Question

A closely wound solenoid of 2000 turns and area of cross-section 1.6 × 10⁻⁴ m^2, carrying a current of 4.0 A, 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 is the force and torque on the solenoid if a uniform horizontal magnetic field of 7.5 × 10⁻² T is set up at an angle of 30º with the axis of the solenoid?

Answer 1

Number of turns on the solenoid, n = 2000
Area ofcross-section of the solenoid, A = 1.6 × 10⁻⁴ m²

Current in the solenoid, I = 4 A
(a) The magnetic moment along the axis of the solenoid is calculated as: M = nAI
= 2000 × 1.6 × 10⁻⁴ × 4 = 1.28 Am²
(b) Magnetic field, B = 7.5 × 10⁻² T
Angle between the magnetic field and the axis of the solenoid, θ = 30°