Question

If a magnet of length `10cm` and pole strength `40 A-m` is placed at an angle of `45^(@)` in an uniform induction field of intensity `2xx10^(-4)T`, the couple acting on it is
A. `0.5656xx10^(-4)N-m`
B. `0.5656xx10^(-3)N-m`
C. `0.656xx10^(-4)N-m`
D. `0.656xx10^(-5)N-m`

Answer 1

Correct Answer - B
`tau=MB sintheta=(mL) B sintheta`
`=(40xx10xx10^(-2))xx2xx10^(-4)xx sin 45^(@)`
`=0.565xx10^(-3) N-m`