The potential difference measured in volts is the amount of work to move a charge from one point to another along a circuit. What is this quantity called?

• A. Voltage
• B. Current
• C. Resistance
• D. Capacitance

Answer: (A)

The key idea here is that voltage is the energy per unit charge required to move a charge between two points. It’s defined as V = W/q, so one volt means one joule of work is needed (or gained) for each coulomb of charge moved. This is why the quantity measured in volts is the potential difference between two points, the driving "push" that moves charges in a circuit.

Current, by contrast, is how much charge flows per unit time—the rate of flow, not the energy per charge. Resistance is how hard it is for current to flow, i.e., the ratio of voltage to current (R = V/I). Capacitance describes how much charge a component can store per unit voltage (Q = C V).