Question

A charged particle moves along a circle under the action of possible constant electric and magnetic fields. Which of the following is possible?
(a) E = 0, B = 0
(b) E = 0, B ≠ 0
(c) E ≠ 0, B = 0
(d) E ≠ 0, B ≠ 0

Answer 1

The answer for this question is (b) B ≠ 0, E = 0

Explanation:

• A force q E is exerted by the electric field on the charged particle that accelerates always, i.e., it increases the particle’s speed. By the electric field, the particle can never be rotated in a circle.
• This is because there will be a continuous increase due to acceleration. So, the options (d) and (c) are incorrect.
• The magnitude of the velocity cannot be changed the magnetic field, but changes only the velocity of the direction.
• If the particle moves in a circle it means that the speed should start for year. The only direct velocity is constant and only the change be b can be achieved. So, B ≠ 0 and E = 0.