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Name: Hannah
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Age: 12
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Date: 1999 

A volt is the measure of PD. Does PD stand for Power Density? If not, what does it stand for?

Potential difference.

Dr. Ali Khounsary
Advanced Photon Source
Argonne National Laboratory
Argonne, IL 60439

A volt is the measure of the Potential Difference (PD) between two points. The electric potential is the amount of energy per each Coulomb of charge, measured in J/C.

A Coulomb of charge is a large number of charges: 6.25 * 10^18 charges. There is historical reasons for this number, but it works well. You may ask, why the charge of a single electron is not used? When we buy a drink, we usually buy it in a one or two liter bottle, not by the molecule. Similarly, we look at charge by the coulomb and not the individual charge.

Bodies can have different amounts of charge concentrations on them. They are said to be at different potentials, or to have a potential difference between them. When these bodies are connected by a conductor, charges flow from one to the other until both bodies have the same concentration of charge. Potential differences are measured in J/C which is also called a volt.

Nathan A. Unterman

(electrical) potential difference.

Tim Mooney

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