Van de Graaff generator energy question

AI Thread Summary
To determine the energy required to add an electron to a Van de Graaff generator charged to 50,000 volts, the calculation involves multiplying the voltage by the charge of the electron, which is -1.6 x 10^-19 C. The initial calculation yields -8 x 10^-18 joules, but this is incorrect due to a misunderstanding of the charge state. If the sphere is negatively charged, adding another electron requires positive work, indicating that the voltage should be considered negative. The discussion highlights confusion regarding the charge state of the sphere and the implications for energy calculations.
Aprilshowers
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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
 
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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?
 
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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