JEE Main 2021 · 25 February · evening · Single correct · +4 / −1

Thermodynamic process is shown below on a P-V diagram for one mole of an ideal gas. If V₂ = 2V₁ then the ratio of temperature T₂/T₁ is :

JEE Main PYQ figure
  1. (a) √2
  2. (b) 1/√2
  3. (c) 1/2
  4. (d) 2
Answer and solution

Answer (a) √2

Solution

Physics sir · 3 steps

Swap P for nRT/V in the curve's equation and you get a direct rule linking T and V.

  1. Use the gas law. For one mole of ideal gas, P = RT/V. Put this into the process equation PV^(1/2) = constant.

    RT/V V^(1/2) = constant ⇒ T/√V = constant ⇒ T ∝ √V

  2. Put in numbers. T₂/T₁ = √(V₂/V₁) = √(2V₁/V₁) = √2.
  3. So. The temperature rises by a factor of √2, which is option (a).

The idea to keep. For any process PVⁿ = constant, substitute P = nRT/V to get TVⁿ⁻¹ = constant. Then any temperature ratio follows from the volume ratio.

Answer from the NTA final answer key. Solution by PrepWiser.

Study Thermodynamics

Asked about 150 times in JEE Main since 2020. This question is from 2021.