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 $$Potential\text{ Difference =}\frac{\text{Work Done}}{\text{Amount of Charge Flow}}$$ or
   $$V=\frac{W}{Q}$$

4. 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, $$V_{AB}=\frac{10J}{2C}=5J/C=5V$$

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.

Answer:
Work done, W = 1.25×10¹⁰J
Charge transferred, Q = 200C
Potential difference, V = ?
$$\begin{array}{l}V=\frac{W}{Q}\\ V=\frac{1.25\times {10}^{10}}{200}\\ V=6.25\times {10}^{7}V\end{array}$$

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.