# Potential and Potential Difference

### Potential and Potential Difference

1. The electric potential V at a point in an electric field is the work done to bring a unit ( 1 Coulomb) positive charge from infinity to the point.
2. The potential difference (p.d.) between two points is defined as the work done in moving 1 Coulomb of positive charge from 1 point in an electric field to another point.
3. In mathematics or
$V= W Q$
1. Example, in the diagram above, if the work done to move a charge of 2C from point A to point  is 10J, the potential difference between A and B, $V AB = 10J 2C =5J/C=5V$

Example:
During an occasion of lightning, 200C of charge was transferred from the cloud to the surface of the earth and 1.25×1010J of energy was produced. Find the potential difference between the cloud and the surface of the earth.

Work done, W = 1.25×1010J
Charge transferred, Q = 200C
Potential difference, V = ?
$V= W Q V= 1.25× 10 10 200 V=6.25× 10 7 V$

### Arrangement of Ammeter

To use the ammeter in the measurement of an electric current, the ammeter must be connected in series to the circuit.

### Arrangement of Voltmeter

To use the voltmeter in the measurement of potential difference across an object, the voltmeter must be connected in parallel to the circuit.