Question

In thermodynamics, for an isochoric process, which one of the following statement is INCORRECT?

• A. Energy exchanged is used to do work and also to change internal energy.
• B. It is a constant volume process.
• C. No work is done in the process.
• D. Temperature of the system changes during the process.

Hint:

Always read the question stem carefully for words like INCORRECT or NOT. It's easy to look at option (B) or (C), recognize them as true facts about an isochoric process, and select them mistakenly without reading the entire question!
center Isochoric $\implies \Delta V = 0 \implies W = 0 \implies Q = \Delta U$ center

Answer 1

The Correct Option is A

Step 1: Understand the question.
We must pick the INCORRECT statement about an isochoric process. Isochoric means the volume stays constant.
Step 2: Recall the meaning of isochoric.
Iso means same and choric refers to volume, so an isochoric process is a constant volume process. This makes the option calling it a constant volume process correct.
Step 3: Find the work done.
Work done by a gas is $W = P\,\Delta V$. Since the volume does not change, $\Delta V = 0$, so $W = 0$. The statement that no work is done is correct.
Step 4: Apply the first law of thermodynamics.
The first law says $Q = \Delta U + W$. With $W = 0$, this becomes $Q = \Delta U$. So all heat exchanged goes only into changing the internal energy.
Step 5: Spot the wrong claim.
One option says the energy is used both to do work and to change internal energy. But we just showed no work is done, so this statement is wrong.
Step 6: State the answer.
The incorrect statement is that the energy is used to do work and also to change internal energy. \[ \boxed{\text{Energy used to do work and change internal energy (incorrect)}} \]