# Potential energy question

1. Oct 16, 2008

### jaejoon89

I'm trying to figure out the following question

Which of the following is false?

1) The total work for a a collection of discreet charges is the system's electrostatic potential energy
2) The potential energy for a pair of bodies with positive charges is positive
3) The potential energy for a pair of bodies with opposite charges is positive
4) The potential energy for a pair of bodies with opposite charges is positive
5) The potential energy for a pair of bodies with negative charges is negative

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I know Vtot = V1 + V2 + ... and V = kq/r
so 2) and 5) seem to be true
For 1) W = - delta U so it's not exactly wrong (since the magnitudes are the same) but I don't think it can be considered right either
I'm not sure about 2) or 3)...

2. Oct 16, 2008

### alphysicist

Hi jaejoon89,

That is the formula for potential, not potential energy. What is the formula for the potential energy of two point charges? Do you see how that will change your answers?