ECAT Physics — Heat and Thermodynamics
Heat and Thermodynamics is part of the Physics section of the UET ECAT (30 of the 100 MCQs). It breaks into 3 subtopics, and we hold 33 ECAT-pattern practice MCQs on it, each with a written explanation. Tap a subtopic below to practise just that.
Subtopics (3)
How Heat and Thermodynamics is tested
Across the 7 ECAT past papers on ParhaiKrlo, Heat and Thermodynamics accounts for 10 questions. It appears in 5 of them, about 2 questions a paper. The heaviest was ECAT Past Paper 05, with 3 questions, and the most recent is ECAT Past Paper 07, with 1.
| Paper | Questions |
|---|---|
| ECAT Past Paper 07 | 1 |
| ECAT Past Paper 06 | 1 |
| ECAT Past Paper 05 | 3 |
| ECAT Past Paper 03 | 2 |
| ECAT Past Paper 02 | 3 |
Heat and Thermodynamics MCQs from the ECAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · ECAT Past Paper 07 · Heat and Thermodynamics
A mixture of two gases at constant temperature contains molecules of mass m₁ (rms speed c₁) and mass m₂ (rms speed c₂). The ratio c₁/c₂ is:
- A.m₁/m₂
- B.m₂/m₁
- C.(m₁/m₂)^(1/2)
- D.(m₂/m₁)^(1/2)
Show answer
Answer: D. (m₂/m₁)^(1/2) — Same T → same average KE: ½m₁c₁² = ½m₂c₂², so c₁/c₂ = √(m₂/m₁).
- Q2 · ECAT Past Paper 06 · Heat and Thermodynamics
On a hot summer day, the temperature in a big hall is measured a few minutes after the air conditioners are switched on. If the temperature near the floor is T₁ and near the ceiling is T₂, which statement is true?
- A.T₁ < T₂ because of Boyle's law
- B.T₁ < T₂ because of Charles's law
- C.T₁ > T₂ because of Boyle's law
- D.T₁ > T₂ because of Charles's law
Show answer
Answer: B. T₁ < T₂ because of Charles's law — Warmer air expands (Charles's law), becomes less dense and rises; cool air sinks to the floor.
- Q3 · ECAT Past Paper 05 · Heat and Thermodynamics
A mixture of two gases at constant temperature contains molecules of two kinds: the first of mass m₁ and rms speed c₁, the second of mass m₂ and rms speed c₂. The ratio c₁/c₂ is:
- A.m₁/m₂
- B.m₂/m₁
- C.(m₁/m₂)^(1/2)
- D.None of these
Show answer
Answer: D. None of these — Same temperature means equal average KE: ½m₁c₁² = ½m₂c₂², so c₁/c₂ = √(m₂/m₁), which is not listed.