Students should be able to explain how the power transfer in any circuit device is related to the potential difference across it and the current through it, and to the energy changes over time: power = potential difference × current, P = V I; power = current2 × resistance, P = I2 R (power, P, in watts, W; potential difference, V, in volts, V; current, I, in amperes, A (amp is acceptable for ampere); resistance, R, in ohms, Ω) • Students should be able to recall and apply both equations.