PhysicsJEE Main 8 Apr 2026, Shift 2·Q10·MCQ·Moderate

Thermodynamics · Laws of thermodynamics

One mole of diatomic gas having rotational modes only is kept is a cylinder with a piston system. The cross-section area of the cylinder is

4\ \mathrm{cm^2}

. The gas is heated slowly to raise the temperature by

1.2\ ^\circ

C during which the piston moves by 25 mm. The amount of heat supplied to the gas is J. (Atmospheric pressure

= 100

kPa,

R = 8.3

J/mol.K) (Neglect mass of the piston)

(1)24.8
(2)25
(3)15.04
(4)29.98

Flawed question. The data are inconsistent: with a free piston at 100 kPa, $P\Delta V$ must equal $nR\Delta T = 9.96$ J, but a 25 mm travel gives 1.0 J; no option equals the consistent $Q = 34.9$ J, and the key 25 is only the option nearest to $24.9 + 1.0 = 25.9$ J. It is shown for completeness and is left out of practice tests.

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Thermodynamics · Laws of thermodynamics

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