Thermodynamics and engines (A-level only)

Which is a correct statement about an ideal heat pump?

A. The coefficient of performance ( $COPhp\text{COP}_{\text{hp}}$ ) is increased when the absolute temperature of the cold reservoir is decreased while the temperature of the hot reservoir is held constant.
B. The coefficient of performance ( $COPhp\text{COP}_{\text{hp}}$ ) is always less than the coefficient of performance ( $COPref\text{COP}_{\text{ref}}$ ) of an ideal refrigerator operating between the same two reservoirs.
C. The coefficient of performance ( $COPhp\text{COP}_{\text{hp}}$ ) is 5.0 when the absolute temperature of the hot reservoir is 1.25 times the absolute temperature of the cold reservoir.

[2]

An ideal refrigerator operates with a coefficient of performance $COPref=3.0\text{COP}_{\text{ref}} = 3.0$ .

Determine the efficiency $\eta\,$ of an ideal heat engine operating between the same two thermal reservoirs.

[3]

Which is a correct statement about an ideal heat pump?

A. The coefficient of performance ( $COPhp\text{COP}_{\text{hp}}$ ) is increased when the absolute temperature of the cold reservoir is decreased while the temperature of the hot reservoir is held constant.
B. The coefficient of performance ( $COPhp\text{COP}_{\text{hp}}$ ) is always less than the coefficient of performance ( $COPref\text{COP}_{\text{ref}}$ ) of an ideal refrigerator operating between the same two reservoirs.
C. The coefficient of performance ( $COPhp\text{COP}_{\text{hp}}$ ) is 5.0 when the absolute temperature of the hot reservoir is 1.25 times the absolute temperature of the cold reservoir.

An ideal refrigerator operates with a coefficient of performance $COPref=3.0\text{COP}_{\text{ref}} = 3.0$ .

Determine the efficiency $\eta\,$ of an ideal heat engine operating between the same two thermal reservoirs.

[3]

Thermodynamics and engines (A-level only) Questions