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

Options

A. ` 2 xx 10^(-2)A-m`
B. `5 xx 10^(-2)A-m`
C. `2 A-m`
D. `5 A-m`

Answer

A

Explanation

As , `tau =MB sin theta `
` tau =m(2L) B sin theta `
`m=(tau)/((2l)B sin theta )=(25xx10^(-6))/((0.05)(5 xx 10^(-2))sin 30^(@))`
`= 2 xx 10^(-2) A-m`