Question

The work done in rotating a magnet of magnetic moment 2 A-m² in a magnetic field of 5 × 10^–3 T from the direction along the magnetic field to opposite direction to the magnetic field, is

• A. Zero
• B. 2 × 10^–2 J
• C. 10^–2 J
• D. 10 J

Answer 1

Answer: (B)

2 × 10^–2 J

Answer 2

$W = M B ( 1 - \cos \theta )$ where $\theta = 180 ^ { \circ }$