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

Answer:

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.