A particle moves in a gravity free space where an electric field of strength E and a magnetic field of induction B exit. Which of the following statement is are correct?

Options

A. If `E!=0 and B!=0`, velocity of the particle may remains constant
B. If E=0, the particle cannot trace a circular path
C. If E=0, the kinetic energy of the particle remains constant
D. None of these

Answer

(a,c)

Explanation

(a) Velocity of the particle can be constant if the electric force
balances the magnetic forces, i.e, `qvecE=qvecvxxvecB`.
(b) If E=0, the particle can trace circular path if `vbotB`.
(c) If E=0, kinetic energy remains constant, because magnetic
force is not doing any work.