Question

A bar magnet when placed at an angle of `30^(@)` to the direction of magnetic field field induction of `5xx10^(-2)T`, experiences a moment of couple `25xx10^(-6) N-m`. If the length of the magnet is 5cm its pole strength is
A. `2xx10^(-2) A-m`
B. `5xx10^(-2) A-m`
C. `2 A-m`
D. `5 A-m`

Answer 1

Correct Answer - A
`tau= MB sin theta implies tau= (mL) B sintheta`
`implies 25xx10^(-6)=(mxx5xx10^(-2))xx5xx10^(-2)xx sin 30^(@)`
`implies m=2xx10^(-2) A-m`