Question

If a magnet of length 10 cm and pole strength 40 A-m is placed at an angle of 45^o in an uniform induction field of intensity 2 × 10^–4 T, the couple acting on it is

• A. 0.5656 × 10^–4 N-m
• B. 0.5656 × 10^–3 N-m
• C. 0.656 × 10^–4 N-m
• D. 0.656 × 10^–5 N-m

Answer 1

Answer: (B)

0.5656 × 10^–3 N-m

Answer 2

$\tau = M B \sin \theta = ( m L ) B \sin \theta$

$= \left( 40 \times 10 \times 10 ^ { - 2 } \right) \times 2 \times 10 ^ { - 4 } \times \sin 45 ^ { \circ }$

$= 0.565 \times 10 ^ { - 3 } N - m$