Thermodynamic Processes — A/L Physics

How do I practise Thermodynamic Processes?

1 question with a worked solution

1. During an adiabatic expansion of an ideal gas, which equation correctly describes the relationship between the heat exchanged with the surroundings (ΔQ), change in internal energy (ΔU), and work done by the gas (ΔW)?
   1. A) ΔQ = 0 and ΔW = -ΔU (Work is done entirely at the expense of internal energy)
   2. B) ΔU = 0 and ΔQ = ΔW (Internal energy remains strictly constant)
   3. C) ΔW = 0 and ΔQ = ΔU (No mechanical work is performed)
   4. D) ΔQ = ΔU + 2ΔW
   Check my answer

   Correct answer: A) ΔQ = 0 and ΔW = -ΔU (Work is done entirely at the expense of internal energy)

   By definition of an adiabatic process, there is no heat exchange with the environment (ΔQ = 0). Applying the First Law of Thermodynamics (ΔQ = ΔU + ΔW) yields 0 = ΔU + ΔW => ΔW = -ΔU. During adiabatic expansion (ΔW > 0), the internal energy decreases (ΔU < 0), causing the gas to cool.

   Show worked solution

   Step 1: Adiabatic condition: ΔQ = 0. Step 2: First law of thermodynamics: ΔQ = ΔU + ΔW. Step 3: 0 = ΔU + ΔW => ΔW = -ΔU. Answer: ΔQ = 0 and ΔW = -ΔU (Work is done entirely at the expense of internal energy).
   Modelled on: the A/L Physics examination pattern

Get this auto-marked

Next in the syllabus

Where does Thermodynamic Processes fit in the syllabus?

Unit 4.8 · Year 1 · Term 2