# A little clarification regarding voltages, and "real" current movement

To my understanding, the voltage supplies the potential, and free electrons are taken from ground? This makes somewhat sense to me, for example if something has a "positive" charge then it will attract negative electrons to it - which works out, however I am unsure if negative charge (relative to one specific point) means more free electrons.

Another question, so mains line provides the potential of 120/240VAC (ignoring AC) and the current does not actually "come" from it, only from ground?

This subject seems to be just taught quickly, it would be very nice to have an understanding that "works" in all aspects I throw at it.

• Well as far as I know it, in AC the electrons shouldn't even be moving. When the voltage changes direction, they go back to where they were, right? Also +1 for the question. Oct 29, 2011 at 17:50
• @AndrejaKo: Yes, except that they also move around randomly. I think the random motion is actually much larger than the drift in one direction caused by your AC voltage. Dec 16, 2011 at 19:40
• @endolith Could be. Dec 16, 2011 at 19:46

To my understanding, the voltage supplies the potential

Voltage is the difference in electric potential between two points. It is analogous to a difference in pressure between two points of a hydraulic circuit.

and free electrons are taken from ground?

Free electrons are everywhere in metal. All matter contains electrons, and in metals, some of those electrons can flow freely. They won't flow until you apply a voltage, though. Applying a voltage causes them to flow, which we call an electric current.

http://amasci.com/miscon/eleca.html#batt

"Ground" is just a label for a point in a circuit. Any point can be considered ground. It's not special, it's just a common reference point for measuring.

Another question, so mains line provides the potential of 120/240VAC (ignoring AC) and the current does not actually "come" from it, only from ground?

Current doesn't "come from" anywhere. Current is a flow of charge, which already exists everywhere.

In electronics, electrons aren't usually important. What's important is flows of charge, waves in charge, etc.