A refrigerator is a device used for cooling things. Working substance would absorb a certain quantity of heat `Q_(2)` from the sink at lower temperature `T_(2)` and reject a larger amount of heat `Q_(1)` to the source (surrounding air) at higher temperature `T_(1)` (= room temperature) with the help of an external agency supplying energy `W` to the system.
Clearly, `w=Q_(1)-Q_(2)`
Cofficient of performance of refrigerator, `beta(T_(2))/(T_(1)-T_(2)) = (1-eta)/(eta)`
Read the above passage and answer the following questions:
(i) What is the cofficient of performance of a refrigerator working between `-10^(@)C` and `25^(@)C`?
(ii) 'Refrigerator is an efficient room heater'. Do you agree with the statement? Justify.

Explanation

(i) Here, `T_(2)= -10^(@)C = (-10+273)K= 263K`
`T_(1)= 25^(@)C= (25+273)K= 298K`
`C.O.P= beta= (T_(2))/(T_(1)-T_(2))= (263)/(298-263)= (263)/(35)= 7.5`
(ii) Yes, the statement is true. This is because by consuming `W` units of energy, it delivers `Q_(1)` units of heat to the room from the condenser coils at the back of the refrigeraotr. And `Q_(1)=Q_(2)+W`, i.e., `Q_(1)gtW`. Thus, we pay for `W` units of energy and get `Q_(1)` unit of heat energy in the room, which is greater than `W`.