A watt-hour is a unit used to measure energy.

A watt-hour is a unit used to measure energy.

• A. Voltage
• B. Current
• C. Power
• D. Energy

Answer: (D)

A watt-hour expresses energy, because energy equals power multiplied by time. Power, measured in watts, tells how fast energy is being used. Time is in hours, so multiplying them gives energy in watt-hours. If something uses 1 watt for 1 hour, that’s 1 watt-hour of energy. Voltage and current aren’t energy themselves—they describe electrical potential and the rate of charge flow, and while they determine power (voltage times current), they don’t by themselves quantify total energy. Energy is typically in joules in the SI system, but for practical electricity usage we use watt-hours (or kilowatt-hours) to represent the total energy consumed over a period. That’s why this statement is correct.

A watt-hour expresses energy, because energy equals power multiplied by time. Power, measured in watts, tells how fast energy is being used. Time is in hours, so multiplying them gives energy in watt-hours. If something uses 1 watt for 1 hour, that’s 1 watt-hour of energy. Voltage and current aren’t energy themselves—they describe electrical potential and the rate of charge flow, and while they determine power (voltage times current), they don’t by themselves quantify total energy. Energy is typically in joules in the SI system, but for practical electricity usage we use watt-hours (or kilowatt-hours) to represent the total energy consumed over a period. That’s why this statement is correct.