R is also false.
Explanation: Assertion galat hai. Do alag conductors ka potential unke shape, size aur aas-paas ke doosre conductors par bhi depend karta hai. Isliye same charge hone par bhi potential alag ho sakta hai. Reason bhi galat hai, potential sirf charge par nahi, balki shape, size aur medium par bhi depend karta hai.
Question 6:
Assertion (A): Electric field is always normal to the equipotential surfaces.
Reason (R): If the electric field were not normal, it would have a component along the surface, which would cause work to be done in moving a charge on the surface.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Equipotential surface par charge move karne mein work done zero hota hai. Ye tabhi possible hai jab force (electric field) displacement ke perpendicular ho. Agar field normal nahi hoga, to uska ek component surface ke along hoga jo charge ko move karwayega aur work done hoga, jo equipotential ki definition ke khilaf hai.
Question 7:
Assertion (A): The capacitance of a parallel plate capacitor increases when a dielectric slab is introduced.
Reason (R): The dielectric constant of the medium is always greater than 1.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Jab dielectric slab daalte hain, to capacitance K times badh jaati hai (C_new = K * C_original). Kyunki sabhi dielectric materials ke liye dielectric constant (K) 1 se bada hota hai, isliye capacitance hamesha badhti hai.
Question 8:
Assertion (A): If three capacitors of capacitance C1 < C2 < C3 are connected in parallel, then their equivalent capacitance C_p > C3.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Parallel combination mein equivalent capacitance sabhi individual capacitances ka sum hoti hai. Isliye, jo total value aayegi wo hamesha sabse badi individual capacitance (C3) se bhi badi hogi.
Question 9:
Assertion (A): When charges are shared between two bodies, there is usually a loss of energy.
Reason (R): The potential of both bodies becomes equal after sharing.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Jab do alag-alag potential waale conductors ko connect karte hain, to charge flow hota hai aur connecting wire mein heat ke form mein energy ka loss hota hai. Isliye Assertion sahi hai. Charge tab tak flow hota hai jab tak dono ka potential same na ho jaaye, isliye Reason bhi sahi hai. Lekin Reason, Assertion ka correct explanation nahi hai. Energy loss ka reason charge flow ke dauraan heat generation hai.
Question 10:
Assertion (A): A single isolated conductor can have capacitance.
Reason (R): The capacitance of a single conductor is defined with the other conductor assumed to be at infinity.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Ek single conductor bhi charge store kar sakta hai. Uski capacitance ko define karne ke liye hum maante hain ki doosri plate/conductor infinity par hai, jiska potential zero hota hai. Is concept se, ek isolated spherical conductor ki capacitance 4πε₀R aati hai.
Chapter 3: Current Electricity
Question 1:
Assertion (A): Drift velocity of electrons is very small though current in a conductor may be large.
Reason (R): The number density of free electrons in a metal is very large.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Current \( I = nqAv_d \). Metals में \(n\) बहुत बड़ा होता है, इसलिए \(v_d\) बहुत छोटा होने पर भी \(I\) बड़ा हो सकता है—यही Assertion का कारण है।
Question 2:
Assertion (A): Ohm’s law is a fundamental law of physics.
Reason (R): It is valid for all materials and at all temperatures.
Correct Answer: (d) A is false and R is also false.
Explanation: Ohm’s law एक empirical relation है (fundamental नहीं) और केवल ohmic conductors/कुछ स्थितियों पर ही लागू होता है; सभी materials/temperatures पर नहीं।
Question 3:
Assertion (A): The internal resistance of a cell decreases with increase in temperature.
Reason (R): Rise in temperature increases ionic mobility in the electrolyte.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Temperature बढ़ने पर ions की mobility बढ़ती है, जिससे electrolyte की effective resistivity घटती है और internal resistance कम होता है।
Question 4:
Assertion (A): Kirchhoff’s junction rule is based on conservation of charge.
Reason (R): Charge cannot accumulate at a junction in steady state.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Steady state में किसी junction पर incoming और outgoing currents का sum बराबर होता है क्योंकि net charge जमा नहीं हो सकता—यही charge conservation है।
Question 5:
Assertion (A): A voltmeter is always connected in parallel across a component.
Reason (R): A voltmeter has a very high resistance.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Parallel connection से वही potential difference मापा जाता है और high resistance होने से circuit से बहुत कम current खींचता है, जिससे reading disturb नहीं होती।
Question 6:
Assertion (A): When resistors are connected in series, the same current flows through each resistor.
Reason (R): In series combination, the potential difference across each resistor is the same.
Correct Answer: (c) A is true but R is false.
Explanation: Series में current same रहता है पर potential differences resistances के proportional होते हैं, equal नहीं।
Question 7:
Assertion (A): A galvanometer can be converted into an ammeter by connecting a low resistance (shunt) in parallel with it.
Reason (R): The shunt provides a low-resistance path so that most of the current bypasses the galvanometer.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Shunt parallel लगाने से भारी current shunt में जाता है और galvanometer सुरक्षित रहते हुए total current को मापा जा सकता है।
Question 8:
Assertion (A): The equivalent resistance of two resistors in parallel is always less than the smaller of the two resistances.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Reciprocal relation से \(R_p\) हमेशा smallest resistance से भी कम आता है।
Question 9:
Assertion (A): The emf of a cell is greater than its terminal potential difference when current is drawn from it.
Reason (R): A part of the emf is spent across the internal resistance of the cell.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Load के समय \(V = E - Ir\). Internal resistance \(r\) पर potential drop \(Ir\) होने से terminal voltage \(E\) से कम हो जाता है।
Question 10:
Assertion (A): Current in a conductor flows due to the drift of free electrons under an electric field.
Reason (R): The drift velocity of electrons is directly proportional to the applied electric field.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Current का कारण electrons का drift है; proportionality \(v_d \propto E\) material property (mobility) बताती है, पर current के होने का direct कारण नहीं समझाती—इसलिए (b)।
Chapter 4: Moving Charges and Magnetism
Question 1:
Assertion (A): A moving electric charge produces a magnetic field around it.
Reason (R): Stationary charges also produce a magnetic field.
Correct Answer: (c) A is true but R is false.
Explanation: Moving charges ही magnetic field बनाते हैं, जबकि stationary charges केवल electric field बनाते हैं।
Question 2:
Assertion (A): The direction of magnetic field around a straight current-carrying conductor is given by the right-hand thumb rule.
Reason (R): If thumb points along current, then curled fingers show field direction in concentric circles around the wire.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Right-hand thumb rule से ही हम conductor के चारों तरफ के circular field की direction पाते हैं।
Question 3:
Assertion (A): The magnetic field inside a long solenoid is nearly uniform.
Reason (R): Magnetic field lines inside a solenoid are parallel and equally spaced.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Field lines parallel और equally spaced होने से field uniform हो जाता है।
Question 4:
Assertion (A): At the center of a circular current-carrying loop, the magnetic field is maximum.
Reason (R): The field contributions due to current elements add in the same direction at the center.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Circular loop के center पर हर element की magnetic field एक ही दिशा में add होती है, इसलिए maximum होती है।
Question 5:
Assertion (A): Force on a moving charge in a magnetic field is maximum when velocity is perpendicular to the field.
Reason (R): Magnetic force is given by \( F = qvB \sin \theta \).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: जब θ = 90°, sinθ = 1 ⇒ force maximum होता है।
Question 6:
Assertion (A): A charge moving parallel to the magnetic field experiences no force.
Reason (R): Magnetic force depends on \( \sin \theta \) between velocity and field, and sin0° = 0.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Parallel motion में θ = 0 ⇒ force zero होता है।
Question 7:
Assertion (A): A charged particle moving perpendicular to a uniform magnetic field follows a circular path.
Reason (R): The magnetic force provides the necessary centripetal force for circular motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Magnetic force हमेशा perpendicular होता है, जिससे वो centripetal force की तरह act करता है।
Question 8:
Assertion (A): A current-carrying conductor placed in a magnetic field experiences a force.
Reason (R): Force per unit length is given by \( F = IBL \sin \theta \).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: यह Fleming’s left-hand rule से भी explain किया जाता है।
Question 9:
Assertion (A): In a velocity selector, both electric and magnetic fields are used.
Reason (R): For a specific velocity, electric and magnetic forces cancel each other.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: जब \( qE = qvB \), तभी particle बिना deflect हुए निकलता है।
Question 10:
Assertion (A): Magnetic force does no work on a charged particle.
Reason (R): The force is always perpendicular to the displacement of the particle.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Work \( = \vec{F} \cdot \vec{d} = Fd\cos \theta \). यहां θ = 90°, इसलिए work = 0।
Chapter 5: Magnetism and Matter
Question 1:
Assertion (A): A freely suspended bar magnet always comes to rest in North–South direction.
Reason (R): Earth itself behaves like a huge bar magnet.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Earth ke andar molten iron aur current-like motions hote hain jisse ek global magnetic field banta hai. Isi field ki wajah se freely suspended magnet apne north–south axis ke along align ho jata hai — isliye R, A ko sahi se explain karta hai.
Question 2:
Assertion (A): Magnetic monopoles exist in nature.
Reason (R): A magnet can be divided into smaller pieces and still retains its poles.
Correct Answer: (c) A is false but R is true.
Explanation: Jab aap bar magnet ko todte ho to har tukde mein dono poles (north aur south) rehte hain — isliye magnet ko todne se koi isolated single pole (monopole) nahi milta. Is wajah se Assertion galat hai. Reason bilkul sahi hai kyunki har chhote piece ka bhi dono poles hote hain.
