Question

A moving charge will produce
A. No field
B. An electric field only
C. A Magnetic field only
D. Both (b) and (c)

Answer 1

Hint: As we know that static charge generates electric fields but when it is made into motion the observer in rest perceives it as a magnetic field. If the observer starts moving with the charge with the same velocity, then he can experience electrical interactions.

Complete step by step answer:
As we all know that it is a property of charge to produce an electric field. Now to understand its magnetic effect, let us take an example. Let us suppose, a positive charge is kept close to a current-carrying wire but the positive charge will not be affected by the current because inside the current-carrying wire, the electrons travel but the nucleus is at rest. But at any point in time, the net charge on the bulk volume is zero and hence the positive charge does not experience any force.
But if the positive charge is set into motion equal to the speed of electrons i.e. opposite to the direction of the current, we will see that the positive charge starts deflecting away from the wire and its reason in the magnetic effect of current in the wire which is given by the Lorentz force.

$\therefore$ The correct option is (D).

Note:
Here we can see that the field magnetism is something like adding electrostatics with the special theory of relativity. The magnetic field is just an electric field but it is an electric field in a different frame of reference. The magnetic field and electric field are the two different sides of the same page. We should keep in mind that a moving magnetic field gives rise to an electric field but also a moving electric field gives rise to a magnetic field.