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)Nm`
B. `0.5656xx10^(-3) Nm`
C. `0.65 xx10^(-4)Nm`
D. `0.66xx10^(4)Nm`

Answer 1

Correct Answer - B
`2l=10cm,m=40Am0=45^(@),B=2xx10^(-4)T tau=?`br`tau=MB sin theta=m2l B sintheta`
`40xx10xx10^(-2)xx2xx10^(-4)xxsin45`
`0.5656xx10^(-3) Nm`