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Thermodynamics (Physics)

JEE Main 2025 (Online) 28th January Morning ShiftMCQMedium📈 Topic in 3% papers+4−1
Ques. 1JEE Main 2025, 28 January (Morning Shift)

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

Answer

(4) 12 < 1 + 2

Solution

Carnot efficiency: = 1 - T2T1

12 = 1 - 273473 = 200473 0.423

1 = 1 - 373473 = 100473 0.211

2 = 1 - 273373 = 100373 0.268

1 + 2 0.479 > 12

(In general 1 - 12 = (1 - 1)(1 - 2) 12 = 1 + 2 - 1 2)

12 < 1 + 2

Answer: (4)

Keep practising — Thermodynamics (Physics)

Ques. 2JEE Main 2025, 24 January (Morning Shift)

An ideal gas goes from an initial state to final state. During the process, the pressure of gas increases linearly with temperature. Choose the correct answer from the options given below:

  1. A, C Only
  2. A, D, E Only
  3. E Only
  4. A, B, C, D Only
Ques. 3JEE Main 2025, 24 January (Morning Shift)

The temperature of 1 mole of an ideal monoatomic gas is increased by 50 at constant pressure. The total heat added and change in internal energy are E1 and E2, respectively. If E1E2= x9 then the value of x is .

Ques. 4JEE Main 2025, 24 January (Evening Shift)

The magnitude of heat exchanged by a system for the given cyclic process ABCA (as shown in figure) is (in SI unit) : [figure]

  1. zero
  2. 40
  3. 5
  4. 10
Ques. 5JEE Main 2025, 24 January (Evening Shift)

Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the correct answer from the options given below :

  1. Both (A) and (R) are true and (R) is the correct explanation of (A)
  2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
  3. (A) is false but (R) is true
  4. (A) is true but (R) is false
Ques. 6JEE Main 2025, 23 January (Morning Shift)

Match List - I with List - II Choose the correct answer from the options given below:

  1. A-I, B-III, C-II, D-IV
  2. A-I, B-IV, C-II, D-III
  3. A-III, B-I, C-IV, D-II
  4. A-III, B-IV, C-I, D-II
Ques. 7JEE Main 2025, 23 January (Morning Shift)

An ideal gas initially at 0 temperature, is compressed suddenly to one fourth of its volume. If the ratio of specific heat at constant pressure to that at constant volume is 3/2, the change in temperature due to the thermodynamic process is K.

Ques. 8JEE Main 2025, 23 January (Evening Shift)

Water of mass m gram is slowly heated to increase the temperature from T1 to T2. The change in entropy of the water, given specific heat of water is 1 J kg-1 K-1, is :

  1. m(T2-T1)
  2. zero
  3. m ( T1T2 )
  4. m ( T2T1 )
Ques. 9JEE Main 2025, 23 January (Evening Shift)

[figure] Using the given P-V diagram, the work done by an ideal gas along the path ABCD is :

  1. 3P0 V0
  2. -3P0 V0
  3. -4P0 V0
  4. 4P0 V0
Ques. 10JEE Main 2025, 22 January (Evening Shift)

Given are statements for certain thermodynamic variables, Choose the correct answer from the options given below :

  1. C and D Only
  2. A and B Only
  3. D and A Only
  4. B and C Only

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