Selling power

kilowatt-hour

1kilowatt = 1000 watts
A kilowatt-hour represents the amount of energy (in kilowatts) used every hour.

Power companies sell electricity in kilowatt hours. They will charge you for every kilowatt you use every hour. Take a 100 watt light globe the is left on for 30 minutes. If the power company charges 10c per kilowatt hour how much will it cost?

 

 

Step 1 Convert all units to kilowatts and hours.
100 watts = 0.1 kilowatts
30 minutes = 0.5 hours.

Step 2 Find the kilowatt-hours, multiply the kilowatts by the time.
kilowatt hours = 0.1 X 0.5 = 0.05 kilowatt-hours.

Step 3 multiply kilowatt-hours by the cost per kilowatt-hour.
cost = 0.1 X 0.05 = $ 0.005
The cost is half a cent.

1) A 50 watt hair dryer is used for 50 minutes. The power company charges 20c per kilowatt-hour. How much does it cost to operate the hairdryer?

2) A 1200 watt drill is used by a tradesman for 4.5 hours. In this area the power company charges 30c per kilowatt-hour. How much will it cost to operate the drill?
The elastic band provides the tension to automatically close the gate. Metal contacts that complete the circuit and cause the light to glow when the gate is shut The light indicating if the gate is open or closed An electromagnet that activates the lock The bolt that is lifted through a scre eye by the electromagnet The gate
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