A steam engine delivers 5.4 × 10^{8} \, {J} ...

Thermodynamics

Question : 7 of 10

Marks: +1, -0

A steam engine delivers

5.4 \times 10^{8} \, \text{J}

of work per minute and services

3.6 \times 10^{9} \, \text{J}

of heat per minute from its boiler. What is the efficiency of the engine? How much heat is wasted per minute?

Solution:

Useful work done per min (output)

= 5.4 \times 10^{8} \, \text{J}

Heat absorbed per min (input)

= 3.6 \times 10^{9} \, \text{J}

Efficiency

= \frac{\text{Output}}{\text{Input}}

= \frac{5.4 \times 10^{8}}{3.6 \times 10^{9}} = 0.15

= 0.15 \times 100 \, \% = 15 \, \%

Heat energy wasted per minute = Heat energy wasted per useful work done per minute

= 3.6 \times 10^{9} - 5.4 \times 10^{8}

= 3.06 \times 10^{9} \, \text{J} \, \text{min}^{-1}

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