Electric potential can be defined as the work done in moving a unit positive charge from one point to another. The electric potential between two points is known as the potential difference.
It can be defined as the product of the current through the circuit and the resistance in it, , where is the current and is the resistance.
An instrument that is used to measure the potential difference between two points in an electric circuit is known as a voltmeter or voltage meter.
The voltmeter is connected in a circuit in parallel to measure the voltage in the circuit.
A voltmeter has a very high resistance value. Therefore, it is connected in parallel.
The circuit diagram of a voltmeter is given below, where the voltage is measured between the points and , is the resistance, is the current flowing through the circuit and is the galvanometer used to detect the presence of the current in the circuit.
Hence, the potential difference is measured using a voltmeter.