The instrument used to determine potential difference in an electrical circuit is the:

The instrument utilized for measuring potential difference, or voltage, in an electrical circuit is the voltmeter. This device is specifically designed to measure the electrical potential energy per unit charge between two points in a circuit, helping technicians and engineers understand voltage levels that can affect circuit performance and safety.

Voltmeters are connected in parallel with the component whose voltage is being measured, allowing them to capture the voltage drop across that component accurately. Their design typically includes high internal resistance to ensure that they do not significantly alter the circuit they are measuring.

In contrast, other instruments like ohmmeters are used to measure resistance, ammeters measure current flowing through a circuit, and potentiometers are utilized for various purposes, including the comparison of voltages or for adjusting resistance in a circuit. Each of these tools plays an important role in electrical work but serves a different function than measuring potential difference.