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 an elliptical orbit
B. in a circular orbit
C. along a parabolic path
D. along a straight line

Answer

B

Explanation

If both electric and magnetic field are present and perpendicular to each other and the particle is moving perpendicular to both of them with `F_(e)=F_(m)`. In this situation `vec(E) ne 0` and `vec(B)ne0`
but if electric field becomes zero, then only force due to magnetic field exists. under this force, the charge moves along a circle.