Heat flows from a reservoir at `373 K` to a reservoir at `273 K` through a copper rod as shown in the figure. The heat then leaves the `273 K` reservoir and enters a Carnot engine, which uses part of this heat to do work and rejects the remainder to a third reservoir at `173 K`. What fraction of the heat leaving the `373 K` reservoir is rendered unavilable for doing work, as compared to the situation where a Carnot engine is connected directly between the `373 K` and `173 K` reservoirs ? ltbr.

Options

A. `3%`
B. `10%`
C. `17%`
D. `35%`

Answer

C

Explanation

With reservatiors at `273 K, 173 K`:
`(W)/(Q) = (273 - 173)/(273) = 0.37`
With reservoirs at `373 K, 173 K`:
`(W)/(Q) = (373 - 173)/(373) = 0.54`
1W' - W = (0.54 - 0.37)Q = 0.17 Q`