Question

The coefficient of performance of a refrigerator is 5.0.

A. If the compressor uses 10 J of energy, how much heat is exhausted to the hot reservoir?
B. if the hot reservoir temperature is 27 degrees Celsius, what is the lowest possible temperature in degrees Celsius of the cold reservoir?

Answer 1

`Q_x=60\ J`

`T_L=-23\ ^(\circ)C` is the lowest possible temperature of the cold reservoir.

Step-by-step explanation:

Given:

Coefficient of performance of refrigerator,
`COP=5`

A)

We know that for a refrigerator:

`\rm COP=( desired\ effect )/(\: energy\ supplied )`

Given that 10 J of energy is consumed by the compressor:

`5=(desired\ effect)/(10)`

`\rm Desired\ effect=50\ J`

Now the by the conservation of energy the heat exhausted :

`Q_x=50+10`

`Q_x=60\ J`

B)

Also

`COP=(T_L)/(T_H-T_L)`

where:

`T_H\ \&\ T_L` are the absolute temperatures of high and low temperature reservoirs respectively.

`5=(T_L)/((273+27)-T_L)`

`1500-5* T_L=T_L`

`T_L=250\ K`

`T_L=-23\ ^(\circ)C` is the lowest possible temperature of the cold reservoir.