Question

The magnetic moment of a short bar magnet placed with its magnetic axis at `30^(@)` to an external field of 900 G and experiences a torque of 0.02 N m is
A. `0.35Am^(2)`
B. `0.44Am^(2)`
C. `2.45Am^(2)`
D. `1.5Am^(2)`

Answer 1

Correct Answer - B
Here, B=900, Gauss=`900xx10^(-4)T`
`=9xx10^(2)T`
`tau=0.02Nm and theta=30^(@)`
`Rightarrow 0.02=9xx10^(-2)xx(1)/(2)xxm`
`m=(0.02xx2)/(9xx10^(-2))=0.44Am^(2)`