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Refrigerator is an example of heat pomp . All types of heat engines are capable of extracting heat from an object continuously with the help of an input energy . In a refrigerator, input energy is provided by electrical energy being used by it .

Its efficiency is measured in terms of coefficient of performance which is as follows.

COP = Heat extracted from object / Energy used by machine

Total energy given out by heat pump to surrounding is total of heat extracted and energy input.

That 600 J is total heat drained out in one cycle, and heat given as input to the pump is $W=200J$, we can find the energy taken out from the cold reservoir.

$$\begin{gathered} Q_c=Q_h−W \\ =600−200 \\ =\underset{\_}{400\mathrm{J}} \end{gathered}$$

Considering this, the refrigerator's performance coefficient will be

$$\begin{gathered} K=\frac{Q_c}{W} \\ =\frac{400}{200} \\ =2 \end{gathered}$$

$$\begin{gathered} K=\frac{Q_c}{W} \\ =\frac{400}{200} \\ =2 \end{gathered}$$