What is the difference between electromotive force and potential difference?

Electromotive force (emf) is the energy supplied per unit charge, while potential difference is the energy used per unit charge.

Electromotive force, often abbreviated as emf, is a concept in physics that refers to the energy provided by a source, such as a battery or generator, per unit charge. It is the total energy supplied to the charge carriers (like electrons) by the source. Emf is measured in volts, the same as potential difference, but they are not the same thing. Emf is the maximum potential difference that can be provided by a source when no current is flowing.

On the other hand, potential difference, also known as voltage, is the work done or energy used per unit charge. It is the energy transferred from electrical energy to other forms of energy when a charge moves between two points in a circuit. The potential difference is the energy used by the charge carriers in the external circuit.

For example, consider a simple circuit with a battery and a bulb. The battery provides the emf, supplying energy to the electrons. As these electrons move through the bulb, they lose energy in the form of light and heat - this energy loss is the potential difference.

In summary, while both emf and potential difference are measured in volts and involve energy and charge, they refer to different aspects of energy in a circuit. Emf is about energy supply, while potential difference is about energy use or transfer.