Question

A current carrying loop is placed in a uniform magnetic field. The torque acting on it does not depend upon –
Option:
A. Shape of the loop
B. Area of the loop
C. Value of the current
D. Magnetic Field

Answer 1

Hint: First think about the torque. After that, think about a formula to find the torque in a current carrying loop that is placed in a uniform magnetic field. Compare its relation with the options given then think about suitable options in which it does not depend.

Complete answer:
According to the question, we have given that A current carrying loop is placed in a uniform magnetic field. Now, when a current carrying loop having current i and let area of the loop is A then magnetic moment developed in it is given by $\mu = NiA$ where N is the number of turns of the given loop.

Now, when it’s placed in magnetic field B then a torque acts on it which is given by the relation
$\tau = \mu \times B$
$\tau = NiAB \sin \theta $

So, we see that torque depends upon current i, Number of turns N, magnetic field B and area of the loop A and we know that area does not depends upon the shape because two shape can have similar area. So, torque does not depends upon shape of the loop.

Hence, the correct answer is option A. Shape of the loop

Note: Torque is the product of the force vector and the perpendicular distance from the axis of rotation to the force vector. A coil of wire placed in a magnetic field will experience a torque, which is a force that causes rotational motion. The magnitude of the torque is proportional to the strength of the magnetic field and the current in the coil. The direction of the torque is perpendicular to the plane of the coil and the magnetic field. It also depends on the area of the current carrying loop. On another thing the magnitude of the torque is the angle of the magnetic moment with the plane of the current carrying loop.