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# Energy - Transfers and Efficiency

This Physics quiz is called 'Energy - Transfers and Efficiency' and it has been written by teachers to help you if you are studying the subject at senior high school. Playing educational quizzes is one of the most efficienct ways to learn if you are in the 11th or 12th grade - aged 16 to 18.

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The principle of conservation of energy states that 'energy can neither be created nor destroyed, only changed from one form into another'. Energy changes make the world work. Plants transfer the light energy from the Sun into chemical energy of food by photosynthesis. Animals, including humans, change the chemical energy of food into heat and kinetic energy. We transfer the chemical energy stored in coal, oil and gas into electrical energy to run our electronic appliances and machines; into kinetic energy to run our vehicles; into heat energy to cook our food and more.

1.
Which formula can be used to calculate the percentage of energy transferred by a device?
Energy Transferred = Useful Energy OutputTotal Energy Input x 100
Energy Transferred = Total Energy InputUseful energy output x 100
Energy Transferred = Useful Energy OutputTotal Energy Input x 10
Energy Transferred = Total Energy InputUseful energy output x 10
This is called the efficiency of an energy transfer
2.
A solar panel is 20% efficient at converting light energy into electricity. If it generates 200 joules of electrical power, how much power is wasted?
500 J
750 J
800 J
1000 J
This is an alternative way for the examiners to check your understanding of efficiency
3.
A wind turbine generates 100 joules of electricity from a gust of wind which has 300 joules of energy. How efficient is the turbine?
10%
33%
50%
66%
Wind turbines are an example of renewable energy
4.
Which formula can be used to calculate the percentage of power transferred by a device?
Power Transferred = Useful Power OutputTotal Power Input x 100
Power Transferred = Total Power InputUseful Power Output x 100
Power Transferred = Useful Power OutputTotal Power Input x 10
Power Transferred = Total Power InputUseful Power Output x 10
More efficient devices waste less energy
5.
What can be done to energy?
It can be transferred
It can be stored
It can be dissipated
All of the above
Not all forms of energy can be stored
6.
Calculate the efficiency of a heater which can convert 700 joules of chemical energy into 175 joules of heat energy.
10%
25%
35%
50%
Remember, efficiency is normally given as a percentage
7.
What cannot be done to energy?
Created or destroyed
Dissipated
Transferred
Stored
It is impossible to create or destroy energy. In a science lesson, you may have watched a balloon being popped - all of the elastic energy within the balloon is transferred into sound, heat and kinetic energy
8.
What happens to wasted energy?
It decomposes into the ground
It becomes hot
No energy is ever wasted
It is transferred into its surroundings
Any energy wasted by a process will always dissipate into its surroundings. Although it is still there, because it is so spread out, it makes it much more difficult to use
9.
During an energy transfer, only part of it may be usefully transferred. What happens to the remainder of the unused energy?
It's wasted
All the energy is all transferred and used successfully
It is converted into carbon
It becomes a gas
In every energy transfer, some energy is wasted
10.
An LED converts around 80% of the energy supplied to it into light. How much energy is converted into light if a total of 50 J is supplied to it?
30 J
40 J
50 J
60 J
LEDs are a much more efficient way of transferring electrical energy into light energy than the conventional filament bulb and fluorescent lamps ~ they last longer too
Author:  Martin Moore