How is energy in watt-hours calculated for a device operating at rated power for a given time?

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Prepare for the CWEA Electrical/Instrumentation (E/I) Grade 1 Test. Use flashcards and multiple-choice questions, each with hints and explanations. Get ready for your exam!

Multiple Choice

How is energy in watt-hours calculated for a device operating at rated power for a given time?

Explanation:
Energy used by a device is found by multiplying its power by the time it runs. Power is in watts and time is in hours, so the energy in watt-hours is P × t. For example, a 100 W device running for 2 hours uses 200 Wh (0.2 kWh). The other operations don’t fit the units of energy: adding time to power, dividing power by time, or subtracting time would not yield a valid energy value in watt-hours.

Energy used by a device is found by multiplying its power by the time it runs. Power is in watts and time is in hours, so the energy in watt-hours is P × t. For example, a 100 W device running for 2 hours uses 200 Wh (0.2 kWh). The other operations don’t fit the units of energy: adding time to power, dividing power by time, or subtracting time would not yield a valid energy value in watt-hours.

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