Question

A circular coil of 25 turns and radius of 12 cm is placed in a uniform magnetic field of 0.5 T normal to the plane of coil. If the current in the coil is 5 A, then total torque experienced by the coil is

• A. 1.5 Nm
• B. 2.5 N m
• C. 3.5 N m
• D. Zero

Answer 1

Answer: (D)

Zero

Answer 2

: Here, n = 25 turns, r = 12 cm, $B = 0.5 T$

Since the coil is placed in uniform magnetic field normal to the plane of the coil.

Hence the angle between magnetic moment and magnetic field direction is zero

(i.e.,$\theta = 0$)

$\therefore \tau = \mathrm { mB } \sin \theta = \mathrm { mB } \sin \theta$

$\Rightarrow \tau = 0$