The current traveling from the cathode to the screen in a television picture tube is #5.0 times 10^-5# ampere. How many electrons strike the screen in 5.0 seconds?

Question

9312 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-12-29T18:58:40

#(It)/e#

By definition, electric current is net amount of charges passing through the cross-section of a conductor:

I = #Q/t#

Q= charge
I = current
t = time
e = 1.602#xx10^-19# C, charge carried by one electron.

The total amount of charges crossing an a cross-section is:

Q = I t

Since each electron carries only 1 e charge, then there must be #Q/e# electrons:

Number of electrons = #Q/e = (I t)/e #

Answer 2 · 2017-12-29T19:29:53

#1.56xx10^15" electrons"#

Given:

#(5.00 xx 10^-5" A")/1#

The definition of an Ampere is #1" A"= (1" C/s")#

#(5.00 xx 10^-5" C")/(1" s")#

We are also given that the time interval is #5" s"#:

#(5.00 xx 10^-5" C")/(1" s")(5" s")/1#

The conversion factor from Coulombs to electrons is #(6.242xx10^18" electrons")/"C"#

#(5.00 xx 10^-5" C")/(1" s")(5" s")/1(6.242xx10^18" electrons")/"C" = 1.56xx10^15" electrons"#