MCQEasyJEE 2025Isothermal & Adiabatic Processes

JEE Physics 2025 Question with Solution

Match List-I with List-II.

A matching table with List-I thermodynamic processes Isothermal, Adiabatic, Isobaric, Isochoric and List-II characteristics $$\Delta W = 0$$, $$\Delta Q = 0$$, $$\Delta U \neq 0$$, $$\Delta U = 0$$.

Choose the correct answer from the options given below :

  • A

    (A)-(III), (B)-(II), (C)-(I), (D)-(IV)

  • B

    (A)-(IV), (B)-(I), (C)-(III), (D)-(II)

  • C

    (A)-(IV), (B)-(II), (C)-(III), (D)-(I)

  • D

    (A)-(II), (B)-(IV), (C)-(I), (D)-(III)

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: List-I contains the thermodynamic processes (A) Isothermal, (B) Adiabatic, (C) Isobaric, and (D) Isochoric.

Find: The correct matching with the characteristics in List-II and hence the correct option.

From the given solution:

  • Isothermal process occurs at constant temperature, so for an ideal gas
ΔT=0ΔU=0\Delta T = 0 \Rightarrow \Delta U = 0

Hence, (A) \rightarrow (IV).

  • Adiabatic process has no heat exchange with surroundings
ΔQ=0\Delta Q = 0

Hence, (B) \rightarrow (II).

  • Isobaric process occurs at constant pressure. In general, internal energy changes, so
ΔU0\Delta U \neq 0

Hence, (C) \rightarrow (III).

  • Isochoric process occurs at constant volume, therefore work done is zero
ΔW=PΔV=0\Delta W = P\Delta V = 0

Hence, (D) \rightarrow (I).

So the complete matching is:

  • (A)-(IV)
  • (B)-(II)
  • (C)-(III)
  • (D)-(I)

This corresponds to option (3). Therefore, the correct option is C.

Process-wise Explanation

Given: A match-the-following question on basic thermodynamic processes.

Find: Which option gives the correct correspondence between each process and its defining characteristic.

Step 1: Use the defining condition of each process.

For an isothermal process, temperature remains constant:

ΔT=0\Delta T = 0

For an ideal gas, internal energy depends only on temperature. Therefore,

ΔU=0\Delta U = 0

So, (A) \rightarrow (IV).

For an adiabatic process, no heat is transferred:

ΔQ=0\Delta Q = 0

So, (B) \rightarrow (II).

For an isobaric process, pressure remains constant:

ΔP=0\Delta P = 0

In such a process, internal energy can change, so the listed characteristic is

ΔU0\Delta U \neq 0

So, (C) \rightarrow (III).

For an isochoric process, volume remains constant:

ΔV=0\Delta V = 0

Hence, work done is

ΔW=PΔV=0\Delta W = P\Delta V = 0

So, (D) \rightarrow (I).

Step 2: Compare with the options.

The matching obtained is (A)-(IV), (B)-(II), (C)-(III), (D)-(I), which is exactly option (3).

Conclusion: The correct option is C.

Common mistakes

  • Confusing isothermal with adiabatic. This is wrong because isothermal means constant temperature, whereas adiabatic means no heat exchange. Always identify the defining quantity first: isothermal gives ΔT=0\Delta T = 0 and adiabatic gives ΔQ=0\Delta Q = 0.

  • Assuming isochoric means no change in internal energy. This is wrong because constant volume only implies zero work done, not necessarily zero internal energy change. Use ΔW=PΔV\Delta W = P\Delta V, so when ΔV=0\Delta V = 0, only ΔW=0\Delta W = 0 follows.

  • Using the wrong property for an isobaric process. This is wrong because isobaric means constant pressure, not constant internal energy. In general, for an isobaric process, ΔU\Delta U can be non-zero, so match it with ΔU0\Delta U \neq 0 here.

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