Potential energy in a battery

  • Thread starter erisedk
  • Start date
  • #1
374
7

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.
 

Answers and Replies

  • #2
264
26
Wouldn't it take work to move an electron away from a positive charge?
 
  • #3
Mister T
Science Advisor
Gold Member
2,663
893
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.
 
  • #4
davenn
Science Advisor
Gold Member
9,511
8,525
An electron moves from the positive to the negative terminal of a battery (9V).

you are starting with an incorrect assumption
try again
 
  • #5
CWatters
Science Advisor
Homework Helper
Gold Member
10,533
2,298
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.
 
  • #6
davenn
Science Advisor
Gold Member
9,511
8,525
No he isn't. The problem statement ask what happens if an electron moves from positive to negative.

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

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 :smile:





D
 
  • #7
Mister T
Science Advisor
Gold Member
2,663
893
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.
 
  • Like
Likes CWatters and erisedk

Related Threads on Potential energy in a battery

  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
1
Views
931
  • Last Post
Replies
7
Views
8K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
4
Views
2K
Replies
5
Views
4K
Replies
2
Views
3K
Replies
8
Views
2K
Replies
6
Views
2K
Top