Conservation and dissipation of energy
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An electric winch is labelled with its power input.

a.

What does power input mean?

Select one option:

  • The electrical charge transferred each second through the winch motor.
  • The electrical energy transferred each second to the winch motor.
  • The average potential difference across the winch motor.
  • The electrical current flowing through the winch motor.
[1]
b.

Write down the equation which links current, potential difference and power.

[1]
c.

An electric winch motor has a power input of 1850 W1850 \text{ W}1850 W. The mains potential difference is 240 V240 \text{ V}240 V.

Calculate the current in the winch motor. Round your answer to 2 significant figures.

[3]
d.

Table 1 shows information about three different electric winches.

Electric winchTotal power input in wattsUseful power output in wattsEfficiency
P3002400.80
Q12009000.75
R800kkk0.72

Write down the equation which links efficiency, total power input and useful power output.

[1]
e.

Calculate the value of kkk in Table 1.

[2]
f.

In addition to power input, electric winches should also be labelled with their useful mechanical power output. Suggest why this is important for a consumer.

[2]

Conservation and dissipation of energy Questions

Practise AQA GCSE Physics Conservation and dissipation of energy with exam-style questions for Foundation and Higher tier. 29 questions covering Energy transfers in a system and Efficiency, matched to the AQA GCSE Physics (8463) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.

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Conservation and dissipation of energy Questions

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