electrons and 'work'- what happens

[orange31]

Simplistic question, I understand how electrons come from power source, thru a motor/any device, return via ground to source. Same number of electrons start to finish.
My question is, what is the change in the electrons that reflects the energy consumed to perform the work?

[drkitten]

Simplistic question, I understand how electrons come from power source, thru a motor/any device, return via ground to source. Same number of electrons start to finish.
My question is, what is the change in the electrons that reflects the energy consumed to perform the work?

Reduced voltage (or electromotive force).

[Ziggurat]

drikitten's response is correct, but it may not be quite what you're looking for. One way to get a bit of a more "physical" picture of what's going on is to consider electrons in a metal kind of like a gas with a pressure. Electrons repel each other, so the more electrons you shove into a metal, the higher the "pressure" (corresponding to more negative voltage). Electrons will try to flow away from the higher pressure to lower pressure, just like a gas would, and they can do work (like heating the filiment in a lightbulb) in the process.

This is an imperfect analogy for a number of reasons (in other words, don't look for perfect correspondance), one of which is that the electron density at any one spot isn't the only thing that affects voltage at that spot (in a chunk of metal without any current, the voltage is equal everywhere but any net electron charge will be on the surface only). Another difference is that it's a FANTASTICALLY stiff "gas": the fractional change in electron density needed to make HUGE changes to the voltage are very small. But voltage differences (and the corresponding electric fields) are created by increasing or decreasing the electron density in your conductor, even if by only very tiny amounts. In contrast, ordinary gasses need significant density changes in order to experience significant pressure changes (assuming fixed temperature, of course).

[Madalch]

It's similar to a water wheel. Water flows downstream, turns the wheel and does useful work. What is the change in the water that reflects the work it's done?

[Gord_in_Toronto]

It's similar to a water wheel. Water flows downstream, turns the wheel and does useful work. What is the change in the water that reflects the work it's done?

Lower Potential Energy? ;)

[drkitten]

drikitten's response is correct, but it may not be quite what you're looking for. One way to get a bit of a more "physical" picture of what's going on is to consider electrons in a metal kind of like a gas with a pressure. Electrons repel each other, so the more electrons you shove into a metal, the higher the "pressure" (corresponding to more negative voltage). Electrons will try to flow away from the higher pressure to lower pressure, just like a gas would, and they can do work (like heating the filiment in a lightbulb) in the process.

Thanks. I was trying to find a physical analogy to use but failing to find a way to express it that wasn't "obviously wrong"[tm].

[Madalch]

Lower Potential Energy?
Yep- just like the electrons.

If you have a battery that operates by the flow of electrons from zinc to copper ion, the electrons have a lower potential energy in the orbitals around copper than they do when they're in the orbitals of a zinc atom.

[Soapy Sam]

It's like when you use your credit card to pay a bill.
Credit card does work, gets hot, remaining credit is reduced, spending power goes down.

Hey- it's a metaphor for the "Me Generation"

[orange31]

If you have a battery that operates by the flow of electrons from zinc to copper ion, the electrons have a lower potential energy in the orbitals around copper than they do when they're in the orbitals of a zinc atom.

Aha! thanks!

[wackyvorlon]

Around the turn of the century, it was common to use water as an analogy. One paper by Tesla even refers to currents of "high pressure", which we would today consider voltage. Vacuum tubes in the UK are still referred to as valves.