# Potential energy in a battery

## Homework Statement

An electron moves from the positive to the negative terminal of a battery (9V). How much potential energy did it gain or lose?

## The Attempt at a Solution

Solving for the amount is basic. That's just qV = 14.4 * 10^-19 J
I'm not sure whether it will gain the energy or lose it.
I believe that since the positive terminal is at a higher potential, a positive charge would lose energy, and therefore, the electron will gain energy. But the answer at the back says that it would lose energy. I'm not sure what's wrong.

Wouldn't it take work to move an electron away from a positive charge?

Mister T
Gold Member
That's just qV

The more general relation is ##\Delta U=q \ \Delta V## where ##\Delta V## is the change in potential. If ##q## and ##\Delta V## have different signs, then ##\Delta U## is negative. If they have the same sign then ##\Delta U## is positive.

davenn
Gold Member
An electron moves from the positive to the negative terminal of a battery (9V).

you are starting with an incorrect assumption
try again

CWatters
Homework Helper
Gold Member
No he isn't. The problem statement ask what happens if an electron moves from positive to negative. That occurs when a battery is being charged.

davenn
Gold Member
No he isn't. The problem statement ask what happens if an electron moves from positive to negative.

we shouldn't nitpick
he didn't say what if ... he stated it as a fact

An electron moves from the positive to the negative terminal of a battery

this isn't likely to happen as it goes against the current flow

Noting that he hasn't stated if this is internal or external to the battery ... the norm being an external reference
battery charging also wasn't mentioned

To the OP
you need to write a clearer idea of what you are referring to, to stop the ambiguity

D

Mister T