A Carnot heat engine has an efficiency of `10%`. If the same engine is worked backward to obtain a refrigerator, then find its coefficient of performance.

Options

A. `8`
B. `9`
C. `6`
D. `5`

Answer

B

Explanation

`eta = 1-(T_2)/(T_1),(T_1)/(T_2) = 1/(1-eta)`
`omega = (T_2)/(T_1-T_2) = (1)/((T_(1)//T_(2))-1)`
`=(1)/([1//(1-eta)]-1) = (1-eta)/(eta)`
as `eta = 10% = 0.1, omega = (1-0.1)/(0.1) = 9` .