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A train is powered by a diesel engine - Edexcel - GCSE Physics - Question 2 - 2013 - Paper 1

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A train is powered by a diesel engine. The diesel engine is used to turn a generator. The generator provides electricity for electric motors which drive the wheels. ... show full transcript

Worked Solution & Example Answer:A train is powered by a diesel engine - Edexcel - GCSE Physics - Question 2 - 2013 - Paper 1

Step 1

Draw one straight line from each train part to its useful energy transfer.

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Answer

For the diesel engine, the useful energy transfer is chemical to electrical. For the generator, it is electrical to kinetic. For the motor, it is kinetic to electrical.

Step 2

Calculate the amount of energy wasted in one second in the generator.

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Answer

To calculate the wasted energy, subtract the useful energy from the energy supplied:

extEnergywasted=1400extkJ−1300extkJ=100extkJ ext{Energy wasted} = 1400 ext{ kJ} - 1300 ext{ kJ} = 100 ext{ kJ}

Step 3

Calculate the efficiency of the generator.

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Answer

Efficiency is calculated using the formula:

ext{Efficiency} = rac{ ext{Useful energy}}{ ext{Energy supplied}} imes 100

Substituting the values:

ext{Efficiency} = rac{1300}{1400} imes 100 = 92.86 ext{%}

This rounds to approximately 93%.

Step 4

Suggest why the motors are painted black.

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Answer

The motors are painted black because black is a good thermal radiator, which helps to remove waste heat and prevents the motors from overheating.

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