Question

 An electron gun in a TV set shoots out a beam of electrons. The beam current is 2.1µA. How many electrons strike the TV screen for 5 seconds? How much charge strikes the screen in a minute?

Answer 1

$I=q/t\to I=ne/t\to n=It/e=2.1\cdot10^{-6}\cdot5/(1.6\cdot10^{-19})=65625\cdot10^9$ (electrons).

$q=It=2.1\cdot10^{-6}\cdot60=126\ (\mu C)$ . Answer