Distinguish between a potentiometer and a voltmeter.

Hint: The voltmeter is an instrument used to measure the terminal voltage of the circuit. The potentiometer is a device that is used to measure the emf of the circuit. Thus, in basic words, the devices, voltmeter and the potentiometer are used to measure the voltage of the circuit.

Complete step-by-step solution:
The devices, potentiometer and the voltmeter, both are used to measure the voltage. The difference being, the potentiometer reads the emf of the circuit, emf refers to the electromotive force, that is, the voltage through the circuit, whereas, the voltmeter reads the terminal voltage, the terminal voltage refers to the voltage across the terminal of a circuit.
The voltmeter makes use of the current to measure the voltage, the potentiometer doesn’t use the current to measure the emf, as it is an open circuit measurement. The voltmeter is the current controlled device and the potentiometer is the null method device.
\[\therefore \] The voltmeter is an instrument used to measure the terminal voltage of the circuit, whereas, the potentiometer is a device that is used to measure the emf of the circuit. The potential difference in an open circuit is measured by the potentiometer, whereas, the voltmeter in a closed circuit draws the current to measure the terminal voltage.

Note: The emf refers to the electromotive force, that is, the voltage through the circuit, whereas, the terminal voltage refers to the voltage across the terminal of a circuit. The actual value of the voltage of the battery/circuit is measured by the potentiometer and not the voltmeter. The sensitivity of the potentiometer is more than that of the voltmeter.