Final answer:
A 3-watt alarm clock uses 26.28 kilowatt-hours of electricity if left on for 1 year, calculated by multiplying its power rating in kilowatts (0.003 kW) by the total hours in a year (8,760).
Step-by-step explanation:
To calculate the number of kilowatt-hours of electricity used by an alarm clock left on for 1 year, we first need to know the power rating of the clock, which is typically in the range of 1 to 5 watts. For this calculation, let's assume an alarm clock has a power rating of 3 watts, which is equivalent to 0.003 kilowatts. Since there are 8,760 hours in a year (24 hours per day × 365 days per year), we can multiply the power rating (in kilowatts) by the number of hours the clock is operational to find the total energy consumption in kilowatt-hours (kWh).
The calculation is as follows:
- Energy (kWh) = Power (kW) × Time (hours)
- Energy (kWh) = 0.003 kW × 8,760 hours
- Energy (kWh) = 26.28 kWh
Therefore, a 3-watt alarm clock uses 26.28 kWh of electricity if it is left on continuously for one year.