Question 3:
Assertion (A): The magnetic moment of a current loop increases if the current is increased.
Reason (R): Magnetic moment μ = I × A (for a single loop, area A).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Magnetic moment μ current (I) aur loop ke area (A) ka product hota hai. Agar I badhaya jaye to μ proportional badhega. Isliye Reason directly Assertion ko justify karta hai.
Question 4:
Assertion (A): A soft iron piece is used to make electromagnets.
Reason (R): Soft iron has high retentivity.
Correct Answer: (c) A is true but R is false.
Explanation: Soft iron ko electromagnet banane ke liye use kiya jaata hai kyunki uski permeability bahut high hoti hai — matlab woh easily magnetise ho jata hai aur field ko badha deta hai. Lekin soft iron ki retentivity low hoti hai (wo demagnetise ho jata hai jab current band ho), isliye Reason galat hai.
Question 5:
Assertion (A): Magnetic susceptibility of diamagnetic substances is negative.
Reason (R): Diamagnetic substances are repelled by a magnetic field.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Diamagnetic materials me induced magnetisation external field ke opposite direction me hoti hai, isliye unki susceptibility χ negative hoti hai. Ye bhi sach hai ki ye materials weakly magnetic field se repel karte hain — dono statements consistent hain aur reason assertion ko samjhata hai.
Question 6:
Assertion (A): Earth’s magnetic field is due to motion of charges in its core.
Reason (R): Rotating molten iron currents in the core act like a dynamo.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Geodynamo theory ke mutabik, Earth ke core me moving conductive fluid (molten iron) se currents generate hote hain, jo magnetic field banate hain. Isliye Reason Earth ke magnetic field ka sahi explanation deta hai.
Question 7:
Assertion (A): Magnetic field lines form closed continuous loops.
Reason (R): Isolated north or south magnetic poles exist.
Correct Answer: (c) A is true but R is false.
Explanation: Magnetic field lines kabhi break nahi karte aur hamesha closed loops banate hain, isliye Assertion sahi hai. Lekin isolated magnetic monopoles ab tak practical experiments me nahi mile — isliye Reason galat hai.
Question 8:
Assertion (A): Permanent magnets are commonly made of steel.
Reason (R): Steel has high coercivity.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Permanent magnets banane ke liye aise materials chahiye jinki coercivity high ho taki woh magnetisation ko retain kar saken; steel (aur kuch alloys) ki coercivity comparatively high hoti hai, isliye steel ka use permanent magnets me hota hai — Reason assertion ko support karta hai.
Question 9:
Assertion (A): Gauss’s law in magnetism states that net magnetic flux through any closed surface is zero.
Reason (R): Magnetic monopoles do not exist.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Gauss’s law for magnetism (∮B·dA = 0) ka matlab hai net flux zero — kyunki field lines closed loops me hote hain aur unka koi start/end isolated pole par nahi hota. Reason (monopoles ka non-existence) is law ka direct reason hai.
Question 10:
Assertion (A): Magnetic declination is the angle between the magnetic meridian and the geographic meridian at a place.
Reason (R): At all places on Earth, magnetic meridian and geographic meridian always coincide.
Correct Answer: (c) A is true but R is false.
Explanation: Magnetic declination wahi angle batata hai jahan compass (magnetic meridian) true north (geographic meridian) se tilt karta hai. Reason galat hai kyunki dono meridians aksar coincide nahi karte; isliye declination non-zero hota hai kai jagahon par.
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Chapter 6: Electromagnetic Induction
Question 1:
Assertion (A): Whenever magnetic flux linked with a coil changes, an emf is induced in it.
Reason (R): This is in accordance with Faraday’s law of electromagnetic induction.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Faraday ne bataya tha ki induced emf ka magnitude flux ke rate of change par depend karta hai. Isliye flux change hone par emf appear hota hai — reason assertion ko justify karta hai.
Question 2:
Assertion (A): The minus sign in Faraday’s law (ε = -dΦ/dt) is due to Lenz’s law.
Reason (R): Induced emf hamesha usi change ko oppose karta hai jiske wajah se wo produce hua.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Minus sign ka matlab hai opposition. Lenz’s law kehta hai ki nature hamesha oppose karega flux change ko — isi wajah se minus sign Faraday’s law me aata hai.
Question 3:
Assertion (A): Self-induction is called the inertia of electricity.
Reason (R): It opposes any change in current flowing through the coil.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Jaise mass inertia oppose karta hai motion ke change ko, waise hi self-induction oppose karta hai current ke change ko. Isi wajah se ise electrical inertia bhi bolte hain.
Question 4:
Assertion (A): Mutual induction takes place between two coils placed close to each other.
Reason (R): Changing current in one coil changes magnetic flux linked with the second coil.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Primary coil me current badalne par uske around flux change hota hai jo secondary coil se link ho jata hai — isse secondary coil me emf induce hota hai.
Question 5:
Assertion (A): Induced emf is always produced when a conductor moves parallel to magnetic field.
Reason (R): Fleming’s right-hand rule explains the direction of induced emf.
Correct Answer: (c) A is false but R is true.
Explanation: Conductor ko emf tabhi milega jab wo field ko cut kare (perpendicular component ho). Agar motion field ke parallel hai to flux change hi nahi hoga, emf zero hoga. Reason sahi hai kyunki direction find karne ke liye Fleming ka rule use hota hai.
Question 6:
Assertion (A): Eddy currents are undesirable in most cases.
Reason (R): They produce heating and energy losses in the conductor.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Large metal pieces me eddy currents unwanted heating aur wastage karte hain, isliye appliances me laminated cores use hote hain. Reason bilkul correct hai.
Question 7:
Assertion (A): A transformer cannot work on direct current (DC).
Reason (R): Transformer works on the principle of mutual induction which requires changing magnetic flux.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: DC me flux constant rehta hai isliye mutual induction possible nahi. AC hi flux ko change karta hai aur transformer ko kaam karata hai.
Question 8:
Assertion (A): Induction furnace is based on eddy current heating.
Reason (R): Rapidly changing magnetic field produces large circulating currents inside the metal.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Alternating magnetic field me metal ke andar heavy eddy currents generate hote hain jo resistive heating ke through furnace ko garam karte hain.
Question 9:
Assertion (A): In a generator, mechanical energy is converted into electrical energy.
Reason (R): Generator works on the principle of electromagnetic induction.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Coil ko mechanically rotate karne se flux change hota hai aur emf induce hota hai — isi se generator electrical output deta hai.
Question 10:
Assertion (A): Induced emf can be increased by using a coil of many turns.
Reason (R): Induced emf is directly proportional to the rate of change of flux linkage (NΦ).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Agar ek coil me N turns hain to emf = -N dΦ/dt hota hai. Zyada turns ka matlab zyada emf — reason assertion ko clearly explain karta hai.
Chapter 7: Alternating Current
Question 1:
Assertion (A): In an AC circuit, the current and voltage are always in phase for a pure resistor.
Reason (R): A pure resistor does not store energy but dissipates it as heat.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Pure resistor mein voltage aur current ke beech koi phase difference nahi hota kyunki resistor energy store nahi karta, balki usse heat ke roop mein dissipate karta hai.
Question 2:
Assertion (A): The power factor of a purely inductive circuit is zero.
Reason (R): In a purely inductive circuit, the current lags the voltage by 90 degrees.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Purely inductive circuit mein current voltage se 90° peeche hota hai, isliye power factor (cos φ) zero hota hai kyunki cos 90° = 0.
Question 3:
Assertion (A): A capacitor in an AC circuit offers low impedance to high-frequency signals.
Reason (R): Capacitive reactance is inversely proportional to frequency.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Capacitive reactance Xc = 1/(2πfC) hoti hai, jo frequency ke inversely proportional hai. High frequency par Xc kam hota hai, isliye impedance bhi kam hota hai.
Question 4:
Assertion (A): An inductor in an AC circuit opposes rapid changes in current.
Reason (R): Inductive reactance is directly proportional to frequency.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Inductive reactance XL = 2πfL hoti hai, jo frequency ke saath badhti hai. Isliye inductor current ke rapid changes ko oppose karta hai.
Question 5:
Assertion (A): The average power in an AC circuit is zero for a purely inductive or capacitive circuit.
Reason (R): In purely inductive or capacitive circuits, the phase difference between voltage and current is 90 degrees.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Average power P = Vrms Irms cos φ hoti hai. Purely inductive ya capacitive circuit mein φ = 90°, isliye cos 90° = 0 aur power zero hoti hai.
Question 6:
Assertion (A): An LCR series circuit can exhibit resonance.
Reason (R): At resonance, the inductive reactance equals the capacitive reactance.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Resonance tab hota hai jab XL = Xc, jisse impedance minimum hota hai aur current maximum hota hai. Yeh LCR series circuit ka property hai.
Question 7:
Assertion (A): A choke coil is used to reduce current in an AC circuit without significant power loss.
Reason (R): A choke coil has high inductance and low resistance.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Choke coil ka high inductance current ko limit karta hai bina significant power loss ke, kyunki uska resistance kam hota hai.
Question 8:
Assertion (A): The RMS value of an AC is equivalent to the DC value that produces the same heating effect.
Reason (R): RMS value is defined as the square root of the mean of the squares of instantaneous values of current or voltage.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: RMS value (Irms = √(I²avg)) wahi heating effect deta hai jo equivalent DC deta hai, aur yeh definition ke hisaab se mean square ka root hota hai.
Question 9:
Assertion (A): The impedance of an LCR circuit is minimum at resonance.
