______ is the work done in moving a unit charge between two points in an electric circuit.

In an electric circuit, the potential difference (voltage) is defined as the amount of work done in moving a unit positive charge from one point to another. It is the driving force that pushes electric charges through a conductor. The unit of potential difference is the volt (V), named after the Italian physicist Alessandro Volta. One volt is equivalent to one joule per coulomb (1 V = 1 J/C).

Mathematically, potential difference (V) is given by:
V = W / Q,
where W is the work done (in joules) and Q is the charge moved (in coulombs).

When an electric charge moves through a conductor, energy is required to overcome the resistance of the material. This energy is supplied by the power source (like a battery or generator) and manifests as a potential difference between two points in the circuit.

For example, when a 9V battery is connected to a circuit, it means the battery does 9 joules of work to move 1 coulomb of charge from its negative terminal to the positive terminal.

Potential difference is a fundamental concept in electricity and electronics, as it determines how much energy is available to move charges and perform electrical work—such as lighting a bulb or running a motor. Without a potential difference, electric current cannot flow.

In practical terms, potential difference is measured using a voltmeter, which is always connected in parallel to the component across which the voltage is being measured.

In summary, potential difference represents the energy per unit charge required to move charges between two points, and it plays a vital role in the operation of all electrical devices and circuits.