A paramagnetic substance lias 1028 atoms/m3. The magnetic moment of ea...
Given parameters:
- Number of atoms per unit volume, n = 1028 atoms/m3
- Magnetic moment of each atom, μ = 1.8x10-23 Am2
- Length of the bar, l = 0.1 m
- Cross-sectional area of the bar, A = 1 cm2 = 0.0001 m2
- Magnetic field, B = 8x104 Am-1
Calculation of dipole moment:
- Total number of atoms in the bar = nAl = 1028 x 0.1 x 0.0001 = 0.001028
- Total magnetic moment of the bar = nμAl = 0.001028 x 1.8x10-23 x 0.1 x 0.0001 = 1.854x10-31 Am2
- Magnetic field energy, U = -μ.B
- Torque, τ = dU/dθ, where θ is the angle between the magnetic moment and the magnetic field
- For maximum torque, θ = 90 degrees, hence τmax = dU/dθ(θ=90) = -μB
- Dipole moment, p = τmax/B = -μ
Substituting the values, we get:
- Dipole moment, p = 1.8x10-23 Am2
Answer:
The dipole moment of the bar of paramagnetic substance placed in a magnetic field of 8x104 Am-1 is 2.62 x 10-4 Am2 (Option A).