Asked in PMC Practice Test 14 (2021) 2021Moderate

A refrigerator operates for a certain time, and the work done by the electrical energy during this time is W = 1000 J. What can be said about the heat delivered to the room containing the refrigerator?

Correct answer: C. The heat delivered to the room is greater than 1000 J

  • A. The heat delivered to the room is less than 1000 J
  • B. The heat delivered to the room is equal to 1000 J
  • C. The heat delivered to the room is greater than 1000 J
  • D. No heat is delivered to the room

Explanation

The refrigerator uses electrical energy for cooling, however, since it is not ideal, efficiency will not be 100% and will create waste energy in the form of heat sound etc, therefore, "heat delivered to the room will be greater than 1000 J".

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About First Law of Thermodynamics

The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.

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