Which unit is used to measure energy consumption over time in electrical circuits?

• A. Watt-hours
• B. Amperes (amps)
• C. Volts
• D. Ohms

Answer: (A)

Energy consumption over time is measured in watt-hours. Energy equals power times time, so when you know a device’s power in watts and how long it runs in hours, multiplying them gives energy in watt-hours. For example, a 60-watt bulb running for two hours uses 120 watt-hours (0.12 kilowatt-hours). Kilowatt-hours are commonly used on electric bills because they represent total energy used, not just instantaneous power.

The other units describe different quantities: amperes measure current, volts measure electrical potential, and ohms measure resistance. They tell how the circuit behaves, not how much energy is consumed over a period. One watt-hour equals 3600 joules, linking the practical unit to the SI system.