Which of the following is necessary for current to flow in a circuit?

For current to flow in a circuit, voltage is essential because it acts as the driving force that pushes electric charges through the conductive path. Voltage, measured in volts, creates an electric potential difference between two points in the circuit. This difference drives the movement of electrons, resulting in current flow.

In a circuit, while resistance might hinder or limit the current (as dictated by Ohm's Law, which states that current is equal to voltage divided by resistance), it is not a requirement for current to flow. Similarly, power, which is the rate of energy transfer, and capacitance, which refers to the ability to store electric charge, do not initiate current flow. Therefore, without the presence of voltage, there would be no potential for current to exist, making it a fundamental requirement in any electrical circuit.