The measure of energy consumed by a circuit is called __________.

• A. power
• B. energy
• C. voltage
• D. current

Answer: (A)

Energy is the total amount of work or heat produced by a circuit over a period of time. Power, on the other hand, is the rate at which that energy is used—how fast the circuit consumes energy—measured in watts. The energy consumed is what you’d read on an energy bill or in a calculation of total usage, and it’s expressed in joules or kilowatt-hours. Remember that energy equals power times time (E = P × t). For example, a device that uses 200 W for 3 hours consumes 600 watt-hours (0.6 kWh) of energy. Voltage describes the potential difference that pushes charges, and current is the rate of charge flow; neither alone measures the total energy used.