Question

A Steam engine delivers 5.4 x 10⁸ J of work per minute and services 3.6 x 10⁹ J of heat per minute from its boiler. what is the efficiency of the engine ? How much heat is wasted per minute?

Answer 1

Output, i.e., useful work done per minute = 5.4 x 10⁸ J

Input i.e., heat absorbed per minute = 3.6 x 10⁹ J

Efficiency = Output/Input = 5.4 x 10⁸/3.6 x 10⁹ = 0.15 = 0.15 x 100% = 15%

Heat energy wasted/minute

= Heat absorbed/minute - Useful work done /min.

= 3.6 x 10⁹ - 5.4 x 10⁸ = 10⁹ (3.6 x 0.54 ) = 3.06 x 10^-9 J.