Question

A charge of `4` `C` is passing through points A and B on a circuit. If the charge's electric potential changes from `45` `J` to `18` `J`, what is the voltage between points A and B?

Answer 1

We have `V=qE` or, better, `Delta V = qDelta E`.

So `Delta V = 4* (18-45)=-108` `V`

The voltage difference between the points is `108` `V`

Explanation:

The negative sign shows that A is at a lower voltage than B, which makes sense because the electric potential energy is lower at B than at A.