Alberta Grade 9 Science PAT Practice Test

Power in a circuit describes how fast electrical energy is being moved or converted. It’s not about how much energy is stored at a moment, nor about the number of electrons alone, nor about the speed of light. Power tells you the energy per unit time flowing through or delivered to a component. In practical terms, higher voltage or higher current means more energy is transferred every second, which is why power can be calculated as P = VI. For a resistor, power can also be written as P = I^2R or P = V^2/R, showing how both the flow of charge and the ability of the circuit to push that charge (voltage) determine how much energy is being used per second.