Reason (R): At resonance, the net reactance of the circuit becomes zero.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Resonance par XL = Xc, isliye net reactance (XL - Xc) zero ho jata hai, aur impedance Z = √(R² + (XL - Xc)²) minimum (equal to R) hota hai.
Question 10:
Assertion (A): In an AC circuit, a capacitor allows high-frequency signals to pass easily.
Reason (R): The reactance of a capacitor decreases with increasing frequency.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Capacitor ka reactance Xc = 1/(2πfC) frequency ke saath kam hota hai, isliye high-frequency signals asani se pass ho jate hain.
Chapter 8: Electromagnetic Waves
Question 1:
Assertion (A): Electromagnetic waves are transverse in nature.
Reason (R): Electric and magnetic fields in electromagnetic waves oscillate perpendicular to each other and to the direction of wave propagation.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Electromagnetic waves mein electric aur magnetic fields ek doosre ke aur wave ke direction ke perpendicular oscillate karte hain, isliye yeh transverse waves hote hain.
Question 2:
Assertion (A): Electromagnetic waves do not require a medium to propagate.
Reason (R): They are produced by oscillating electric and magnetic fields.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: EM waves oscillating electric aur magnetic fields se bante hain, jo vacuum mein bhi propagate kar sakte hain, isliye medium ki zarurat nahi hoti.
Question 3:
Assertion (A): The speed of electromagnetic waves in vacuum is equal to the speed of light.
Reason (R): Speed of EM waves in vacuum is given by c = 1/√(μ₀ε₀).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: EM waves ki speed vacuum mein c = 3×10⁸ m/s hoti hai, jo formula c = 1/√(μ₀ε₀) se milti hai, jahan μ₀ aur ε₀ constants hain.
Question 4:
Assertion (A): Radio waves are a type of electromagnetic wave.
Reason (R): Radio waves have the longest wavelength in the electromagnetic spectrum.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Radio waves EM spectrum ka part hain aur unki wavelength sabse lambi hoti hai (10³ m tak), jo unhe EM waves ka ek type banata hai.
Question 5:
Assertion (A): X-rays can penetrate soft tissues but are stopped by bones.
Reason (R): X-rays have high frequency and high penetrating power.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: X-rays ki high frequency unhe high energy aur penetrating power deti hai, isliye wo soft tissues se pass ho jate hain lekin dense bones se ruk jate hain.
Question 6:
Assertion (A): Microwaves are used in radar communication.
Reason (R): Microwaves have short wavelengths and can be easily focused into beams.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Microwaves ki wavelength chhoti hoti hai (1 mm se 1 m), jo unhe focused beams banane ke liye suitable banati hai, isliye radar mein use hote hain.
Question 7:
Assertion (A): Ultraviolet rays can cause skin damage.
Reason (R): UV rays have high energy due to their high frequency.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: UV rays ki high frequency unhe high energy deti hai, jo skin cells ko damage kar sakti hai, jaise sunburn ya skin cancer ka risk.
Question 8:
Assertion (A): Gamma rays are the most penetrating electromagnetic waves.
Reason (R): Gamma rays have the highest frequency in the electromagnetic spectrum.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Gamma rays ki frequency sabse zyada hoti hai, jo unhe highest energy aur penetrating power deta hai, isliye wo matter ke through asani se pass ho jate hain.
Question 9:
Assertion (A): Infrared waves are used in remote controls.
Reason (R): Infrared waves have wavelengths longer than visible light but shorter than microwaves.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Infrared waves ki wavelength visible light se lambi aur microwaves se chhoti hoti hai, jo unhe remote controls ke liye suitable banati hai.
Question 10:
Assertion (A): Electromagnetic waves carry energy and momentum.
Reason (R): EM waves exert radiation pressure when they strike a surface.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: EM waves energy aur momentum carry karte hain, aur jab wo kisi surface par strike karte hain to radiation pressure exert karte hain, jo unke momentum ka proof hai.
Chapter 9: Ray Optics and Optical Instruments
Question 1:
Assertion (A): The angle of deviation by a prism is minimum when the angle of incidence equals the angle of emergence.
Reason (R): At minimum deviation, the refracted ray inside the prism is parallel to the base of the prism.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Minimum deviation tab hoti hai jab angle of incidence aur angle of emergence barabar hote hain, aur is condition mein prism ke andar refracted ray prism ke base ke parallel hoti hai.
Question 2:
Assertion (A): A convex lens can form a virtual and magnified image.
Reason (R): When an object is placed between the focus and the optical centre of a convex lens, the image formed is virtual and magnified.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Jab object convex lens ke focus aur optical centre ke beech rakha jata hai, to image virtual, erect aur magnified banta hai, jo assertion ko explain karta hai.
Question 3:
Assertion (A): A concave mirror can form a real and inverted image.
Reason (R): When an object is placed beyond the centre of curvature of a concave mirror, the image formed is real and inverted.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Concave mirror jab object ko centre of curvature ke bahar rakha jata hai, to real aur inverted image banta hai, jo assertion ka sahi explanation hai.
Question 4:
Assertion (A): Total internal reflection occurs when light travels from a denser to a rarer medium.
Reason (R): The angle of incidence must be greater than the critical angle for total internal reflection to occur.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Total internal reflection tab hoti hai jab light denser medium se rarer medium mein jati hai aur angle of incidence critical angle se bada hota hai.
Question 5:
Assertion (A): A convex mirror always forms a virtual and diminished image.
Reason (R): The image formed by a convex mirror is always located behind the mirror, irrespective of the object’s position.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Convex mirror hamesha virtual aur diminished image banata hai jo mirror ke peeche form hota hai, object ki position se nahi badalta.
Question 6:
Assertion (A): The power of a lens is measured in dioptres.
Reason (R): Power of a lens is defined as the reciprocal of its focal length in metres.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Lens ki power dioptre mein measure ki jati hai aur yeh focal length (metres mein) ka reciprocal hoti hai, i.e., P = 1/f.
Question 7:
Assertion (A): A microscope uses a convex lens to produce a highly magnified image.
Reason (R): The objective lens of a microscope forms a real, inverted, and magnified image, which is further magnified by the eyepiece.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Microscope ka objective lens real, inverted aur magnified image banata hai, jise eyepiece aur magnify karta hai, isliye total magnification high hoti hai.
Question 8:
Assertion (A): A telescope is used to observe distant objects by making them appear closer.
Reason (R): The objective lens of a telescope forms a real image of a distant object, which is magnified by the eyepiece.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Telescope ka objective lens distant object ka real image banata hai, jise eyepiece magnify karta hai, isse object nazdeek dikhayi deta hai.
Question 9:
Assertion (A): The critical angle for a medium depends on its refractive index.
Reason (R): The critical angle is given by sin⁻¹(1/μ), where μ is the refractive index of the denser medium.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Critical angle denser medium ke refractive index par depend karta hai aur iska formula sin⁻¹(1/μ) hai, jo assertion ko explain karta hai.
Question 10:
Assertion (A): A convex lens can behave as a diverging lens when placed in a medium of higher refractive index.
Reason (R): The nature of a lens depends on the relative refractive indices of the lens material and the surrounding medium.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Agar convex lens ko usse zyada refractive index wale medium mein rakha jaye, to woh diverging lens ki tarah behave karta hai, kyunki lens ka behaviour relative refractive index par depend karta hai.
Chapter 10: Wave Optics
Question 1:
Assertion (A): In Young’s double-slit experiment, interference fringes are formed due to the superposition of light waves.
Reason (R): The two slits act as coherent sources of light, producing waves that interfere constructively and destructively.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Young’s double-slit experiment mein do slits se nikalne wali light waves coherent hoti hain, jo constructive aur destructive interference karti hain, jisse fringes bante hain.
Question 2:
Assertion (A): The distance between consecutive bright fringes in Young’s experiment increases with increasing wavelength.
Reason (R): Fringe width is directly proportional to the wavelength of light used.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Fringe width β = λD/d hoti hai, jahan λ wavelength hai. Zyada wavelength se fringe width badhti hai, jo assertion ko explain karta hai.
Question 3:
Assertion (A): Diffraction of light occurs when it passes through a narrow slit.
Reason (R): Diffraction is the bending of light around the edges of an obstacle or aperture.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Diffraction light ke edges ya narrow slit se guzarne par bending ke wajah se hoti hai, jo wave nature ka pramaan hai aur assertion ko explain karta hai.
Question 4:
Assertion (A): Polarisation of light proves that light is a transverse wave.
Reason (R): Only transverse waves can be polarised, as their oscillations occur perpendicular to the direction of propagation.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Polarisation sirf transverse waves mein possible hai kyunki unki oscillations propagation ke perpendicular hoti hain, jo light ke transverse nature ko prove karta hai.
Question 5:
Assertion (A): In a single-slit diffraction experiment, the central maximum is wider than other maxima.
Reason (R): The central maximum is formed due to constructive interference of all wavelets from the slit.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Single-slit diffraction mein central maximum sabhi wavelets ke constructive interference se banta hai, isliye yeh doosre maxima se zyada wide hota hai.
Question 6:
Assertion (A): The resolving power of a microscope increases with decreasing wavelength of light.
Reason (R): Resolving power is inversely proportional to the wavelength of light used.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Resolving power ∝ 1/λ hoti hai, isliye chhoti wavelength (jaise UV light) se microscope ka resolving power badhta hai.
Question 7:
Assertion (A): In Young’s double-slit experiment, if one slit is covered, interference fringes disappear.
