**
Electric Potential Energy**

Just like in the gravitational case, the potential falls proportional
to *1/r*. The form of the potential energy *U*
looks the same as the that for the force *F* except for the
different power of *r*.

You include the signs of the charges when you use this formula (unlike the case of calculating the magnitude of a force), so the potential energy is positive if the two charges have the same sign and negative otherwise.

The potential energy of a set of charges,
*q _{a},q_{b},q_{c},... *is
the sum of the potential energies of the pairs.
For instance, if there are 3 charges,
the net potential energy is:

Potential energy is NOT a vector quantity, so the contributions from various charges add up algebraically in this simple way.