Refrigeration Cycle Steps

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Questions and Answers

Where is heat rejected by the refrigerant in a refrigeration cycle?

  • Cold chamber
  • Condenser (correct)
  • Hot chamber
  • Evaporator

What happens to the refrigerant as it passes through the nozzle in a refrigeration cycle?

  • It remains a liquid state but at a lower pressure.
  • It remains as a liquid but with an increased pressure.
  • It solidifies due to the decrease in temperature.
  • It expands into a low-pressure area, reducing in pressure and temperature, turning into a gas. (correct)

What does the second law of thermodynamics deal with?

  • Heat (correct)
  • Momentum
  • Energy
  • Work done

What percentage of the energy is extracted from the cold reservoir if the coefficient of performance (COP) of a refrigerator is 5?

<p>25% (C)</p> Signup and view all the answers

If a working substance in a heat engine absorbs 3000 J from the hot reservoir and 2250 J are wasted per cycle, what is the efficiency of the engine?

<p>75% (B)</p> Signup and view all the answers

Where does the refrigerant absorb heat at constant pressure in a refrigerator cycle?

<p>Inner compartment of the fridge (D)</p> Signup and view all the answers

What happens to a diamagnetic material when placed in a uniform magnetic field?

<p>It acquires a net induced magnetic moment opposite to the field (D)</p> Signup and view all the answers

Which property is conserved according to the first law of thermodynamics?

<p>Energy (C)</p> Signup and view all the answers

What type of material is diamagnetic?

<p>Weakly repelled by magnets (B)</p> Signup and view all the answers

How does a refrigerator release heat to the air outside in a refrigeration cycle?

<p>Through an isobaric compression process (D)</p> Signup and view all the answers

In a given thermodynamic process on an ideal gas where dW  0 and dQ  0, what happens?

<p>The pressure remains constant (D)</p> Signup and view all the answers

What does the coefficient of performance of a refrigerator measure?

<p>Efficiency in cooling (A)</p> Signup and view all the answers

What is the purpose of a compressor in a refrigeration cycle?

<p>To raise temperature through adiabatic compression (A)</p> Signup and view all the answers

What is the external work done on the working substance in a refrigerator cycle if 20% of the energy is extracted from the cold reservoir?

<p>10% (B)</p> Signup and view all the answers

Which law of thermodynamics relates to the extraction of energy from the cold reservoir in a refrigerator?

<p>Second law (D)</p> Signup and view all the answers

What is the coefficient of performance (COP) of a refrigerator when 20% of the energy extracted from the cold reservoir is used as external work?

<p>5 (A)</p> Signup and view all the answers

In a refrigeration cycle, what type of process occurs when the condenser temperature decreases?

<p>Isentropic (C)</p> Signup and view all the answers

How does the efficiency of a heat engine relate to the coefficient of performance (COP) of a refrigerator?

<p>They are inversely proportional (D)</p> Signup and view all the answers

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Study Notes

Refrigeration Cycle

  • Heat is rejected by the refrigerant in the condenser.
  • The refrigerant expands and its pressure and temperature decrease as it passes through the nozzle.

Thermodynamics

  • The second law of thermodynamics deals with the direction of spontaneous processes.
  • The coefficient of performance (COP) of a refrigerator measures its efficiency in transferring heat from the cold reservoir to the hot reservoir.

Energy Efficiency

  • If the COP of a refrigerator is 5, 20% of the energy is extracted from the cold reservoir, and 80% is used as external work.
  • The efficiency of a heat engine is 25% if it absorbs 3000 J from the hot reservoir and 2250 J are wasted per cycle.

Refrigeration Process

  • The refrigerant absorbs heat at constant pressure in the evaporator.
  • A refrigerator releases heat to the air outside through the condenser.

Magnetic Materials

  • Diamagnetic materials are repelled by a uniform magnetic field.

Laws of Thermodynamics

  • The first law of thermodynamics states that energy is conserved.
  • The second law of thermodynamics relates to the extraction of energy from the cold reservoir in a refrigerator.

Thermodynamic Processes

  • If dW = 0 and dQ = 0, the process is an isometric and adiabatic process.
  • The COP of a refrigerator measures the ratio of heat transferred from the cold reservoir to the work input.

Compressor Function

  • The purpose of a compressor in a refrigeration cycle is to increase the pressure and temperature of the refrigerant.

Work and Energy

  • If 20% of the energy is extracted from the cold reservoir, 80% is used as external work.

Refrigerator Performance

  • If the condenser temperature decreases, the refrigeration process becomes more efficient.
  • The efficiency of a heat engine is inversely proportional to the COP of a refrigerator.

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