Potential Energy of an Electron in a Battery

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Homework Help Overview

The discussion revolves around the potential energy change of an electron moving between the terminals of a 9V battery. Participants are exploring the implications of charge movement in an electric field and the associated energy changes.

Discussion Character

  • Conceptual clarification, Assumption checking, Mixed

Approaches and Questions Raised

  • Participants are questioning whether the electron gains or loses energy when moving from the positive to the negative terminal. There are discussions about the signs of charge and potential difference, and how they relate to energy changes. Some participants are also addressing assumptions about the nature of the movement and the context of the problem.

Discussion Status

The discussion is active, with various interpretations being explored regarding the movement of the electron and the resulting energy changes. Some participants are providing clarifications on the assumptions made by the original poster, while others are emphasizing the need for clearer problem statements to reduce ambiguity.

Contextual Notes

There are indications of confusion regarding the direction of current flow and the context of the electron's movement, whether internal or external to the battery. The original poster's assumptions and the problem's framing are under scrutiny, highlighting the need for precise definitions in the discussion.

erisedk
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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.
 
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Wouldn't it take work to move an electron away from a positive charge?
 
erisedk said:
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.
 
erisedk said:
An electron moves from the positive to the negative terminal of a battery (9V).

you are starting with an incorrect assumption
try again
 
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.
 
CWatters said:
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 mentionedTo the OP
you need to write a clearer idea of what you are referring to, to stop the ambiguity :smile:D
 
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.
 
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