A closely wound solenoid of 2000 turns and area of cross section `1.6xx10^-4m^2`, carrying a current of `4amp.` is suspended through its centre allowing it to turn in a horizontal plane:
(a) What is the magnetic moment associated with the solenoid?
(b) What are the force and torque on the solenoid if a uniform horizontal magnetic field of `7*5xx10^-2T` is set up at an angle of `30^@` with the axis of the solenoid?

Explanation

(a) `1.28A m^(-2)` along the axis in the direction related to the sence of current via the right handed screw rule.
(b) Forces is zero in uniform field torque = 0.048 Nm in a direction that tends to align the axis of the solenodi (i.e., its magnitude moment vector) along B.