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Van de Graaff generator energy question

I would appreciate help with this problem:
If a Van de Graaff generator is charged to 50,000 volts, how much
energy does it take to add an additional electron to the charge on the
sphere? (I know that the charge on an electron is -1.6 x 10^-19 C)
Thanks
 

Chi Meson

Science Advisor
Homework Helper
1,767
10
A volt is a "joule/coulomb"

You got volts, you got coulombs, you want joules.
 
So I multiplied 50000 x -1.6x10^-19
and I get for an answer: -8x10^-18 joules
Does that look right?
 

OlderDan

Science Advisor
Homework Helper
3,021
1
Aprilshowers said:
So I multiplied 50000 x -1.6x10^-19
and I get for an answer: -8x10^-18 joules
Does that look right?
Your exponent is not correct. If the sphere is negatively charged to begin with, to add another electron will require positive work. The original 50,000V potential of the sphere would actually be negative. I'm not sure what the intent of the problem is. "Additional electron" hints that it was negatively charged to begin with, but the positive voltage suggests it was positive.
 

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