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NDA 2026
Exam
NDA
Year
2026
Subject
General Ability
Chapter
General Science

NDA 2026 · General Ability · General Science

For an ideal gas, a process is described by P = kT , where k is a...

For an ideal gas, a process is described by P=kTP = kT, where kk is a constant. If the molar heat capacity for this process is CC, then which one of the following is correct (where the symbols have their usual meanings)?

Options

  1. AC=CPC = C_P
  2. BC=CVC = C_V
  3. CC=(CP+CV)/2C = (C_P + C_V)/2
  4. DCC is never constant

Correct answer

B. C=CVC = C_V

Step-by-step solution

The ideal gas equation for nn moles is PV=nRTPV = nRT.

Given the process equation P=kTP = kT, where kk is a constant.

Substituting PP into the ideal gas equation, we get:

(kT)V=nRT(kT)V = nRT

V=nRkV = \dfrac{nR}{k}

Since nn, RR, and kk are constants, the volume VV is constant. Thus, the process is isochoric.

For an isochoric process, the work done dW=PdV=0dW = P dV = 0.

From the first law of thermodynamics, dQ=dU+dW=dUdQ = dU + dW = dU.

Since dU=nCVdTdU = nC_V dT and dQ=nCdTdQ = nC dT, we have:

nCdT=nCVdTnC dT = nC_V dT

C=CVC = C_V

Answer: C=CVC = C_V
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