# A charge of 4 C is passing through points A and B on a circuit. If the charge's electric potential changes from 32 J to 9 J, what is the voltage between points A and B?

Jan 19, 2016

A volt is defined as a joule per coulomb, $V = {E}_{e} / Q$. In this case, $V = \frac{32 - 9}{4} = 5.75 V$

#### Explanation:

A volt is a unit of electric potential. A joule is a measure of electric potential energy. A volt is defined as a joule per coulomb: if 1 coulomb $\left(C\right)$ of charge is moved through a potential difference of 1 volt $\left(v\right)$, its electric potential energy will change by 1 joule $\left(J\right)$.

In this case $4 C$ of charge moved such that its electric potential energy changed by $32 - 9 = 23 J$. We are asked for the potential difference in volts between the two points.

$V = \frac{32 - 9}{4} = 5.75 V$

(Note: The question is phrased imprecisely, since 'electric potential' should be measured in volt and 'electric potential' energy in joule)