Question

A charge ‘q’ moving along the X- axis with a velocity  `vecv` is subjected to a uniform magnetic field B along the Z-axis as it crosses the origin O.

(i) Trace its trajectory.

(ii) Does the charge gain kinetic energy as it enters the magnetic field? Justify your answer.

Answer 1

(i)

The direction of magnetic field is along the negative X-direction. Hence, the magnetic force will act in such a way that this particle describes a circular motion as shown below.

(ii) No, the charge does not gain kinetic energy because the force and velocity are perpendicular to each other.

`W = vecF.vecv =Fvcostheta`

`theta = 90°`

Thus, force does not bring out any change in the velocity.