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Some students investigate the efficiency of electric motors - Edexcel - GCSE Physics - Question 2 - 2013 - Paper 1

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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

An efficiency of 60% means that 60% of the total energy supplied to the motor is converted into useful energy. This implies that for every 100 units of input energy, 60 units are used for useful work, while the remaining 40 units are wasted, often as heat.

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 can be calculated using the power and time. The formula is:

Energy=PowerimesTimeEnergy = Power imes Time

Substituting the values:

Energy=20extWimes15exts=300extJEnergy = 20 ext{ W} imes 15 ext{ s} = 300 ext{ J}

Therefore, the energy supplied to the motor is 300 J.

Step 4

Calculate the efficiency of this motor.

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Efficiency can be calculated using the formula:

Efficiency=(OutputPowerInputPower)×100%Efficiency = \left( \frac{Output Power}{Input Power} \right) \times 100\%

Substituting the values:

Efficiency=(18extW24extW)×100%=75%Efficiency = \left( \frac{18 ext{ W}}{24 ext{ W}} \right) \times 100\% = 75\%

Thus, the efficiency of the motor is 75%.

Step 5

Complete the following sentence by putting a cross (X) in the box next to your answer.

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Answer

B conservation of energy

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