Ncert Exercises & Solutions

If the coefficient of performance of a refrigerator is 5 and it operates at room temperature (27°C), find the temperature inside the refrigerator.

Hint: The refrigerator delivers the heat to the room at a higher temperature.

Step 1: Use the formula of coefficient of performance of the refrigerator.

Given, the coefficient of performance,

(β) = 5

T_{1} = (27 + 273) K = 300 K, T_{2} = ?

Coefficient of performance,

(β)

= \frac{T_{2}}{T_{1} - T_{2}}

5 = \frac{T_{2}}{300 - T_{2}} \Rightarrow 1500 - 5 T_{2} = T_{2}

\Rightarrow 6 T_{2} = 1500 \Rightarrow T_{2} = 250 K

\Rightarrow T_{2} = (250 - 273) ° C = - 23 ° C