Reason (R): Interference requires two coherent sources of light.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Interference ke liye do coherent sources chahiye. Ek slit cover karne par sirf ek source bachta hai, isliye fringes nahi bante.
Question 8:
Assertion (A): Huygens’ principle can explain both interference and diffraction of light.
Reason (R): Huygens’ principle states that every point on a wavefront acts as a source of secondary wavelets.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Huygens’ principle ke according wavefront ke har point se secondary wavelets nikalte hain, jo interference aur diffraction patterns ko explain karte hain.
Question 9:
Assertion (A): The intensity of light in the dark fringes of an interference pattern is zero.
Reason (R): Dark fringes are formed due to destructive interference where the resultant amplitude is zero.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Dark fringes destructive interference ke wajah se bante hain, jahan do waves ka resultant amplitude zero hota hai, isliye intensity bhi zero hoti hai.
Question 10:
Assertion (A): The resolving power of a telescope increases with the diameter of its objective lens.
Reason (R): Resolving power is directly proportional to the diameter of the objective lens and inversely proportional to the wavelength of light.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Telescope ka resolving power ∝ D/λ hota hai, jahan D objective lens ka diameter hai. Bada diameter aur chhoti wavelength resolving power ko badhate hain.
Chapter 11: Dual Nature of Radiation and Matter
Question 1:
Assertion (A): Photoelectric effect demonstrates the particle nature of light.
Reason (R): Light consists of photons, which transfer energy to electrons, causing their emission from a metal surface.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Photoelectric effect mein light photons ke roop mein energy transfer karta hai, jo electrons ko metal se nikal deta hai, yeh light ki particle nature ko darshata hai.
Question 2:
Assertion (A): The threshold frequency is the minimum frequency required to eject electrons from a metal surface.
Reason (R): Electrons are ejected only when the energy of incident photons exceeds the work function of the metal.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Threshold frequency woh minimum frequency hai jisme photon ki energy metal ke work function se zyada hoti hai, tabhi electrons emit hote hain.
Question 3:
Assertion (A): The kinetic energy of photoelectrons increases with increasing frequency of incident light.
Reason (R): The energy of a photon is directly proportional to its frequency (E = hν).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Photon ki energy E = hν frequency ke saath badhti hai. Zyada frequency se photon ki energy bhi zyada hoti hai, jo photoelectrons ke kinetic energy ko badhata hai.
Question 4:
Assertion (A): The stopping potential in the photoelectric effect is independent of the intensity of light.
Reason (R): Stopping potential depends on the maximum kinetic energy of photoelectrons, which is determined by the frequency of light.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Stopping potential photoelectrons ke maximum kinetic energy par depend karta hai, jo light ki frequency se aata hai, na ki intensity se.
Question 5:
Assertion (A): Matter waves are associated with moving particles like electrons.
Reason (R): De Broglie hypothesis states that a particle with momentum p has a wavelength λ = h/p.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: De Broglie ke according, kisi bhi moving particle (jaise electron) ke saath ek wave judi hoti hai, jiska wavelength λ = h/p hota hai.
Question 6:
Assertion (A): The de Broglie wavelength of a particle decreases as its mass increases.
Reason (R): De Broglie wavelength is inversely proportional to the momentum of the particle.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: De Broglie wavelength λ = h/p hota hai. Agar mass badhta hai, to same velocity ke liye momentum (p = mv) badhta hai, jisse wavelength kam hota hai.
Question 7:
Assertion (A): Electron diffraction confirms the wave nature of electrons.
Reason (R): Electrons produce interference patterns when passed through a double slit, similar to light waves.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Electron diffraction mein electrons double slit se guzarne par interference pattern banate hain, jo unki wave nature ko confirm karta hai.
Question 8:
Assertion (A): The photoelectric effect cannot be explained by the wave theory of light.
Reason (R): Wave theory cannot account for the instantaneous emission of electrons or the threshold frequency.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Wave theory ke according energy continuously spread hoti hai, jo instantaneous emission aur threshold frequency ko explain nahi kar sakti, isliye particle theory zaroori hai.
Question 9:
Assertion (A): The number of photoelectrons emitted is proportional to the intensity of incident light.
Reason (R): Intensity of light is proportional to the number of photons striking the surface per unit time.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Light ki intensity photon ke number par depend karti hai. Zyada intensity ka matlab zyada photons, jo zyada photoelectrons emit karte hain.
Question 10:
Assertion (A): The de Broglie wavelength of a macroscopic object is negligible.
Reason (R): For macroscopic objects, the momentum is very large, making the wavelength extremely small.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Macroscopic objects ka mass bada hota hai, jisse unka momentum (p = mv) bhi bada hota hai. Isliye λ = h/p bahut chhota hota hai, jo negligible hai.
Chapter 12: Atoms
Question 1:
Assertion (A): In Rutherford’s scattering experiment, most alpha particles passed through the gold foil without deflection.
Reason (R): The atom consists mostly of empty space, with a small, dense nucleus at its center.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Rutherford ke experiment mein alpha particles ka seedha guzar jana is baat ka pramaan hai ki atom ka zyadatar hissa khali hota hai aur nucleus chhota aur dense hota hai.
Question 2:
Assertion (A): The Bohr model successfully explains the line spectrum of hydrogen.
Reason (R): Electrons in the hydrogen atom can occupy only certain quantized energy levels.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Bohr model ke according, electrons sirf quantized energy levels mein rehte hain, aur jab yeh levels ke beech transition karte hain, to specific wavelengths ka light emit hota hai, jo hydrogen ka line spectrum banata hai.
Question 3:
Assertion (A): The radius of the electron’s orbit in the Bohr model is quantized.
Reason (R): The angular momentum of the electron in Bohr’s model is given by mvr = nħ, where n is an integer.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Bohr model mein electron ka angular momentum quantized hota hai (mvr = nħ), jisse orbit ka radius bhi quantized hota hai, jo assertion ko explain karta hai.
Question 4:
Assertion (A): The energy of an electron in a hydrogen atom is negative.
Reason (R): The negative energy indicates that the electron is bound to the nucleus.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Hydrogen atom mein electron ka energy negative hota hai kyunki woh nucleus ke attraction se bound hota hai, aur yeh binding energy negative sign se represent hoti hai.
Question 5:
Assertion (A): The frequency of emitted radiation in the hydrogen atom depends on the energy difference between two orbits.
Reason (R): According to Bohr, the energy of emitted photon is given by hν = ΔE, where ΔE is the energy difference between two energy levels.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Bohr model ke according, jab electron higher se lower orbit mein jata hai, to emitted photon ki frequency hν = ΔE se di jati hai, jahan ΔE do energy levels ka difference hai.
Question 6:
Assertion (A): Rutherford’s model could not explain the stability of an atom.
Reason (R): According to classical electromagnetic theory, an accelerating electron should continuously emit radiation and lose energy.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Rutherford model mein electron nucleus ke around orbit mein chakkar lagata hai, jo classical theory ke according energy lose karke nucleus mein gir jana chahiye, lekin aisa nahi hota, isliye model atom ki stability explain nahi karta.
Question 7:
Assertion (A): The spectral lines of hydrogen are grouped into series like Lyman, Balmer, and Paschen.
Reason (R): Each series corresponds to electron transitions ending at a specific energy level.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Hydrogen ke spectral lines different series mein hote hain (jaise Lyman n=1, Balmer n=2), kyunki electron specific energy levels par transition karta hai.
Question 8:
Assertion (A): The ionization energy of a hydrogen atom is 13.6 eV.
Reason (R): Ionization energy is the energy required to remove an electron from the ground state (n=1) to infinity.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Hydrogen atom ke ground state (n=1) se electron ko infinity tak le jane ke liye 13.6 eV energy chahiye, jo ionization energy hai.
Question 9:
Assertion (A): The energy levels of a hydrogen atom are inversely proportional to the square of the principal quantum number.
Reason (R): The energy of an electron in the nth orbit is given by Eₙ = -13.6/n² eV.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Bohr model ke according, hydrogen atom ke energy levels Eₙ = -13.6/n² eV se di jati hain, jo principal quantum number (n) ke square ke inversely proportional hote hain.
Question 10:
Assertion (A): The Balmer series lies in the visible region of the electromagnetic spectrum.
Reason (R): The Balmer series corresponds to electron transitions from higher energy levels to the n=2 energy level.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Balmer series mein electron higher levels se n=2 par aata hai, jisse emitted photons ki wavelength visible region (400-700 nm) mein hoti hai.
Chapter 13: Nuclei
Question 1:
Assertion (A): The mass of a nucleus is less than the sum of the masses of its constituent nucleons.
Reason (R): The mass defect is converted into binding energy, which holds the nucleus together.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Nucleus ka mass uske nucleons ke individual masses ke sum se kam hota hai kyunki mass defect binding energy (E = Δmc²) mein convert hota hai, jo nucleus ko bind rakhta hai.
Question 2:
Assertion (A): The binding energy per nucleon is higher for stable nuclei.
Reason (R): Higher binding energy per nucleon indicates greater stability of the nucleus.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Zyada binding energy per nucleon ka matlab hai ki nucleus zyada tightly bound hai, jo uski stability ko darshata hai.
Question 3:
Assertion (A): Alpha particles are helium nuclei.
Reason (R): An alpha particle consists of two protons and two neutrons.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Alpha particle ek helium nucleus (₂He⁴) hai, jisme do protons aur do neutrons hote hain, jo assertion ko explain karta hai.
Question 4:
Assertion (A): Beta decay increases the atomic number of the nucleus by one.
