# The physics of voltage

Discussion in 'General Electronics Chat' started by jaydnul, Sep 10, 2015.

1. ### jaydnul Thread Starter Member

Apr 2, 2015
132
1
A generator creates an emf in a loop by rotating in a magnetic field which serves as a sudo-electric field through the wire and gives the electrons a reason to move.

My question is how the electrons in the part of the wire that isn't submerged in the magnetic field get moving. They aren't simply pushed along by their neighboring electrons who are submerged in the field, so how does the generator propagate an electric field through the whole wire and not just the part that's in the magnetic field?

2. ### crutschow Expert

Mar 14, 2008
16,227
4,339
But they are pushed along by their neighbors. Why do you think they are not?
Electrons repel one another so as one starts to move, it gets closer to it's neighbor which increases the repulsion between the two, so the neighbor is pushed along, continuing down the line electron-by-electron to the end of the wire (this travels down the wire at about the speed of light).

3. ### ericgibbs AAC Fanatic!

Jan 29, 2010
3,246
566
As already pointed out, the repulsion effect between electrons propagates along the wire close to the speed of light, but the actual physical drift of the electrons along the wire is slow, a few centimetres/second.

Hypatia's Protege likes this.
4. ### crutschow Expert

Mar 14, 2008
16,227
4,339
It's actually slower than that, typically a few centimeters/minute (for example a Wikipedia calculations gave a value of 0.00028 m/s or 1.68 cm/minute for a current of 3A going through a 1 mm [18AWG] diameter wire.)
This indicates the rather amazing number of free electrons there are in a small piece of copper.

cmartinez and Hypatia's Protege like this.
5. ### Hypatia's Protege Distinguished Member

Mar 1, 2015
3,070
1,819
Thank you. gentlemen! -- It is truly refreshing to encounter folk who apprehend the nature of conduction!

Most sincerely
HP

nsaspook likes this.
6. ### jaydnul Thread Starter Member

Apr 2, 2015
132
1
Cool.

The only reason I asked is because I read somewhere that the electrons in the metal lattice don't interact with each other. I soon figured out that was only said because of their attraction to the neighboring protons in the metal; clearly they would repel if the charge density changed. Thanks for the help!