A coil of 150 turns of wire is in the form of a circle,carries a current of 63 mA,and sits in the center of a dipole magnet that produces a uniform magnetic field of strength 1.5 T.The torque on the coil has a maximum value of 0.25 Nm.What is the radius of the coils?
A) 9.2 cm
B) 13 cm
C) 0.56 cm
D) 7.5 cm

Question

Quizplus · Accepted Answer

The torque on a current-carrying coil in a magnetic field is given by τ = nIABsinθ. For maximum torque, sinθ = 1. Rearranging for A, we have A = τ / (nIB). Substituting the given values (τ = 0.25 Nm, n = 150, I = 0.063 A, B = 1.5 T), we find A = 0.025 m². Since A = πr², solving for r gives r ≈ 0.075 m or 7.5 cm.

A Coil of 150 Turns of Wire Is in the Form