Reason (R): In beta-minus decay, a neutron transforms into a proton, emitting an electron and an antineutrino.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Beta-minus decay mein neutron proton mein badal jata hai, jisse atomic number ek se badh jata hai aur ek electron aur antineutrino emit hota hai.
Question 5:
Assertion (A): Gamma rays are emitted during nuclear de-excitation.
Reason (R): Gamma rays are high-energy photons released when a nucleus transitions from a higher to a lower energy state.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Gamma rays high-energy photons hote hain jo nucleus ke higher energy state se lower state mein jane par emit hote hain, jo nuclear de-excitation ka process hai.
Question 6:
Assertion (A): Nuclear fission releases a large amount of energy.
Reason (R): In fission, a heavy nucleus splits into two lighter nuclei, converting some mass into energy.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Nuclear fission mein heavy nucleus do lighter nuclei mein toot jata hai, jisme mass defect energy (E = Δmc²) ke roop mein release hoti hai.
Question 7:
Assertion (A): Nuclear fusion occurs in the core of stars like the Sun.
Reason (R): Fusion involves the combination of light nuclei to form a heavier nucleus, releasing energy.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Stars ke core mein high temperature aur pressure par light nuclei (jaise hydrogen) combine hokar heavier nucleus (jaise helium) banate hain, jisse energy release hoti hai.
Question 8:
Assertion (A): The half-life of a radioactive substance is constant.
Reason (R): Half-life is the time taken for half of the radioactive nuclei in a sample to decay, independent of the initial amount.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Half-life ek radioactive substance ki intrinsic property hai jo initial amount se independent hoti hai aur decay rate par depend karti hai.
Question 9:
Assertion (A): The size of a nucleus is proportional to its mass number.
Reason (R): The radius of a nucleus is given by R = R₀A^(1/3), where A is the mass number.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Nucleus ka size mass number (A) ke saath badhta hai, aur iska radius R = R₀A^(1/3) se diya jata hai, jahan R₀ ek constant hai.
Question 10:
Assertion (A): Radioactivity is a spontaneous process.
Reason (R): Radioactive decay occurs without any external influence and follows statistical laws.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Radioactivity ek spontaneous process hai jo external factors se affected nahi hota aur statistical probability ke according hota hai.
Chapter 14: Semiconductor Electronics: Materials, Devices and Simple Circuits
Question 1:
Assertion (A): Semiconductors have a partially filled valence band and a partially empty conduction band at room temperature.
Reason (R): The energy gap between the valence band and conduction band in semiconductors is small, allowing thermal excitation of electrons.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Semiconductors mein chhota band gap (1-2 eV) hota hai, jisse room temperature par electrons valence band se conduction band mein thermally excite ho sakte hain, isliye valence band partially filled aur conduction band partially empty hota hai.
Question 2:
Assertion (A): Doping increases the conductivity of a semiconductor.
Reason (R): Doping introduces additional charge carriers in the semiconductor material.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Doping se n-type ya p-type impurities add ki jati hain, jo extra electrons ya holes (charge carriers) provide karti hain, jisse semiconductor ki conductivity badhti hai.
Question 3:
Assertion (A): A p-n junction diode allows current to flow easily in one direction but not in the opposite direction.
Reason (R): In forward bias, the potential barrier at the p-n junction is reduced, allowing current flow.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: P-n junction diode forward bias mein potential barrier kam karta hai, jisse current asani se flow karta hai, lekin reverse bias mein barrier badhta hai, jisse current nahi guzarta.
Question 4:
Assertion (A): A Zener diode is used as a voltage regulator.
Reason (R): Zener diode maintains a constant output voltage in reverse bias near its breakdown voltage.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Zener diode reverse bias mein breakdown voltage ke paas constant voltage maintain karta hai, isliye iska use voltage regulator ke roop mein hota hai.
Question 5:
Assertion (A): An n-type semiconductor has electrons as the majority charge carriers.
Reason (R): N-type semiconductors are formed by doping with pentavalent impurities, which provide extra electrons.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: N-type semiconductor mein pentavalent impurities (jaise phosphorus) dope kiye jate hain, jo extra electrons dete hain, jisse electrons majority charge carriers ban jate hain.
Question 6:
Assertion (A): A p-type semiconductor has holes as the majority charge carriers.
Reason (R): P-type semiconductors are formed by doping with trivalent impurities, which create electron vacancies called holes.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: P-type semiconductor mein trivalent impurities (jaise boron) dope kiye jate hain, jo electron vacancies (holes) create karte hain, jisse holes majority charge carriers ban jate hain.
Question 7:
Assertion (A): A transistor can be used as an amplifier.
Reason (R): A small change in the base current of a transistor causes a large change in the collector current.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Transistor mein base current mein chhota change collector current mein bada change lata hai, jo signal amplification ke liye use hota hai.
Question 8:
Assertion (A): A light-emitting diode (LED) emits light when forward-biased.
Reason (R): In forward bias, recombination of electrons and holes in an LED releases energy in the form of photons.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: LED mein forward bias par electrons aur holes recombine hote hain, jisse energy photon ke roop mein release hoti hai, jo light produce karti hai.
Question 9:
Assertion (A): The resistance of an intrinsic semiconductor decreases with increasing temperature.
Reason (R): At higher temperatures, more electrons are thermally excited from the valence band to the conduction band.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Intrinsic semiconductor mein temperature badhne par zyada electrons valence band se conduction band mein excite hote hain, jisse charge carriers badhte hain aur resistance kam hota hai.
Question 10:
Assertion (A): A rectifier converts alternating current (AC) to direct current (DC).
Reason (R): A diode in a rectifier circuit allows current to flow in one direction only, effectively converting AC to pulsating DC.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Rectifier circuit mein diode AC ko ek direction mein flow karne deta hai, jisse pulsating DC milta hai, jo AC ko DC mein convert karta hai.
Class 11 Physics - Assertion Reason Questions (English Medium)
Class 11 Physics: Assertion & Reason Questions (Complete Syllabus)
Namaste Students! Welcome to Premium Physics Hub. Yahan aapko Class 11 Physics ke har chapter ke 10 Assertion-Reason questions milenge, specially CBSE/NCERT syllabus ke according. Har question ke saath detailed Hinglish explanation hai taaki aap easily samajh sakein. Practice karein aur exams mein top karein! Let's get started!
Instructions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option out of the choices given below.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is NOT the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.
Chapter 1: Physical World
Question 1:
Assertion (A): Physics is considered a fundamental science.
Reason (R): Physics deals with the basic laws governing the universe.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Physics ko fundamental science maana jata hai kyunki yeh universe ke basic laws jaise motion, energy, aur matter ke interactions ko study karta hai. Reason (R) yeh sahi tarah se explain karta hai ki physics basic laws par based hai, jo assertion ko justify karta hai.
Question 2:
Assertion (A): Technology is derived from scientific principles.
Reason (R): Science provides the knowledge, while technology applies it.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Technology scientific principles se hi develop hoti hai. Science knowledge deta hai jaise electricity ke laws, aur technology usko apply karke devices banata hai jaise bulb. Reason (R) yeh difference clearly batata hai.
Question 3:
Assertion (A): All natural phenomena can be explained by physics alone.
Reason (R): Physics studies all natural laws comprehensively.
Correct Answer: (d) A is false and R is also false.
Explanation: Assertion (A) galat hai kyunki sabhi natural phenomena sirf physics se explain nahi ho sakte, jaise biological ya chemical processes ke liye alag sciences chahiye. Reason (R) bhi galat hai kyunki physics sirf physical laws ko study karta hai, na ki sabhi natural laws ko.
Question 4:
Assertion (A): Unification is a key aspect of physics.
Reason (R): It aims to explain diverse phenomena with few concepts.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Physics mein unification ka matlab hai alag-alag phenomena ko kam se kam concepts se explain karna, jaise electromagnetism mein electric aur magnetic forces ko unify kiya gaya. Reason (R) yeh sahi explain karta hai.
Question 5:
Assertion (A): Reductionism simplifies complex systems in physics.
Reason (R): It breaks down systems into simpler constituents.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Reductionism complex systems ko unke basic parts mein todkar samajhne ki koshish karta hai, jaise atoms ko study karke matter ke behavior ko samajhna. Reason (R) yeh process explain karta hai.
Question 6:
Assertion (A): Physics laws are universal.
Reason (R): They apply everywhere in the universe.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Physics ke laws jaise gravity ka law har jagah universe mein apply hote hain, Earth ho ya Moon. Reason (R) yeh universality clearly batata hai.
Question 7:
Assertion (A): Physics is limited to macroscopic phenomena.
Reason (R): Physics also studies microscopic phenomena like atoms.
Correct Answer: (c) A is false but R is true.
Explanation: Assertion (A) galat hai kyunki physics macroscopic (bade scale) ke saath microscopic (chhote scale jaise atoms) phenomena bhi study karta hai. Reason (R) sahi hai kyunki physics quantum mechanics jaise fields mein microscopic phenomena cover karta hai.
Question 8:
Assertion (A): Physics is an exact science.
Reason (R): It relies on precise mathematical formulations.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Physics ek exact science hai kyunki yeh mathematical equations aur precise measurements par based hai, jaise Newton’s laws ya E = mc². Reason (R) yeh mathematical basis explain karta hai.
Question 9:
Assertion (A): Scientific theories in physics are tentative.
Reason (R): They can be modified with new evidence.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Physics ke scientific theories temporary hote hain kyunki naye evidence se unko change ya improve kiya ja sakta hai, jaise Newtonian mechanics ko relativity ne modify kiya. Reason (R) yeh flexibility explain karta hai.
