A beam of electrons passes underfected throgh unifromly perpendicular electric and magnetic fields. If the electric fiedl is swiched off, and the same magnetic field is mainted fiedl is maintetained the electrons move:

Options

A. in a eliptical orbit
B. in a circular orbit
C. along a parabolic path
D. along a straight line

Answer

B

Explanation

(b) If beam of electrons passes underflected then force due to electric field should be balanced with force due to magnetic fields `F_(e) = F_(m)`. But if electric field becomes zero, then only force due to magnetic field exists. Under this force, the charge moves along a circle.