A charge of 15 C is passing through points A and B on a circuit. If the charge's electric potential changes from 25 J to 12 J, what is the voltage between points A and B?

1 Answer
Jan 23, 2017

The voltage would have dropped by 0.867 V to cause this decrease in potential energy.

Explanation:

We use the definition of electric potential to do this one:

"potential difference"=("work done")/("quantity of charge")

or V=W/q

The "work done" in this case refers to the change in electrical potential energy of the charge.

Note: In the problem, it states "the electric potential changes from 25J to 12J".
This should read "the electric potential energy changes from 25J to 12J".
The "electric potential" is another name for "voltage difference", and is measured in joules per coulomb (which is the same as volts).

Getting back to the question:

The voltage then must be

V = (13J)/(15C)=0.867 "volts"

One last decision to make - since this was a positive charge, and the potential energy decreased, it must have moved through a reduction in potential. By definition, a positive charge increases in potential energy when it moves through an increase in potential.