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## Homework Statement

A point charge q

_{1}is held stationary at the origin. A second charge q

_{2}is placed at point a, and the electric potential energy of the pair of charges is + 5.4 x10^-8 J. When the second charge is moved to point b, the electric force on the charge does - 1.9x10^-8 J of work.

A) What is the electric potential energy of the pair of charges when the second charge is at point b?

## Homework Equations

U = kq

_{1}q2/r

W = -ΔU

## The Attempt at a Solution

I'm having a little difficulty understanding the concept of electric potential energy. This is what I think I understand.

A search on Google told me that U = 5.4x10^-8 J is the potential energy of the two charges, but the question seems to suggest to me that this value could be ΔU, how do I know it is not ΔU?

Also, would I be correct in saying that

W = -ΔU

therefore this would mean that:

-1.9x10^-8 J = -ΔU

As such the ΔU = 1.9x10^8 J

Additionally, because the work done is negative does this mean that q

_{2}is being pushed away from q

_{1}as there is work being done on q

_{2}by q

_{1}?

Assuming my thought process has been somewhat accurate so far, would it then be reasonable to say that the electric potential energy has increased and that the electric potential energy of the charges when q

_{2}is at point b would be:

5.4x10^-8J + 1.9x10^-8 J = 7.3x10^-8J

7.3x10^-8 J is the correct answer, but I want to know if my thought process is correct. I'm feeling a bit scatterbrained on this topic.

Any extra input would be appreciated.