JEE Main & Advanced Chemistry Thermodynamics / रासायनिक उष्मागतिकी The Carnot Cycle

Carnot, a French engineer, in 1824 employed merely theoretical and an imaginary reversible cycle known as carnot cycle to demonstrate the maximum convertibility of heat into work.

The system consists of one mole of an ideal gas enclosed in a cylinder fitted with a piston, which is subjected to a series of four successive operations.

For cyclic process, the essential condition is that net work done is equal to heat absorbed. This condition is satisfied in a carnot  cycle.

\[\frac{w}{{{q}_{2}}}=\frac{{{T}_{2}}-{{T}_{1}}}{{{T}_{2}}}=\]Thermodynamic efficiency

Thus, the larger the temperature difference between high and low temperature reservoirs, the more the heat converted into work by the heat engine. 

Since \[\frac{{{T}_{2}}-{{T}_{1}}}{{{T}_{2}}}<1\], it follows that \[w<{{q}_{2}}\]. This means that only a part of heat absorbed by the system at the higher temperature is transformed into work. The rest of the heat is given out to surroundings. The efficiency of the heat engine is always less then 1. This has  led to the following enunciation of the second law of thermodynamics.

It is impossible to convert heat into work without compensation.