Question

An inventor tries to sell you his new heat engine that takes in 40 J of heat at 87°C on each cycle, expels 30 J at 27°C, and does 10 J of work. Would it be wise to invest in this engine?

Answer 1

Answer:

NOT WISE

Explanation:

given,

T₁ = 87⁰C  =  273 + 87 = 360 K

T₂ = 27⁰C  =  273 + 27 = 300 K

work output given = 10 J

efficiency will be equal to :

   $\eta = 1 - \dfrac{T_2}{T_1}\\\eta = 1 - \dfrac{300}{360}\\\eta = 0.166$

output delivery =  η ₓ input

                          =  0.166 ₓ 40  

                          = 6.66 J

hence, the output of new engine  is less than the old one so, investing in new engine will not be feasible.