Question

In a Carnot cycle, which process occurs between the two isothermal processes?

• A. Isobaric processes
• B. Isochoric processes
• C. Adiabatic processes
• D. Isenthalpic processes

Hint:

Remember the sequence of the Carnot cycle on a $T-S$ (Temperature-Entropy) diagram.
It forms a perfect rectangle with horizontal lines representing the isothermal processes and vertical lines representing the reversible adiabatic (isentropic) processes.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
This question asks about the sequence of processes that make up a Carnot thermodynamic cycle.
Specifically, we need to identify which type of process connects the two isothermal heat transfer processes.

Step 2: Key Formula or Approach:
The Carnot cycle is a highly idealized thermodynamic cycle consisting of four reversible processes:
1. Reversible isothermal expansion (heat addition at $T_{\text{high}}$)
2. Reversible adiabatic expansion (work output with temperature drop to $T_{\text{low}}$)
3. Reversible isothermal compression (heat rejection at $T_{\text{low}}$)
4. Reversible adiabatic compression (work input with temperature rise to $T_{\text{high}}$)

Step 3: Detailed Explanation:

• A Carnot cycle is represented on a pressure-volume ($P-V$) diagram as a closed loop containing two isotherms and two adiabats.

• The transition between the high-temperature isothermal expansion and the low-temperature isothermal compression is achieved via isentropic (reversible adiabatic) expansion.

• Similarly, the transition from the low-temperature isothermal compression back to the high-temperature isothermal expansion is achieved via isentropic (reversible adiabatic) compression.

• Isobaric (constant pressure), isochoric (constant volume), and isenthalpic (constant enthalpy) processes are not part of the standard Carnot cycle.

Step 4: Final Answer:
The processes occurring between the two isothermal processes in a Carnot cycle are adiabatic processes.