Energy efficiency

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?

• 30J

• 40J

• 50J

• 60J

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?

• 500J

• 750J

• 800J

• 1000J

Which formula can be used to calculate the percentage of power transferred by a device?

• Power Transferred = Useful Power Output⁄Total Power Input x 100

• Power Transferred = Total Power Input⁄Useful Power Output x 100

• Power Transferred = Useful Power Output⁄Total Power Input x 10

• Power Transferred = Total Power Input⁄Useful Power Output x 10

Tags

NGSS.HS-PS3-3

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%

Tags

NGSS.MS-PS3-5

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 is wasted as a gas

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

What happens to wasted energy?

• It decomposes into the ground

• It becomes hot

• No energy is ever wasted

• It is transferred into the surroundings

Tags

NGSS.MS-PS3-5

What can be done to energy?

• It can be transferred

• It can be stored

• It can be dissipated

• All of the above

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

What CANNOT be done to energy?

• Created or destroyed

• dissipated

• stored

• transferred

Tags

NGSS.MS-PS3-5

Calculate the efficiency of a heater which can convert 700 joules of chemical energy into 175 joules of heat energy.

• 10%

• 25%

• 35%

• 50%