Heat Engines, Heat Pumps and Refrigerators

The main purpose of any heat engine is ........................................... . 

• To convert heat energy into movement, W.

• To convert heat energy into internal energy, W.

• To convert heat energy into work, W.

No engine can transfer all the input heat energy into useful work. Some energy is transferred to the surroundings. Which thermodynamic law is this?

• 1st Law

• 2nd Law

Which of the following is not a perfect condition for achieving the maximum theoretical coefficient of performance?

• Energy is not needed to move internal components of the engine.

• All input heat energy is transferred into useful work

• The fuel is completely used.

• No frictional forces inside the engine

What happens in an isothermal process?

• Heat transfer at constant temperature

• All heat is transferred

• No heat is transferred at all.

• Heat is transferred at a constantly changing temperature.

What happens in an adiabatic process?

• Heat transfer at constant temperature

• All heat is transferred

• No heat is transferred at all.

• Heat is transferred at a constantly changing temperature.

In which type of expansion or compression is an adiabatic process?

• Fast expansion or compression

• Slow expansion or compression

How must heat be transferred in order for it to be an isothermal process?

• Slowly

• Rapidly

Which one of the following is the function of the expansion valve in a refrigerator?

• It compresses the vapour/gas. Some vapour is turned into a liquid.

• It causes the liquid to expanded adiabatically, Some liquid is turned into a vapour.

• It take heat energy taken from the inside of the fridge and uses it to change the liquid into vapour.

• It changes the remaining vapour into a liquid.

Which one of the following is the function of the evaporator coils in a refrigerator?

• It compresses the vapour/gas. Some vapour is turned into a liquid.

• It causes the liquid to expanded adiabatically, Some liquid is turned into a vapour.

• It take heat energy taken from the inside of the fridge and uses it to change the liquid into vapour.

• It changes the remaining vapour into a liquid.

Which one of the following is the function of the compressor in a refrigerator?

• It compresses the vapour/gas. Some vapour is turned into a liquid.

• It causes the liquid to expanded adiabatically, Some liquid is turned into a vapour.

• It take heat energy taken from the inside of the fridge and uses it to change the liquid into vapour.

• It changes the remaining vapour into a liquid.