Question

A circular coil of radius $r = 10\text{ cm}$ having $300$ turns carries a current of $2\text{ A}$. The coil is suspended vertically in a uniform magnetic field of strength $7\text{ T}$. If the plane of the coil makes an angle of $30^\circ$ with the magnetic field, the torque needed to prevent it from turning is:

• A. $22.84\text{ N m}$
• B. $1.1\text{ N m}$
• C. $5.71\text{ N m}$
• D. $11.42\text{ N m}$

Hint:

Always check the wording for angles in magnetic torque questions. If it says "angle with the normal to the plane", use $\sin\theta$. If it says "angle with the plane of the coil", use $\cos\alpha$ directly!

Answer 1

The Correct Option is D