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.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
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.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Physics questions like this
Physics is on 16 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More First Law of Thermodynamics questions
The internal energy of a system during an isothermal process:
In which process the entire heat supplied to the gas is converted to the internal energy of the gas?
All the heat supplied to a system is converted into work in the process.
The heat rejected by a Carnot engine operating between 600 K and 300 K with 2000 J of heat input is:
The energy input to an engine is four times greater than the work it performs. What is its thermal efficiency?
The efficiency of a heat engine in terms of the temperature of the reservoir and sink is defined as: