Question

A hard rubber rod with an electric potential energy of 5.2 × 10–3 J has a charge of 4.0 µC at the tip. What is the electric potential at the tip?

Answer 1

\[V = \frac{U}{Q}\]potential is potential energy per coulumb.

the charge is giving rise to the potential and the potential energy.

Answer 2

we can think to your system as a capacitor, like this:

now, if I call with U the electrical potential energy, then we can write:
\[\Large U = \frac{1}{2}C{V^2} = \frac{1}{2}QV\]
where C is the capacitance of your capacitor, and V is the requested voltage. So we have:
\[\Large V = \frac{{2U}}{Q} = ...?\]