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P1: Quiz 9
P1: Quiz 9
1) What is the law of conservation of energy?
2) What is the usual wasted energy store that energy is transferred to?
3) Write down either of the equations for energy efficiency. One of the equations is to do with power and the other is to do with energy. You do not need to give the units for the equations.
4) Will a more efficient device have a value for energy efficiency closer to 0% or closer to 100%?
5) 40,000 joules of energy is transferred to an electric mixer that is being used to make a cake. 32,000 joules of energy is transferred usefully. Calculate the efficiency of the electric mixer. Give your answer as a percentage.
6) A 200-watt vacuum cleaner has a useful power output of 130-watts. Calculate the energy efficiency of the vacuum cleaner. Give your answer as a percentage.
7) 180 joules of energy is transferred to a light bulb. The light bulb transfers 43 joules usefully. Calculate the efficiency of the light bulb. Give your answer as a percentage and to the nearest integer.
8) 80 kilojoules of energy are transferred to a coffee machine. 14 kilojoules were transferred to energy stores that are not useful.
a) Calculate the amount of energy that was transferred to useful energy stores.
b) Calculate the efficiency of the coffee machine. Give your answer as a percentage to the nearest integer.
9) A device has an efficiency of 70% and a total power input of 90-watts. Calculate the useful power-output.
10) A device has an efficiency of 28% and a total energy input of 37,000 joules.
a) Calculate the amount of energy that is transferred to useful energy stores.
b) Calculate the amount of energy that is transferred to wasted energy stores.
11) A device has an efficiency of 75%. The device transfers 90 kilojoules to useful energy stores. Calculate the total energy input.
12) A device has an efficiency of 45%. The device has a useful power output of 36-watts. Calculate the total power input of the device.
2) What is the usual wasted energy store that energy is transferred to?
3) Write down either of the equations for energy efficiency. One of the equations is to do with power and the other is to do with energy. You do not need to give the units for the equations.
4) Will a more efficient device have a value for energy efficiency closer to 0% or closer to 100%?
5) 40,000 joules of energy is transferred to an electric mixer that is being used to make a cake. 32,000 joules of energy is transferred usefully. Calculate the efficiency of the electric mixer. Give your answer as a percentage.
6) A 200-watt vacuum cleaner has a useful power output of 130-watts. Calculate the energy efficiency of the vacuum cleaner. Give your answer as a percentage.
7) 180 joules of energy is transferred to a light bulb. The light bulb transfers 43 joules usefully. Calculate the efficiency of the light bulb. Give your answer as a percentage and to the nearest integer.
8) 80 kilojoules of energy are transferred to a coffee machine. 14 kilojoules were transferred to energy stores that are not useful.
a) Calculate the amount of energy that was transferred to useful energy stores.
b) Calculate the efficiency of the coffee machine. Give your answer as a percentage to the nearest integer.
9) A device has an efficiency of 70% and a total power input of 90-watts. Calculate the useful power-output.
10) A device has an efficiency of 28% and a total energy input of 37,000 joules.
a) Calculate the amount of energy that is transferred to useful energy stores.
b) Calculate the amount of energy that is transferred to wasted energy stores.
11) A device has an efficiency of 75%. The device transfers 90 kilojoules to useful energy stores. Calculate the total energy input.
12) A device has an efficiency of 45%. The device has a useful power output of 36-watts. Calculate the total power input of the device.