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.
(i) The students find that one electric motor has an efficiency of 60%.
Explain in terms of energy what... 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
Efficiency refers to how effectively a motor converts electrical energy into useful output energy. An efficiency of 60% means that 60% of the electrical energy input is converted into useful work (kinetic energy), while 40% is lost as waste energy, often as heat. Therefore, if a motor uses 100 J of electrical energy, it will produce 60 J of useful energy.
Step 2
Complete the sentence by putting a cross (X) in the box next to your answer.
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Answer
B energy
Step 3
Calculate the energy supplied to the motor.
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Answer
The energy supplied to the motor can be calculated as follows:
Energy = Power × Time
For the first motor:
Power = 20 W
Time = 15 s
Therefore,
Energy supplied = 20 W × 15 s = 300 J.
Step 4
Calculate the efficiency of this motor.
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Answer
The efficiency of the second motor can be calculated using the formula:
Efficiency (
η
) = (Useful Output Power / Input Power) × 100%
In this case:
Useful Output Power = 18 W
Input Power = 24 W
Thus,
η = (18 W / 24 W) × 100% = 75%.
Step 5
Complete the following sentence by putting a cross (X) in the box next to your answer.
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