Question

A Carnot engine absorbs 1000 J of heat from the reservoir at 127° C and rejects 600 J of heat during each cycle. Calculate the efficiency of the engine.
1. 40%
2. 20%
3. 10%
4. 25%

Answer 1

Correct Answer - Option 1 : 40%

CONCEPT:

• The efficiency of a heat engine is defined as the ratio of the net work done by the engine in one cycle to the amount of heat absorbed by the working substance from the source.

The efficiency of a heat engine is given by:
\(η = 1- \frac{Q_2}{Q_1}\) (where Q₂ is heat reject and Q₁ is the heat absorbed )

CALCULATION:

Given Q1= 1000 J,Q₂ = 600 J  

We know the efficiency of a heat engine is:

\(η = 1- \frac{Q_2}{Q_1}\)=\(1- \frac{600}{1000}\)= 0.4 = 40% (on putting the value we get )

Hence the efficiency of a heat engine is given by  40%