Magnetic Field & Magnetisation
and Curie’s Law
1. Magnetic Field and Magnetisation
Material ke andar effective magnetic field B ka formula:
B = μ₀ (H + M)
Where:
- B = Magnetic field (Tesla)
- H = Magnetising field (A/m)
- M = Magnetisation
- μ₀ = 4π × 10⁻⁷ T·m/A
Magnetisation & Susceptibility
M = χ H
Substitute M = χH inside B = μ₀(H + M):
B = μ₀H(1 + χ)
Thus permeability:
μ = μ₀(1 + χ)
So,
B = μH
Example 1: Calculate B
Given: χ = 0.004, H = 1000 A/m
1) Magnetisation:
M = χH = 0.004 × 1000 = 4 A/m
2) Magnetic Field:
B = μ₀(H + M) = 4π × 10⁻⁷ × 1004 ≈ 1.26 × 10⁻³ T
2. Curie’s Law
Paramagnetic materials ke liye:
χ = C / T
Temperature ↑ → Susceptibility ↓
Example 2: Curie’s Law
Given: C = 0.8 K
At T₁ = 200 K:
χ₁ = 0.8 / 200 = 0.004
At T₂ = 400 K:
χ₂ = 0.8 / 400 = 0.002
Result: Temperature doubles → χ half.