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Energy �and �Power�

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�Energy �vs. �Power�

What’s the difference?

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Definitions

Energy

The ability to do work

(Without energy no work can be done. . .)

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Power

The rate which energy is transformed

(In other words, how FAST you use energy)

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1st Law of Thermodynamics

Energy can never be created or destroyed

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Since we can’t make energy. . . . we have to transform energy from one kind to another

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Remember the transformation examples we talked about in our last lesson?

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Electricity

Light + Heat

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Chemical

Motion + Heat

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Power

Just to review. . .

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Power is how FAST energy is transformed from one kind to another.

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Some Analogies…

If power is the SPEED (rate) we are moving. . .

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Energy is the TOTAL distance we travel

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If a Nike factory makes 1,000 shoes in an hour, how many shoes do we have after 8 hours?

Answer:

1000 shoes/hour x 8 hours = 8000 shoes

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If a Nike factory makes 1,000 shoes in an hour, how many shoes do we have after 8 hours?

Answer:

1000 shoes/hour x 8 hours = 8000 shoes

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In the shoe example. . .

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1. What represented power?

2. What represented energy?

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Don’t Forget Units!

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  • Unit of Power is the Watt (W)
  • 1,000 Watts = 1 kilowatt

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Our electricity company charges us in “kilowatt-hours”

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Example: A 100-Watt Light Bulb

If a 100-Watt light bulb operates for 20 hours. . .�

1. How many Watt-hours � of energy were � transformed into light?�

2. How many kilowatt-hours were � used?

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Example: A 100-Watt Light Bulb

A 100-Watt light bulb operates for 20 hours

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    • How many Watt-hours � of energy were � transformed into light?

Answer: 100 W x 20 hours = 2000 Watt-hours

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2. How many kilowatt-hours?

Answer: 2000 Watt-hours/1000 = 2 kilowatt-hours

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How do I do my “Energy Consumption Worksheet” Homework?

  1. Use your Kill-Watt-Meter (or check appliance label) to find Power required to operate each device
  2. Multiply the power by the number of hours of operation to find total energy consumed
  3. Multiply the hours of operation per day by 30 to find the energy consumed in a month
  4. Multiply the amount of energy consumed by the cost of energy [PROVIDE COST OF ELECTRICITY HERE]

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Special thanks to Deb Frankel who created the original PowerPoint which has simply been adapted