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Thermodynamics (Physics) · Question 27

JEE Main 2025 (Online) 3rd April Evening ShiftMCQMedium📈 Topic in 13% papers+4−1
1

An ideal gas exists in a state with pressure P0, volume V0. It is isothermally expanded to 4 times of its initial volume (V0), then isobarically compressed to its original volume. Finally the system is heated isochorically to bring it to its initial state. The amount of heat exchanged in this process is

  1. P0V0( 2 - 0.75)
  2. P0V0(2 2 - 0.75)
  3. P0V0(2 2 - 0.25)
  4. P0V0( 2 - 0.25)

Answer

(2) P0V0(2 2 - 0.75)

Solution

The gas returns to its initial state (cyclic process) ⇒ U = 0, so Qnet = Wnet.

Isothermal expansion V0 4V0:

W1 = P0V0 4 = 2P0V0 2

Pressure after it: P = P0V04V0 = P04

Isobaric compression 4V0 V0:

W2 = P04(V0 - 4V0) = -0.75P0V0

Isochoric heating: W3 = 0

∴ Qnet = W1 + W2 + W3 = P0V0(2 2 - 0.75)

Answer: (2)

JEE Main 2025 (Online) 3rd April Evening Shift

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2

In an adiabatic process, which of the following statements is true?

  1. The internal energy of the gas decreases as the temperature increases
  2. The molar heat capacity is zero
  3. Work done by the gas equals the increase in internal energy
  4. The molar heat capacity is infinite
JEE Main 2025 (Online) 2nd April Morning Shift
3

Identify the characteristics of an adiabatic process in a monoatomic gas. Choose the correct answer from the options given below :

  1. (B), (D) only
  2. (B), (E) only
  3. (A), (C), (E) only
  4. (A), (C), (D) only
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4

The work done in an adiabatic change in an ideal gas depends upon only :

  1. change in its pressure
  2. change in its temperature
  3. change in its specific heat
  4. change in its volume
JEE Main 2025 (Online) 29th January Morning Shift
5

A Carnot engine (E) is working between two temperatures 473 K and 273 K. In a new system two engines - engine E1 works between 473 K to 373 K and engine E2 works between 373 K to 273 K. If 12, 1 and 2 are the efficiencies of the engines E, E1 and E2, respectively, then

  1. 12 = 1 2
  2. 12 = 1 + 2
  3. 12 1 + 2
  4. 12 < 1 + 2
JEE Main 2025 (Online) 28th January Morning Shift

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