An electric current i enters and leaves a uniform circular wire of radius a through diametrically opposite points. A charge particle q moving along the axis of the circular wire passes tough its center at speed v. The magnetic force acting on the particle when it passes through the center has a magnitude.
A.

B.

C.

D. zero

An electron is moving along the positive x-axis. You want to apply a magnetic field for a short time so that the electron may reverse its direction and move parallel to the negative x-axis. This can be done by applying the magnetic field along.

A charged particle is moved along a magnetic field line. The magnetic force on the particle is

The free electrons in a conducting wire are in constant thermal motion. If such a wire, carrying no current, is placed in a magnetic field, is there a magnetic force on each free electron? Is there a magnetic force on the wire?

Two ions have equal masses but one is singly ionized and the other is doubly ionized. They are projected from the same place in a uniform magnetic field with the same velocity perpendicular to the field.

Two wires carrying equal currents i each, are placed perpendicular to each other, just avoiding a contact. If one wire is held fixed and the other is free to move under magnetic forces, what kind of motion will result?

If a charged particle projected in a gravity-free room deflects,

You are facing a circular wire carrying an electric current. The current is clockwise a seen by you. Is the field at the centre coming towards you or going away from you?

The torque on a current loop is zero if the angel between the positive normal and the magnetic field is either θ = 0 or θ = 180°. In which of the two orientations, the equilibrium is stable?

The net charge in a current-carrying wire is zero. Then, why does a magnetic field exert a force on it?