# Voltage

#### meming

Joined Aug 21, 2011
3
Hello, I'm kind of new to electronics, I've been understanding things pretty well but I'm confused about voltage. I know that it is the potential energy difference between 2 points per unit charge, but what determines voltage? If we use gravitational potential energy, the heavier the masses and the farther they are away the more GPE you have, does this mean if I have 2 charges in space the more difference in charge I have and the farther they are away the more PE I have? What if we put 2 charges on 2 sides of a conductor, how would I change the voltage across the conductor? Increasing the difference in charge? How does a conductor change things? Answering any of these questions will help me, thanks.

#### SgtWookie

Joined Jul 17, 2007
22,221
http://en.wikipedia.org/wiki/Voltage

Voltage is simply an electrical pressure difference, or more simply, just pressure.

Pressure by itself doesn't amount to much though. You need to have current flow in order for work to be done; the amount of power expended. Watts (power) = voltage * current.

#### steveb

Joined Jul 3, 2008
2,436
... I know that it is the potential energy difference between 2 points per unit charge, but what determines voltage? If we use gravitational potential energy, the heavier the masses and the farther they are away the more GPE you have, does this mean if I have 2 charges in space the more difference in charge I have and the farther they are away the more PE I have? ...
It's not the distance away that matters. At least not directly. If you have capacitor plates and you have charge on the plates, then separating the plates more (with the connection open) will in fact increase the voltage. However, this can be a little misleading. What really matters is the force encountered as the charges are moved. So, electric field is force per unit charge and voltage is energy per unit charge. Since energy is the integration of force over distance, then voltage is the integration of electric field over distance.

Actually, the same is true for GPE. The dependence on distance at the surface of the earth is a special case, just as the dependence on distance for capacitor plates is a special case. These cases are directly analogous.

So, what determines voltage is the work done as the charges are moved from one point to another, which is the same as with potential energy in a gravitational field.

• meming