Question 10:
Assertion (A): Physics contributes to technological advancements.
Reason (R): Discoveries like electricity have led to modern devices.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Physics ke discoveries jaise electricity ya semiconductors ne technology ko revolutionize kiya hai, jaise computers aur lights. Reason (R) specific examples dekar yeh batata hai.
Chapter 2: Units and Measurements
Question 1:
Assertion (A): When we change the unit of measurement of a quantity, its numerical value changes.
Reason (R): Smaller the unit of measurement, smaller is its numerical value.
Correct Answer: (c) A is true but R is false.
Explanation: Jab hum kisi quantity ka unit change karte hain, to uska numerical value badal jata hai kyunki numerical value unit ke inversely proportional hota hai. Lekin Reason (R) galat hai kyunki smaller unit hone par numerical value bada hota hai, na ki chhota. Jaise, 1 meter = 100 cm, yahan meter se centimeter mein convert karne par numerical value 1 se 100 ho jata hai.
Question 2:
Assertion (A): Light year is a unit for measuring distance.
Reason (R): Light year is the distance that light travels with a velocity of 3×10⁸ m/s in one year.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Light year ek distance ka unit hai jo astronomical distances ko measure karne ke liye use hota hai. Reason (R) sahi hai kyunki light year woh distance hai jo prakash ek saal mein 3×10⁸ m/s ki speed se cover karta hai. Yeh Assertion (A) ko sahi tarah explain karta hai.
Question 3:
Assertion (A): The SI system is a coherent system of units.
Reason (R): Derived units are obtained from base units without numerical factors.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: SI system coherent hai kyunki isme derived units (jaise newton = kg m/s²) base units se bina kisi numerical factor ke banaye jaate hain. Reason (R) yeh coherence ka basis explain karta hai.
Question 4:
Assertion (A): Dimensional analysis can check the correctness of a physical equation.
Reason (R): Both sides of an equation must have the same dimensions.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Dimensional analysis se hum check kar sakte hain ki ek equation dimensionally consistent hai ya nahi. Reason (R) yeh batata hai ki equation ke dono sides ke dimensions same hone chahiye, jo Assertion (A) ko explain karta hai.
Question 5:
Assertion (A): Significant figures indicate the precision of a measurement.
Reason (R): More significant figures mean higher precision.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Significant figures measurement ki precision ko show karte hain. Zyada significant figures ka matlab hai ki measurement zyada precise hai. Reason (R) yeh relation clearly batata hai.
Question 6:
Assertion (A): Absolute error is always positive.
Reason (R): It is the magnitude of the difference between true and measured values.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Absolute error hamesha positive hota hai kyunki yeh true value aur measured value ke difference ka magnitude hota hai. Reason (R) yeh definition clearly deta hai.
Question 7:
Assertion (A): Relative error is dimensionless.
Reason (R): It is the ratio of absolute error to the measured value.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Relative error dimensionless hota hai kyunki yeh absolute error ko measured value se divide karke milta hai, jisse dimensions cancel ho jate hain. Reason (R) yeh process batata hai.
Question 8:
Assertion (A): Parallax method is used to measure large distances.
Reason (R): It measures the angle subtended by an object at two different points.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Parallax method astronomical distances jaise stars ke distance measure karne ke liye use hota hai, jisme object ke do alag points se angle measure kiya jata hai. Reason (R) yeh method explain karta hai.
Question 9:
Assertion (A): In addition or subtraction, the result has the same number of decimal places as the least precise number.
Reason (R): Precision is determined by the least precise measurement.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Addition ya subtraction mein result ke decimal places us number ke equal hote hain jisme least decimal places hote hain. Reason (R) yeh batata hai ki precision least precise measurement se decide hoti hai.
Question 10:
Assertion (A): Astronomical unit (AU) measures interplanetary distances.
Reason (R): 1 AU is the average distance between Earth and Sun.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Astronomical unit (AU) solar system mein distances measure karne ke liye use hota hai, aur 1 AU Earth aur Sun ke beech average distance (~150 million km) hai. Reason (R) isko define karta hai.
Chapter 3: Motion in a Straight Line
Question 1:
Assertion (A): Displacement of a body may be zero when distance travelled is not zero.
Reason (R): Displacement is the shortest distance between initial and final positions.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Displacement ek vector quantity hai jo initial aur final position ke beech shortest distance ko represent karta hai. Agar koi body circular path mein chalta hai aur wapas starting point par aata hai, to displacement zero hoga jabki distance zero nahi hoga. Reason (R) yeh clearly explain karta hai.
Question 2:
Assertion (A): The speedometer of a car measures instantaneous speed.
Reason (R): Average velocity is total displacement divided by total time.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Speedometer instantaneous speed measure karta hai, isliye Assertion (A) sahi hai. Reason (R) bhi sahi hai kyunki average velocity total displacement ko total time se divide karke milti hai. Lekin R, A ka explanation nahi hai kyunki speedometer ka average velocity se koi direct connection nahi hai.
Question 3:
Assertion (A): Velocity can be zero even if speed is not zero.
Reason (R): Velocity is a vector, and speed is a scalar.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Velocity zero ho sakti hai jab direction change hoti hai (jaise circular motion mein), lekin speed non-zero rahta hai. Reason (R) sahi hai kyunki velocity vector aur speed scalar hai, lekin yeh zero velocity ka direct reason nahi hai; actual reason direction change hai.
Question 4:
Assertion (A): In uniform motion, acceleration is zero.
Reason (R): Velocity is constant in uniform motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Uniform motion mein velocity constant hoti hai, isliye acceleration (rate of change of velocity) zero hota hai. Reason (R) yeh clearly explain karta hai.
Question 5:
Assertion (A): The area under velocity-time graph gives displacement.
Reason (R): Displacement is velocity multiplied by time for uniform motion.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Velocity-time graph ke neeche ka area displacement deta hai, chahe motion uniform ho ya non-uniform (integration se). Reason (R) sahi hai lekin sirf uniform motion ke liye, isliye yeh poora explanation nahi deta.
Question 6:
Assertion (A): For a freely falling body, acceleration is constant.
Reason (R): Acceleration due to gravity is constant near Earth’s surface.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Freely falling body par acceleration gravity (g) ke karan hota hai, jo Earth ke surface par constant (~9.8 m/s²) hai. Reason (R) yeh constant nature explain karta hai.
Question 7:
Assertion (A): Relative velocity can be greater than individual velocities.
Reason (R): Relative velocity is the vector difference of two velocities.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Relative velocity do objects ke velocities ka vector difference hai. Agar do objects opposite direction mein move kar rahe hain, to relative velocity unke individual velocities se badi ho sakti hai. Reason (R) yeh vector nature explain karta hai.
Question 8:
Assertion (A): Position-time graph for uniform motion is a straight line.
Reason (R): The slope of position-time graph gives velocity.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Uniform motion mein position-time graph straight line hota hai kyunki velocity constant hoti hai. Is graph ka slope velocity deta hai, jo Reason (R) mein explain kiya gaya hai.
Question 9:
Assertion (A): Average speed and average velocity are always equal in straight-line motion.
Reason (R): In straight-line motion without direction change, distance equals displacement.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Agar straight-line motion mein direction change na ho, to distance aur displacement equal hote hain, isliye average speed aur average velocity bhi equal hote hain. Reason (R) yeh condition explain karta hai.
Question 10:
Assertion (A): Acceleration-time graph for uniform motion is a horizontal line.
Reason (R): Acceleration is zero in uniform motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Uniform motion mein acceleration zero hota hai, isliye acceleration-time graph ek horizontal line (y = 0) hota hai. Reason (R) yeh zero acceleration ka concept explain karta hai.
Chapter 4: Motion in a Plane
Question 1:
Assertion (A): A body dropped from a given height and another body projected horizontally from the same height strike the ground simultaneously.
Reason (R): Horizontal velocity has no effect in the vertical direction.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Jab ek body drop kiya jata hai aur doosra same height se horizontally project kiya jata hai, dono ka vertical motion sirf gravity par depend karta hai. Horizontal velocity vertical motion ko affect nahi karta, isliye dono bodies ek hi time par ground par strike karte hain. Reason (R) iska sahi explanation deta hai.
Question 2:
Assertion (A): Vector addition is commutative.
Reason (R): Two vectors may be added graphically using head-to-tail method or parallelogram method.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Vector addition commutative hota hai, yani A + B = B + A, isliye Assertion (A) sahi hai. Reason (R) bhi sahi hai kyunki vectors ko head-to-tail ya parallelogram method se add kiya ja sakta hai. Lekin Reason (R) Assertion (A) ke commutativity ka explanation nahi deta, kyunki methods ka mention karna commutative property ko justify nahi karta.
Question 3:
Assertion (A): The path of a projectile is parabolic.
Reason (R): Projectile motion is a combination of horizontal uniform motion and vertical accelerated motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Projectile ka path parabolic hota hai jab air resistance na ho, kyunki yeh horizontal mein constant velocity aur vertical mein gravitational acceleration ke combination se banta hai. Reason (R) yeh clearly explain karta hai.
Question 4:
Assertion (A): The time of flight of a projectile depends on its initial velocity.
Reason (R): Time of flight is determined only by the vertical component of initial velocity.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Time of flight (T = 2u sinθ/g) initial velocity ke vertical component (u sinθ) par depend karta hai, na ki horizontal component par. Reason (R) yeh batata hai ki sirf vertical component matter karta hai, jo Assertion (A) ko explain karta hai.
