A circular loop of radius a, carrying a current I, is placed in a tow dimensional magnetic field. The centre of the loop coincides with the centre of the filed The strenght of the magnetic field at the pariphery of the loop is B. find the magnetic force on the wire.

Options

A. Smaller loop experiences a net force.
B. Smaller loop experiences a netforce and torque.
C. Smaller loop experiences a net torque.
D. Smaller loop experiences no force and no torque.

Answer

c

Explanation

Magnetic field of the bigger coil will be along its axis and hence perpendicular to the magnetic moment vector of the smaller coil, which is along the axis of the smaller coil. Note that it is given that the plane of the smaller coil is kept perpendicular to the plane of the bigger coil. Torque is given by `vec tau = vec mu xx vecB` and hence the smaller coil will experience maximum torque as `theta = 90^(@)`. Moreover, it is given that the smaller coil is very small in size and hence we may assume it to be placed in an almost uniform field, so it will not experience any force. Thus, option (c) is correct.