Question

A small bar magnet has a magnetic moment 1.2 A-m². The magnetic field at a distance 0.1 m on its axis will be : (μ₀ = 4π × 10^–7 T-m/A)

• A. 1.2 × 10^–4 T
• B. 2.4 × 10^–4 T
• C. 2.4 × 10⁴ T
• D. 1.2 × 10⁴ T

Answer 1

Answer: (B)

2.4 × 10^–4 T

Answer 2

$B = \frac { \mu _ { 0 } } { 4 \pi } \cdot \frac { 2 M } { d ^ { 3 } } \Rightarrow B = 10 ^ { - 7 } \times \frac { 2 \times 1.2 } { ( 0.1 ) ^ { 3 } } = 2.4 \times 10 ^ { - 4 } \mathrm {~T}$