Efficiency of Energy

What is energy efficiency?

• The percentage of energy given out that is useful.

• The percentage of energy given out that is wasted.

• The total energy given to a device or object.

• How many types of energy are given off by a device or object.

What are the units given for efficiency?

• Joules

• No units

• Watts

• Newtons

What is the calculation for efficiency?

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What is the efficiency of this light bulb if it takes 250J of electrical energy and gives off 125J of light energy?

• 25%

• 40%

• 50%

• 75%

What is the efficiency of my dishwasher if I put 100J of electrical energy into it and get 35J of wasted energy?

• 35%

• 50%

• 75%

• 65%

What is the efficiency of my kettle if it takes 125J of electrical energy and uses 75J of thermal energy to boil the water?

• 40%

• 50%

• 60%

• 75%

If my car uses 600J of chemical energy and I measure 100J of sound energy and 150J of heat energy, how efficient is my car?

• 17%

• 42%

• 58%

• 83%

Which of these would be the most efficient?

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Which device shown has an efficiency of 70%?

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Which of these would be the least efficient?

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