Take a look at an ordinary light bulb and you will notice that its wattage is indicated. For example, the bulb might read 100 watts, 60 watts, 40 watts, and so on. The wattage marked on a bulb
indicates the amount of electricity that bulb will use in one hour
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For example, a 100-watt bulb will use 100 watt-hours of electricity in 1 hour. Similarly, a 60-watt bulb will use 60 watt-hours of electricity in 1 hour. How many watt-hours of electricity will a 40-watt bulb use in one hour? _________ watt-hours
Will a 15-watt bulb use 30 watt-hours of electricity in 1 hour?__________
Since a 40-watt bulb will use ___ watt-hours of electricity in 1 hour, then the same bulb will use ___ watt-hours of electricity in 2 hours. How many watt-hours of electricity will a 40-watt bulb use in four hours? ___ To answer this question you must multiply the number ___by the number ___. You find that a 40-watt bulb will use 16 0 watt-hours of electricity in four hours.
Answer the following:
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1. A 100-watt bulb will use 100 ______ of electricity in one hour.
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2. Two 100-watt bulbs will use ________ of electricity in one hour.
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3. How many watt-hours of electricity will three 60-watt bulbs use in 1 hour? In 3 hours?
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1 hour_________
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3 hours________
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The average family will use many 100-watt bulbs, many other bulbs of varying wattages, and a number of electrical appliances as well. It is for this reason that the typical home will probably use during one month several thousand watt-hours of electricity.
Because the average home will use several thousand watt-hours of electricity in one month, it is more convenient to measure the amount of electricity in a unit larger than the watt-hour. One kilowatt-hour is equal to 1000 watt-hours.
1 kwhr = 1000 watt-hours
REMEMBER that the kilowatt-hour is larger than the watt-hour.
Two kilowatt-hours equal ___ watt-hours.
500 watt-hours equal ___ of a kilowatt-hour.
How many watt-hours equal 5 kilowatt-hours? ___
If five 200-watt bulbs were used for one hour, they would use a total of 5 times 200 watt-hours or 1000 watt-hours or 1 kilowatt-hour
.
Answer the following:
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1. If each fluorescent tube in the lighting
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fixtures in your classroom is labeled 40
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watts, how many watt-hours of electricity is
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being used in 1 hour? How many kilowatt hours in 1 hour?
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2. How many kilowatt-hours are lights in this classroom are turned on for 8 hours?
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3. In what other ways besides the overhead lighting is electricity used in the classroom?
