Potential Energy of an Electron in a Battery

[erisedk]

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?

Homework Equations

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.

 

[J Hann]

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

 

[Mister T]

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]

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

you are starting with an incorrect assumption
try again

 

[CWatters]

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]

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

 

[Mister T]

The OP didn't state this, he's just trying to understand the statement he was given and answer a question about it. It makes no difference how the electron gets there. The positive terminal is at a potential of +9 volts relative to the negative terminal. An electron in the latter location has how much potential energy relative to an electron in the former location? That's an equivalent question.