Voltmeter is the device that is used to measure the potential difference across the battery.
What are the usage of voltmeter?
Usage of Voltmeter
Voltmeter is an instrument that measures voltages of both direct and alternating electric current. On a scale of voltmeter usually graduated in volts, millivolts (0.001 volt), or kilovolts (1,000 volts).
Voltmeter is connected in parallel form. It has a high resistance so that it takes negligible current from the circuit so we can conclude that Voltmeter is the device that is used to measure the potential difference across the battery.