Question

The current in an electron beam in a cathode ray tube is 7.0 X 10^-5 A. A beam of electrons is aimed at a screen. How much charge hits the screen in 5.0S?

A- 2.8X10^3 C

B-5.6X10^-2 C

C-3.5X10^-4 C

D-5.3X10^-6 C

Answer 1

The current I is defined as the quantity of charge Q that flows in the tube in the unit of time t:

`I = (Q)/(t)`
In our problem, we have
`I=7\cdot 10^(-5) A` and the time is t=5.0 s. Therefore we can find the charge that hits the screen during this time:

`Q=It =7\cdot 10^(-5) A \cdot 5.0 s=3.5X10^(-4) C`