Complete Question
A real (non-Carnot) heat engine, operating between heat reservoirs at temperatures of 650 K and 270 K and performs 4.3 kJ of net work and rejects 8.00 kJ of heat in a single cycle. The thermal efficiency of this heat engine is closest to A) 0.35 B) 0.31. C) 0.28. D) 0.38. E) 0.42.
Answer:
The correct option is A
Explanation:
From the question we are told that
   The first operating temperature is  [tex]T_1 = 650 \ K[/tex]
   The second operating temperature is  [tex]T_2 = 270 \ K[/tex]
   The net workdone is  [tex]W = 4.3 \ kJ = 4.3 *10^{3} \ J[/tex]( output of the engine )
   The amount of heat energy rejected is  [tex]H = 8.00 \ kJ = 8.00 *10^{3 } \ J[/tex]
Generally a heat engine convert heat from a high temperature  to mechanical energy and then reject the remaining heat so the absorbed by the engine  is Â
             [tex]W + H[/tex]
Generally the thermal  efficiency is mathematically represented as
   [tex]\eta = \frac{out}{In} * 100[/tex]
Here out is the output of the engine
and  in is the input of the engine
   [tex]\eta = \frac{W}{W + H} * 100[/tex]
=> Â [tex]\eta = \frac{4.3}{4.3 + 8} * 100[/tex]
=> Â [tex]\eta = 0.35[/tex]
