- For flow of charges in a conducting metallic wire, the electrons move only if there is a difference of electric pressure – called the potential difference – along the conductor.
- This difference of electric potential may be produced by a battery, consisting of one or more electric cells.
- The chemical action within a cell generates the potential difference across the terminals of the cell, even when no current is drawn from it.
- When the cell is connected to a conducting circuit element, the potential difference sets the charges in motion in the conductor and produces an electric current.
- Potential difference (V) between two points = Work done (W)/Charge (Q)
- V = W/Q
- The SI unit of electric potential difference is volt (V), named after Alessandro Volta (1745 –1827), an Italian physicist.
- One volt is the potential difference between two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.
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The potential difference is measured by means of an instrument called the voltmeter. The voltmeter is always connected in parallel across the points between which the potential difference is to be measured.
