An inventor claims to have invented a heat engine that operates between the temperatures of 627°c and 27°c with a thermal efficiency of 70%. comment on the validity of this claim.

Answer Explanation:

the efficiency of the the engine is given by=1-

where T₂= lower temperature

           T₁= Higher temperature

we have given efficiency =70%

lower temperature T₂=27°C=273+27=300K

higher temperature T₁=627°C=273+627=900K

efficiency=1-

                =1-

                 =1-0.3333

                 =0.6666

                 =66%

66% is less than 70% so so inventor claim is wrong

answer:

(b)

explanation: