Question

If a charged particle kept at rest experiences an electromagnetic force,
(a) the electric field must not be zero
(b) the magnetic field must not be zero
(c) the electric field may or may not be zero
(d) the magnetic field may or may not be zero

Answer 1

(a) the electric field must not be zero
(d) the magnetic field may or may not be zero

As the charged particle is at rest, its velocity, V = 0 and magnetic force, F = qVB = 0. Hence, we cannot determine whether a magnetic field is present or not. But as the particle at rest experiences an electromagnetic force, the electric field must be non-zero. As electric force acts on a particle, whether it is at rest or in motion, an electric force must be present.