Question

A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move

• A. in an elliptical orbit
• B. in a circular orbit
• C. along a parabolic path
• D. along a staight line

Answer 1

The correct option is B in a circular orbit

A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, comment about the path of the electron,in a circular orbit

$F_{centri}=F_{magnetic}$

$m{v}^2/r=qBv$

$r=\frac{qB}{mv}$