Question 5:
Assertion (A): The range of a projectile is maximum when the angle of projection is 45°.
Reason (R): Range is given by R = (u² sin2θ)/g, and sin2θ is maximum at θ = 45°.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Projectile ka range formula R = (u² sin2θ)/g se milta hai, aur sin2θ maximum (1) hota hai jab θ = 45°. Isliye maximum range 45° par hota hai. Reason (R) yeh mathematical basis deta hai.
Question 6:
Assertion (A): The horizontal range is same for two angles of projection if they are complementary.
Reason (R): sin2θ = sin2(90° - θ).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Range formula mein sin2θ hota hai, aur sin2θ = sin2(90° - θ), isliye angles θ aur (90° - θ) ke liye range same hota hai. Reason (R) yeh trigonometric identity explain karta hai.
Question 7:
Assertion (A): In circular motion, velocity is always tangential to the path.
Reason (R): The centripetal acceleration is perpendicular to the velocity.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Circular motion mein velocity hamesha path ke tangential hoti hai, yeh Assertion (A) sahi hai. Reason (R) bhi sahi hai kyunki centripetal acceleration velocity ke perpendicular hoti hai. Lekin R, A ka direct explanation nahi hai kyunki tangential velocity ka reason path ki geometry hai, na ki acceleration ka direction.
Question 8:
Assertion (A): Centripetal force is a real force.
Reason (R): It is provided by tension, gravity, or friction in circular motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Centripetal force real force hai jo circular motion ke liye center ki taraf act karta hai, aur yeh tension, gravity, ya friction se provide hota hai. Reason (R) yeh sources batata hai jo A ko explain karta hai.
Question 9:
Assertion (A): In uniform circular motion, kinetic energy is constant.
Reason (R): Speed remains constant in uniform circular motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Uniform circular motion mein speed constant hota hai, aur kinetic energy (K.E. = ½ mv²) speed par depend karta hai, isliye kinetic energy bhi constant rahta hai. Reason (R) yeh explain karta hai.
Question 10:
Assertion (A): Angular velocity is same for all points on a rigid body in circular motion.
Reason (R): All points on a rigid body rotate through the same angle in the same time.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Rigid body mein sabhi points ek hi angular velocity (ω = θ/t) se rotate karte hain kyunki sab same angle ko same time mein cover karte hain. Reason (R) yeh clearly batata hai.
Chapter 5: Laws of Motion
Question 1:
Assertion (A): No force is required to move a body uniformly along a straight line.
Reason (R): Because F = ma = m(0) = 0.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Newton’s first law ke according, agar koi body uniformly straight line mein move kar rahi hai (constant velocity), to uspar koi net force nahi lagta. Reason (R) yeh batata hai ki F = ma, aur uniform motion mein acceleration (a) zero hota hai, isliye force (F) bhi zero hota hai. Yeh Assertion (A) ka sahi explanation hai.
Question 2:
Assertion (A): A rocket moves forward by pushing the surrounding air backwards.
Reason (R): It derives the necessary thrust to move forward according to Newton's third law of motion.
Correct Answer: (c) A is true but R is false.
Explanation: Rocket ke forward motion ka reason exhaust gases ka backward ejection hai, na ki surrounding air ko push karna, isliye Assertion (A) galat hai. Reason (R) sahi hai kyunki rocket ka thrust Newton’s third law (action-reaction) se milta hai, jab exhaust gases backward direction mein nikalte hain.
Question 3:
Assertion (A): Friction always opposes motion.
Reason (R): Friction acts opposite to the direction of relative motion between surfaces.
Correct Answer: (c) A is true but R is false.
Explanation: Assertion (A) galat hai kyunki friction hamesha motion ke against nahi hota, jaise walking mein friction forward motion ko help karta hai. Reason (R) sahi hai kyunki friction relative motion ke opposite act karta hai.
Question 4:
Assertion (A): Newton’s second law is the real law of motion.
Reason (R): It can derive both first and third laws.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Newton’s second law (F = ma) se first law (a = 0 to F = 0) aur third law (action-reaction) derive kiye ja sakte hain. Reason (R) yeh batata hai ki second law fundamental hai.
Question 5:
Assertion (A): Impulse is equal to change in momentum.
Reason (R): Impulse is the product of force and time.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Impulse (J = F × t) momentum ke change (Δp = mΔv) ke barabar hota hai, Newton’s second law se (F = Δp/Δt). Reason (R) yeh define karta hai.
Question 6:
Assertion (A): Action and reaction forces act on different bodies.
Reason (R): Newton’s third law states they are equal and opposite.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Newton’s third law ke according, action aur reaction forces alag bodies par act karte hain aur equal aur opposite hote hain. Reason (R) yeh law explain karta hai.
Question 7:
Assertion (A): Static friction is self-adjusting.
Reason (R): It adjusts its value up to a maximum limit to prevent motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Static friction force apne aap adjust hota hai applied force ke according, lekin maximum limit (μN) tak. Reason (R) yeh property batata hai.
Question 8:
Assertion (A): Momentum is conserved in an isolated system.
Reason (R): No external forces act on an isolated system.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Isolated system mein koi external force nahi hota, isliye Newton’s laws se momentum conserve hota hai. Reason (R) yeh condition batata hai.
Question 9:
Assertion (A): A body can be in equilibrium under concurrent forces.
Reason (R): Sum of forces must be zero for equilibrium.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Concurrent forces ke under body equilibrium mein ho sakti hai agar net force zero ho. Reason (R) yeh condition batata hai.
Question 10:
Assertion (A): Coefficient of friction is dimensionless.
Reason (R): It is the ratio of frictional force to normal force.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Coefficient of friction (μ) dimensionless hai kyunki yeh frictional force aur normal force ka ratio hai, dono ke dimensions same hote hain. Reason (R) yeh explain karta hai.
Chapter 6: Work, Energy, and Power
Question 1:
Assertion (A): Work done in moving a body over a closed loop is zero for a conservative force.
Reason (R): Conservative forces are path-independent.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Conservative force (jaise gravity) ke liye closed loop mein work done zero hota hai kyunki work sirf initial aur final position par depend karta hai, path par nahi. Reason (R) yeh path-independence explain karta hai.
Question 2:
Assertion (A): The kinetic energy of a body can never be negative.
Reason (R): Kinetic energy is given by K.E. = ½ mv², where m and v² are always positive.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Kinetic energy ka formula K.E. = ½ mv² hai, jahan mass (m) hamesha positive hota hai aur velocity square (v²) bhi positive ya zero hota hai. Isliye kinetic energy kabhi negative nahi ho sakti. Reason (R) yeh clearly explain karta hai.
Question 3:
Assertion (A): Work done by friction is always negative.
Reason (R): Friction always opposes the relative motion between two surfaces.
Correct Answer: (c) A is false but R is true.
Explanation: Friction ka work done hamesha negative nahi hota, jaise jab friction motion ke direction mein help karta hai (e.g., walking mein). Reason (R) sahi hai kyunki friction relative motion ke opposite act karta hai, lekin yeh A ke liye complete explanation nahi hai kyunki A galat hai.
Question 4:
Assertion (A): The work-energy theorem applies to both conservative and non-conservative forces.
Reason (R): Work done equals the change in kinetic energy.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Work-energy theorem (net work = change in K.E.) dono conservative (jaise gravity) aur non-conservative (jaise friction) forces ke liye apply hota hai. Reason (R) yeh theorem ka basic principle batata hai.
Question 5:
Assertion (A): Potential energy is defined only for conservative forces.
Reason (R): Potential energy depends on the path taken by the object.
Correct Answer: (c) A is true but R is false.
Explanation: Potential energy sirf conservative forces (jaise gravity) ke liye defined hoti hai kyunki yeh path-independent hoti hai. Reason (R) galat hai kyunki potential energy path par depend nahi karti, sirf position par.
Question 6:
Assertion (A): Mechanical energy is conserved in the absence of non-conservative forces.
Reason (R): Total mechanical energy is the sum of kinetic and potential energy.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Jab non-conservative forces (jaise friction) nahi hote, to mechanical energy (K.E. + P.E.) conserve hoti hai. Reason (R) sahi hai kyunki mechanical energy K.E. aur P.E. ka sum hai, lekin yeh conservation ka reason nahi batata, jo hai absence of non-conservative forces.
Question 7:
Assertion (A): Power is the rate of doing work.
Reason (R): Power is measured in watts, which is joules per second.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Power work done ka rate hai (P = W/t). Reason (R) yeh define karta hai ki power watt mein measure hoti hai, jo joules per second hai, aur yeh A ko explain karta hai.
Question 8:
Assertion (A): In an elastic collision, both momentum and kinetic energy are conserved.
Reason (R): No energy is lost to heat or deformation in an elastic collision.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Elastic collision mein momentum aur kinetic energy dono conserve hote hain kyunki koi energy heat ya deformation mein nahi jati. Reason (R) yeh conservation ka reason batata hai.
Question 9:
Assertion (A): In an inelastic collision, kinetic energy is not conserved.
Reason (R): Some kinetic energy is lost to heat or deformation.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Inelastic collision mein kinetic energy conserve nahi hoti kyunki kuch energy heat ya deformation mein chali jati hai. Reason (R) yeh loss explain karta hai.
Question 10:
Assertion (A): Work done by a force is zero if displacement is perpendicular to the force.
