# Still confused about electric potential difference *read first*

1. Jul 5, 2009

### user111_23

I understand what voltage is in the context of electrostatics, but the definition of circuits seems foggy to me.

The common definition I see is something like "voltage is the amount of work per unit charge to be done on a charge moving from A to B". However, this is usually in the context of electrostatics, not circuits. What about the definition for circuits? Please don't give me the water analogy because I have heard it far too much.

Also, I was reading this part of an article about voltage:

"If I grab electrons away from a wire, that wire will have excess protons left behind. If I place those electrons into another wire, then my two wires have oppositely-imbalanced charge. They have a voltage between them too, and a static-electric field extends across the space between them. This field is the voltage."

Does this mean that voltage is an electric field between an imbalance of charges?
If so, why is it called a potential difference?

Here is the source (Warning: it's a very long article):

http://amasci.com/elect/vwatt1.html

Last edited: Jul 5, 2009
2. Jul 5, 2009

### diazona

Water analogy? Actually never mind, maybe I don't want to know... anyway voltage is defined in exactly the same way for circuits. When a current runs through a section of wire, there are electrons moving through that wire, and it takes work to move those electrons. The amount of work per unit charge (of moving electrons) is the voltage, a.k.a. potential difference, along the wire.

Voltage is not an electric field, but it is associated with an electric field. That is, whenever there is an electric field, there will be a change in voltage, and vice-versa. The reason is that if you want to move charges against the electric field, it takes work to do so. The amount of work it takes per unit charge is the voltage, a.k.a. potential difference.

3. Jul 5, 2009

### Phrak

An constant electric field loops around a region of constantly changing magnetic field. What is the voltage at a point A on the loop compared to a the point A on the loop?