Question

A force 4.6 x 10 -14 N acts on a particle of unknown charge moving perpendicularly through a magnetic field of 9 mT. if the speed of the particle is 2x104 m/s, what is the charge of the particle?

Answer 1

According to the famous law:

$$F=qvB,\\\space\\ q=F/(vB)=2.56·10^{-16}\text{ C}.$$