Question
Thu May 26, 2011 By: Sachin Gupta

what is a potential difference ? How is it created by a cell in a electric circuit?

Expert Reply
Thu May 26, 2011
The phrase 'potential difference' means the difference in electrical charge between two points in a circuit expressed in volts

Potential at a point is the potential energy possessed by a unit charge placed at the point.
Potrential is different from potential energy. Potential energy per unit charge alone is potential. The unit charge is to be noted. 

Potentials are measured in volts.

The potential difference is the difference in potentials between two points Aand B.

The difference in potentials measured between A and B is also equal to the work to be done on a unit charge to move it from B to A.

electromotive force, or most commonly emf (seldom capitalized), or (occasionally)electromotance is "that which tends to cause current (actual electrons and ions) to flow.

More formally, emf is the external work expended per unit of charge to produce an electric potential difference across two open-circuited terminals. The electric potential difference is created by separating positive and negative charges, thereby generating an electric field. The created electrical potential difference drives current flow if a circuit is attached to the source of emf. When current flows, however, the voltage across the terminals of the source of emf is no longer the open-circuit value, due to voltage drops inside the device due to its internal resistance.

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