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 08-22-2008, 05:16 PM #1 coldviva204     Status: Pre-Dental Join Date: Jul 2008 Posts: 16 Electron moving from high->low potential,electric potential energy incr? SDN Members don't see this ad. (About Ads) 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
 08-22-2008, 06:07 PM #2 Senior Member     Status: Medical Student Join Date: Jun 2008 Posts: 374 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.
08-23-2008, 03:22 PM   #3
coldviva204

Status: Pre-Dental
Join Date: Jul 2008
Posts: 16

Quote:
 Originally Posted by spyderracing32 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.

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?

 08-23-2008, 03:33 PM #4 Member   Status: Pre-Medical MDApps: View Profile Join Date: Aug 2008 Location: Yukon, Canada Posts: 67 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.
 08-23-2008, 04:20 PM #5 Senior Member     Status: Pre-Medical Join Date: May 2008 Posts: 778 positive charge: high to low potential. negative charge: low to high potential.
08-23-2008, 04:46 PM   #6
Andy

Join Date: May 2008
Location: Earth
Posts: 111

Quote:
 Originally Posted by AZFutureDoc positive charge: high to low potential. negative charge: low to high potential.
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).

 08-23-2008, 10:36 PM #7 Andy     Status: MD/PhD Student Join Date: May 2008 Location: Earth Posts: 111 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!
 08-24-2008, 01:21 PM #8 Senior Member     Status: Medical Student Join Date: Jun 2008 Posts: 374 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.

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