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. $1.5$N m
• B. $2.5$N m
• C. $3.5$ N m
• D. zero

Answer 1

Answer: (D)

zero

Here, n = $25$ turns, r = $12$cm, B = $0.5$T
Since the coil is placed in uniform magnetic field normal to the place of the coil. Hence the angle between magnetic moment and magnetic field direction is zero $(i.e.\theta =0)$
$therefore=mBsin\theta =mBsin0$
$\therefore T=0$