Question

Can an electron at rest in a magnetic field be set into motion by the magnetic field? What if it were at rest in an electric field?

Answer 1

By a magnetic field: no

By an electric field: yes

Step-by-step explanation:

The force exerted by a magnetic field on an electron is

`F=qvB sin \theta`

where

q is the electron charge

v is the speed of the electron

B is the strength of the magnetic field

`\theta` is the angle between the direction of v and B

As we see from the formula, if the electron is at rest, then v = 0, and therefore the force is also zero: F = 0. Therefore, the magnetic field cannot set the electron into motion.

On the other hand, the force exerted on an electron by an electric field does not depend on the speed:

`F=qE`

where E is the intensity of the electric field

Therefore, the electric force acts also when the electron is at rest, so it is able to set the electron into motion.