Answer:
Voltmeter
Explanation:
A voltmeter is a device which is used to measer potential difference across a load or source in an eletric circuit. It is a high resistence device and is connected in parallel with load or source in a circut . If it is connected across a source in an open circuit , it gives measurement of emf whereas it measures potential difference if it is connected across a load in a close circuit.IT has two terminals they are positive terminal with red colour and negative terminal with black colour.