Which quantity is the energy that drives the current between two points in a circuit?

• A. Potential difference
• B. Current
• C. Electromotive force
• D. Electric field

Answer: (A)

The energy that moves charges between two points in a circuit is provided by the potential difference (voltage) between those points. This is the energy available to a unit charge as it goes from one point to the other. As charges travel, the electric field established by that potential difference does work on them, giving them energy along the path. The amount of energy per unit charge is exactly the potential difference, so the total energy transferred to a charge q moving between the points is W = V × q. This explains why a larger potential difference produces more current for a given resistance: I = V/R. The electromotive force refers to the energy per unit charge supplied by a source to push charges around the circuit, not the energy difference between two arbitrary points. The current is the flow of charges, while the electric field is what causes that flow.