# A charge of 5 C is passing through points A and B on a circuit. If the charge's electric potential changes from 27 J to 7 J, what is the voltage between points A and B?

Mar 10, 2016

$4 V$

#### Explanation:

We use the definition of electrical potential, or Voltage as given by

$V = \frac{\Delta E}{Q}$

where $V$ is the voltage change between two locations, $\Delta E$ is the change in potential energy and $Q$ is the charge that is moving. The change in potential energy in going from A to B (final state being at point B):

$\Delta E = 7 J - 27 J = - 20 J$

Then the voltage at B with respect to A is

${V}_{B} = \frac{- 20 J}{5 C} = - 4 V$

Therefore, the voltage at point B is $4 V$ lower than the voltage at point A.