A sample of an ideal gas may: expand adiabatically or expand isothermally. The net flow of heat into the gas from the exterior is:
Correct answer: D. Zero in I and positive for II
- A. Positive in each case
- B. Negative for I and positive for II
- C. Positive for I and negative for II
- D. Zero in I and positive for II
Explanation
An adiabatic process, has no heat transfer (Q=0). For an isothermal expansion, the internal energy does not change (ΔU=0), but the gas does work (W>0). According to the first law (ΔU = Q - W), Q must be positive to equal the work done.
Last updated
About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
Practise Thermodynamics
714 free Thermodynamics MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Physics questions like this
Physics is on 13 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
Related questions
110 J of heat is added to a gaseous system, whose internal energy change is 40 J, then the amount of external work done is
1st law of thermodynamics is consequence of conservation of
A Carnot engine operates between reservoirs at 600 K and 300 K. Its maximum possible efficiency is
A carnot engine working between 200k and 400k has a work output of 600 J per cycle. How much heat energy is supplied to the engine from the source of each cycle.
A chemical system is sealed in a strong rigid container at room temp and then heated vigorously change in work done during the process is: