Some students investigate the efficiency of electric motors - Edexcel - GCSE Physics - Question 2 - 2013 - Paper 1
Question 2
Some students investigate the efficiency of electric motors.
(a) (i) The students find that one electric motor has an efficiency of 60%. Explain in terms of energy ... show full transcript
Worked Solution & Example Answer:Some students investigate the efficiency of electric motors - Edexcel - GCSE Physics - Question 2 - 2013 - Paper 1
Step 1
Explain in terms of energy what is meant by an efficiency of 60%.
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Answer
An efficiency of 60% means that 60% of the total electrical energy supplied to the motor is converted into useful energy, typically kinetic energy. Therefore, this indicates that 40% of the energy is not used effectively and is lost, often as heat or waste energy.
Step 2
The power of a motor is the rate at which it transfers
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Answer
B energy
Step 3
Calculate the energy supplied to the motor.
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To find the energy supplied to the motor, we use the formula:
extEnergy=extPowerimesextTime
Given that the power rating of the motor is 20 W and the time is 15 s:
extEnergy=20extWimes15exts=300extJ
Therefore, the energy supplied to the motor is 300 J.
Step 4
Calculate the efficiency of this motor.
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The efficiency can be calculated using the formula:
