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Power Consumption. How do we measure the electricity we use? This presentation came from Virginia Tech and has not been edited by the Georgia Curriculum Office. Performance Objectives. Students will list and describe terms used to measure electricity. Enabling Objectives.
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Power Consumption How do we measure the electricity we use? This presentation came from Virginia Tech and has not been edited by the Georgia Curriculum Office.
Performance Objectives • Students will list and describe terms used to measure electricity.
Enabling Objectives • Given the instruction in class, and problems for practice, the student will be able to calculate watt-hours and kilowatt-hours used by an electrical appliance with 80 % accuracy minimum.
Interest approach • Whenever we purchase an electrical appliance, especially a heavy duty one, do we ever consider how it may effect our electric bill. Even though we spent a considerable amount of money on the purchase, it still costs us to operate the new appliance.
What unit do we purchase electricity in? • The electric company bills customers based on the kilo-watt hours of electricity used each month. • Definition • A kilowatt-hour is equal to 1000 watt-hours of electricity.
Watt-hours • In order to understand kilo-watt hours, we must first learn what watt-hours are. • Step 1– Determine or calculate the watts used by an appliance. This can be done by reading the nameplate or by using the formula W = V x A.
Watt-Hours • Step 2—After determining the watts used, estimate the number of hours the appliance will be used per month. • Step 3—Multiply the watts times the hours of operation to determine watt-hours.
Calculations • A 1 horsepower motor uses 1000 watts of electricity for 10 hours. How many watt-hours were consumed by the motor? • 1000 watts x 10 hours = 10,000 watt-hours
Calculations • To convert the previous answer to kilowatt hours, simply divide your answer by 1000. • 1 kilowatt-hour is equal to 1000 watt-hours • 10,000 watt-hours / 1000 = 10 kilowatt-hours
Perform the following • How many kilowatt-hours would a 100 watt light bulb use in 5 hours?
Answer • 100 watt bulb x 5 hours = 500watt-hours • 500 watt-hours/ 1000 = .5 kilowatt-hours
Perform the following: • How many kilowatt-hours of electricity would a 120 watt mixer use in 15 minutes of operation?
Answer • 15 minutes = ¼ hour • 120 watts x ¼ hour = 30 watt-hours • 30 watt-hours/1000 = .030 kilowatt-hours
Summary • Although we may calculate watt-hours for a piece of equipment or appliance, these are such small units that we must convert them into the kilowatt-hour unit used by the power company in our particular area.