Thermodynamics and engines (A-level only)

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 $COPref\text{COP}_{\text{ref}}$ of the refrigerator.

[4]

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 $COPref\text{COP}_{\text{ref}}$ of the refrigerator.

[4]

Thermodynamics and engines (A-level only) Questions