Which of the following best defines voltage in an electrical circuit?

Voltage in an electrical circuit is defined as the electric potential energy per unit charge. This concept reflects the ability of an electric field to do work on charged particles, thereby causing them to move through the circuit. Voltage, often measured in volts, quantifies the difference in electric potential energy between two points.

In practical terms, voltage is what pushes electric current through a circuit, and understanding it is crucial for evaluating how circuits operate. For instance, if a circuit has a higher voltage, there is greater potential energy available to push more charge through a given resistance, resulting in increased current flow. This relationship is foundational in electrical engineering and physics, as it connects directly to Ohm's Law and concepts of energy transfer in electrical systems.

The other definitions provided do not accurately capture the essence of voltage. The flow of electric current pertains to the movement of charge carriers and is a function of voltage and resistance, while resistance itself refers to the opposition within a conductor to the flow of current. Power, on the other hand, relates to the rate at which energy is used or transferred in a circuit, which is governed by both voltage and current. Thus, the correct answer comprehensively describes the role of voltage in an electrical context.