A cathode ray tube (CRT) is a device that produces a focused beam of electrons i

Question

A cathode ray tube (CRT) is a device that produces a focused beam of electrons in a vacuum. The electrons strike a phosphor-coated glass screen at the end of the tube, which produces a bright spot of light. The position of the bright spot of light on the screen can be adjusted by deflecting the electrons with electrical fields, magnetic fields, or both. Although the CRT tube was once commonly found in televisions, computer displays, and oscilloscopes, newer appliances use a liquid crystal display (LCD) or plasma screen. You still may come across CRT in your studs of science. Consider a CRT with an electron beam average current of 25.00 mu A. How many electrons strike the screen every minute?

Explanation / Answer

step;1

Given that

current i=24*10^-6 A

time t=60 sec

step;2

now we find the charge

charge Q=25*60*10^-6=1.5*10^-3 C

step;3

now we find the number of the electrons strike the screen

Q=ne

1.5*10^-3=n*1.6*10^-19

number of the electrons n=9.375*10^15 electrons

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