Energy Consumption
Power is associated with the flow of electricity in a circuit. Your electric company determines your monthly electric bill based on how much electricity you have used. Electrical power is measured in watts (W).
When p watts are used for t hours, the amount of energy measured in watt-hours is represented by the expression p.t ("p dot t"). The electric meter for your home measures the amount of electricity you use in units called kilowatt-hours (kW.h).
A kilowatt is 1000 watts.
To find the number of kilowatt-hours an appliance uses, use the expression p.t to determine the number of watt-hours used and then divide by 1000. You can get an idea of what 1 kW.h of electricity is by thinking of a 100-watt light bulb. To use 1 kW.h of electricity, you need to burn the 100-watt light bulb for 10 hours.
Example
An air conditioner uses 1330 watts for 6 hours. How many kilowatt-hours does it use?
Exercises
1. An iron using 1008 watts is plugged in for 2 hours. How many kilowatt-hours are used?
2. A clothes dryer uses 4856 watts. How many kilowatt-hours are used if it runs for 10 hours?
By : Mr. Danielz
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