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Thermodynamics and engines (A-level only)

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Question 7
a.

Which is a correct statement about an ideal heat engine?

  • A. The efficiency is increased when the kelvin temperatures of both the hot source and the cold sink are increased by equal amounts.
  • B. The maximum efficiency depends on the working substance used in the engine.
  • C. The efficiency is 75% when the kelvin temperature of the hot source is four times the kelvin temperature of the cold sink.
[2]
b.

An ideal heat engine has an efficiency of 0.20. The same engine works in reverse as an ideal refrigerator between the same hot and cold spaces.

Determine the coefficient of performance COPref\text{COP}_{\text{ref}}COPref​ of the refrigerator.

[4]
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Thermodynamics and engines (A-level only) Questions

  1. A Level
  2. /Physics
  3. /Thermodynamics and engines (A-level only)

29 exam-style questions on AQA A Level Physics Thermodynamics and engines (A-level only), covering First law of thermodynamics (A-level only), Non-flow processes (A-level only), The $p$ - $V$ diagram (A-level only), Engine cycles (A-level only), Second Law and engines (A-level only), and Reversed heat engines (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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