Electron moving from high->low potential,electric potential energy incr?

Discussion in 'MCAT Study Question Q&A' started by coldviva204, 08.22.08.

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1. coldviva204coldviva204 2+ Year Member

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As an electron moves from a high potential to a low potential, its electrical potential energy does it decrease or increase?

Alot of people tell me that it DECREASES in energy, just like gravitational potential acting on an object.

But I thought it INCREASES in energy, because electrons usually move from low potential to high potential. Is there any one here who knows the CORRECT answer to this question? THANKS

3. spyderracing32 5+ Year Member

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I think you're thinking about areas of high potential being areas closest to a positive charge (and thus furthest from the tip of the electrical field line); don't think about it like that. When a test charge is closest to a like charge its potential is going to be at a maximum. As it is accelerated away from the charge its potential is converted to kinetic energy, and will thus be at a minimum when in static contact with an opposite charge.

4. coldviva204coldviva204 2+ Year Member

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So that means electron go from high potential to low potential, it loses energy? It doesn't have anything to do with the positive test charge?

5. Ninjaface 2+ Year Member

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Potential due to an electric field is usually assumed to originate from a positive charge always (field lines go out from positive to negative), so an electron moving to a higher potential (closer to the field line origins) will be losing potential energy. If it is not restrained it will be gaining kinetic energy though. Like spyder says the opposite will hold if it is being moved closer to a like (negative) charge. In that case it will be moving along the direction of the electric field lines.

6. AZFutureDoc 5+ Year Member

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positive charge: high to low potential.
negative charge: low to high potential.

7. andafooAndy 2+ Year Member

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I think a combination of this ^ and what spyder mentioned will answer your question fine.

I think what is confusing is the convention of + and -. The electric field is defined to be the force felt by a test charge (+1). You can visualize this using electric field lines.

Knowing this, you can see how electric field points from a positive center to a negative center (higher to lower potential).

8. andafooAndy 2+ Year Member

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Quick question I wanted to verify...

If you plop an electron down in an electric field.. it WILL feel a force in the opposite direction, right? Does this also mean the force it feels due to a magnetic field will also be in the opposite direction?

I hoping to hear some yeses!

9. spyderracing32 5+ Year Member

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Yea the potentials are designated high and low for positive and negative respectively, but I think what got me through physics so well was really ignoring these conventions in terms of understanding the concept while paying heed to them while taking exams. So many designations in physics are completely arbitrary.

And yes andafoo, you are correct.