Question

Please note that this is per second and not per minute.
A steam engine delivers 5.4×108 J of work per minute and services 3.6 × 109 J of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per second?

Answer 1

Work done by the steam engine per minute, W= 5.4 × 108 J

Heat supplied from the boiler, H = 3.6 × 109 J

Efficiency of the engine = Output energy / Input energy

∴ η = W / H  =  5.4 × 108 / (3.6 × 109)  =  0.15

Hence, the percentage efficiency of the engine is 15 %.

Amount of heat wasted = 3.6 × 109 – 5.4 × 108

= 30.6 × 108 = 3.06 × 109 J

Therefore, the amount of heat wasted per minute is 3.06 × 109 J.