Question

A closely wound solenoid of `2000` turns and area of cross-section `1.5 xx 10^(-4) m^(2)` carries a current of `2.0 A`. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field `5 xx 10^(-2)` tesla making an angle of `30^(@)` with the axis of the solenoid. The torque on the solenoid with the
A. `3 xx 10^(-3) N.m`
B. `1.5 xx 10^(-3) N.m`
C. `1.5 xx 10^(-2) N.m`
D. `3 xx 10^(-2) N.m`

Answer 1

Correct Answer - C

`M = NiA = 2000 xx 2 xx 1.5 xx 10^(-4) = 0.6 A-m^(2)`
`tau = MB sin 30^(@)`
`= 0.6 xx 5 xx 10^(-2) xx (1)/(2) = 1.5 xx 10^(-2) N-m`