Question

The first operation involved in Carnot cycle is:
A. Isothermal Expansion
B. Adiabatic Expansion
C. Isothermal Compression
D. Adiabatic Compression

Answer 1

Hint: Carnot cycle is basically an ideal reversible closed thermodynamic cycle in which the substance will undergo four successive operations. We will study about the very first operation of the Carnot cycle in which the substance interacts with the system and does some amount of work.

Complete answer:
When a system undergoes through different states successively and then finally returns to its original state is known as thermodynamic cycle. The Carnot cycle is also one such cycle which is ideal and reversible. Carnot cycle comprises of four successive operations which are listed below serially:
-Isothermal Expansion
-Adiabatic Compression
-Isothermal Compression
-Adiabatic Expansion

These operation can be shown as:

Thus the very first operation of the Carnot cycle is Isothermal Expansion where the heat is transferred reversibly from a high temperature source (reservoir) at constant temperature. During the first operation of the Carnot cycle the given gas is allowed to expand thus it does some work on the surroundings. But we can see that pressure drops from points $$1$$ to point $$2$$ but the temperature of the gas remains constant, therefore we call it isothermal expansion of gas and the process is known as isothermal expansion. Similarly other operations take place in successive order as mentioned.

Therefore the correct option is A.

Note: Carnot cycle is an example of an ideal heat engine whose efficiency is almost $$100\mathrm{\%}$$ which is practically not possible. This engine is only limited to the theoretical part. The word isothermal means at constant temperature means while during isothermal process the temperature of the system does not change, it remains constant. The above graph of Carnot engine is made between the pressure and volume variables.