Reason (R): Work is given by W = F × d × cosθ.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Work ka formula W = F × d × cosθ hai. Agar displacement force ke perpendicular hai (θ = 90°), to cos90° = 0, aur work zero hota hai. Reason (R) yeh formula batata hai.
Chapter 7: System of Particles and Rotational Motion
Question 1:
Assertion (A): The center of mass of a system moves as if all mass is concentrated at that point.
Reason (R): External forces act on the center of mass.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Center of mass aise move karta hai jaise system ka saara mass usi point par concentrated ho. Reason (R) yeh batata hai ki external forces center of mass par act karti hain, jo is motion ko explain karta hai.
Question 2:
Assertion (A): Angular momentum is conserved if no external torque acts.
Reason (R): Angular momentum is given by L = Iω.
Correct Answer: (b) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Agar koi external torque nahi hai, to angular momentum conserve hota hai (law of conservation). Reason (R) sahi hai kyunki angular momentum ka formula L = Iω hai, lekin yeh conservation ka reason nahi batata.
Question 3:
Assertion (A): Moment of inertia depends on the distribution of mass.
Reason (R): It is given by I = Σmr².
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Moment of inertia mass ke distribution par depend karta hai, kyunki yeh formula I = Σmr² se calculate hota hai, jahan r mass ka distance hai axis se. Reason (R) yeh formula deta hai.
Question 4:
Assertion (A): Torque is the rotational equivalent of force.
Reason (R): Torque causes angular acceleration.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Torque rotational motion mein force jaisa kaam karta hai (τ = Iα), jaise force linear acceleration deta hai. Reason (R) yeh batata hai ki torque angular acceleration ka cause hai.
Question 5:
Assertion (A): The center of mass may lie outside a body.
Reason (R): It depends on the mass distribution of the body.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Center of mass body ke bahar ho sakta hai, jaise ring ya hollow objects mein. Reason (R) yeh batata hai ki yeh mass ke distribution par depend karta hai.
Question 6:
Assertion (A): In pure rolling, there is no slipping.
Reason (R): The point of contact with the surface is at rest relative to the surface.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Pure rolling mein koi slipping nahi hoti kyunki contact point surface ke respect mein rest par hota hai. Reason (R) yeh condition explain karta hai.
Question 7:
Assertion (A): Angular velocity is the same for all points on a rigid body.
Reason (R): All points rotate through the same angle in the same time.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Rigid body mein sabhi points ek hi angular velocity (ω = θ/t) se rotate karte hain kyunki sab same angle ko same time mein cover karte hain. Reason (R) yeh clearly batata hai.
Question 8:
Assertion (A): The moment of inertia of a body is constant.
Reason (R): It depends only on the mass of the body.
Correct Answer: (c) A is false but R is false.
Explanation: Assertion (A) galat hai kyunki moment of inertia mass ke saath axis aur mass distribution par bhi depend karta hai, isliye constant nahi hota. Reason (R) bhi galat hai kyunki moment of inertia sirf mass par nahi, balki distribution par bhi depend karta hai.
Question 9:
Assertion (A): In rolling motion, total kinetic energy includes both translational and rotational components.
Reason (R): Total K.E. = ½ mv² + ½ Iω².
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Rolling motion mein total kinetic energy translational (½ mv²) aur rotational (½ Iω²) ka sum hota hai. Reason (R) yeh formula deta hai jo A ko explain karta hai.
Question 10:
Assertion (A): The angular acceleration is zero in uniform rotational motion.
Reason (R): Angular velocity is constant in uniform rotational motion.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Assertion (A): Gravitational force is a conservative force.
Reason (R): Work done by gravitational force is path-independent.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Gravitational force conservative hai kyunki iska work done path-independent hota hai, sirf initial aur final positions par depend karta hai. Reason (R) yeh property batata hai.
Question 2:
Assertion (A): The gravitational force between two masses is always attractive.
Reason (R): Gravitational force follows Newton’s universal law of gravitation.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Newton’s law of gravitation (F = GMm/r²) ke according, gravitational force hamesha attractive hoti hai. Reason (R) yeh law batata hai jo A ko explain karta hai.
Question 3:
Assertion (A): The value of g decreases with height above Earth’s surface.
Reason (R): g is inversely proportional to the square of the distance from Earth’s center.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Acceleration due to gravity (g) height badhne par kam hota hai kyunki g ∝ 1/r², jahan r Earth ke center se distance hai. Reason (R) yeh inverse-square law explain karta hai.
Question 4:
Assertion (A): The escape velocity from Earth depends on its mass.
Reason (R): Escape velocity is given by v = √(2GM/R).
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Escape velocity Earth ke mass (M) aur radius (R) par depend karta hai, jaisa formula v = √(2GM/R) se pata chalta hai. Reason (R) yeh formula deta hai.
Question 5:
Assertion (A): Gravitational potential energy is always negative.
Reason (R): It is defined as zero at infinity.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Gravitational potential energy (U = -GMm/r) hamesha negative hoti hai kyunki reference point infinity par zero liya jata hai. Reason (R) yeh convention batata hai.
Question 6:
Assertion (A): Satellites in circular orbits have constant speed.
Reason (R): The centripetal force is provided by gravitational force.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Circular orbit mein satellite ka speed constant hota hai kyunki gravitational force centripetal force provide karta hai. Reason (R) yeh mechanism batata hai.
Question 7:
Assertion (A): The time period of a satellite depends on its orbital radius.
Reason (R): Time period is given by T² ∝ r³.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Kepler’s third law ke according, satellite ka time period orbital radius (r) par depend karta hai, aur T² ∝ r³. Reason (R) yeh relation deta hai.
Question 8:
Assertion (A): Weightlessness is experienced in a freely falling lift.
Reason (R): The normal force on the body becomes zero.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Freely falling lift mein weightlessness isliye feel hoti hai kyunki normal force zero ho jati hai (sab free fall mein hai). Reason (R) yeh condition explain karta hai.
Question 9:
Assertion (A): Gravitational field intensity is zero at the center of Earth.
Reason (R): All mass contributions cancel out at the center.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Earth ke center par gravitational field intensity zero hoti hai kyunki saari mass ke contributions cancel ho jati hain. Reason (R) yeh cancellation batata hai.
Question 10:
Assertion (A): The gravitational force is the weakest fundamental force.
Reason (R): Its strength is much less compared to electromagnetic force.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Gravitational force sabse weak fundamental force hai, jabki electromagnetic force isse kafi strong hoti hai. Reason (R) yeh strength ka comparison deta hai.
Chapter 9: Mechanical Properties of Solids
Question 1:
Assertion (A): Elasticity is the property of a body to regain its original shape.
Reason (R): It is due to intermolecular forces.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Elasticity ek material ki property hai jo use original shape mein wapas aane deta hai deformation ke baad. Reason (R) yeh batata hai ki yeh intermolecular forces ke karan hota hai.
Question 2:
Assertion (A): Young’s modulus is defined for solids only.
Reason (R): It measures resistance to longitudinal deformation.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Young’s modulus sirf solids ke liye defined hota hai kyunki yeh longitudinal stress aur strain ka ratio hai. Reason (R) yeh definition batata hai.
Question 3:
Assertion (A): Stress is a scalar quantity.
Reason (R): Stress is force per unit area.
Correct Answer: (c) A is false but R is true.
Explanation: Stress scalar nahi, tensor quantity hai kyunki yeh direction bhi involve karta hai. Reason (R) sahi hai kyunki stress force per unit area (F/A) hai, lekin yeh A ko explain nahi karta.
Question 4:
Assertion (A): Hooke’s law is valid within the elastic limit.
Reason (R): Stress is directly proportional to strain in the elastic region.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Hooke’s law (stress ∝ strain) elastic limit tak valid hota hai. Reason (R) yeh proportionality batata hai jo A ko explain karta hai.
Question 5:
Assertion (A): Brittle materials have a small elastic region.
Reason (R): They break soon after the elastic limit is crossed.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Brittle materials (jaise glass) ka elastic region chhota hota hai kyunki elastic limit cross hone ke baad woh jaldi toot jate hain. Reason (R) yeh behavior batata hai.
Question 6:
Assertion (A): Poisson’s ratio is dimensionless.
Reason (R): It is the ratio of lateral strain to longitudinal strain.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Poisson’s ratio dimensionless hai kyunki yeh lateral strain aur longitudinal strain ka ratio hai, dono strain dimensionless hote hain. Reason (R) yeh definition deta hai.
Question 7:
Assertion (A): Ductile materials can undergo large plastic deformation.
Reason (R): They have a large plastic region before breaking.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Ductile materials (jaise copper) bada plastic deformation seh sakte hain kyunki unka plastic region bada hota hai. Reason (R) yeh property batata hai.
Question 8:
Assertion (A): Modulus of elasticity decreases with temperature.
Reason (R): Intermolecular forces weaken with increasing temperature.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Modulus of elasticity (jaise Young’s modulus) temperature badhne par kam hota hai kyunki intermolecular forces weak ho jati hain. Reason (R) yeh cause batata hai.
Question 9:
Assertion (A): Bulk modulus measures resistance to volume change.
Reason (R): It is the ratio of volume stress to volume strain.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Bulk modulus volume change ke resistance ko measure karta hai, aur yeh volume stress aur volume strain ka ratio hai. Reason (R) yeh definition deta hai.
Question 10:
Assertion (A): Elastic limit is the maximum stress a material can withstand without permanent deformation.
Correct Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Elastic limit woh maximum stress hai jahan tak material bina permanent deformation ke wapas aata hai. Reason (R) batata hai ki iske baad plastic deformation shuru hoti hai.
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