Why Is Isothermal Expansion Answer D in Homework Problems?

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Homework Help Overview

The discussion revolves around a conceptual question related to isothermal expansion in thermodynamics, specifically addressing why a particular answer is deemed correct in a homework problem context.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the reasoning behind the correct answer, questioning the implications of isothermal processes on heat transfer and internal energy. There is a focus on understanding why isothermal expansion is favored over other processes, such as adiabatic processes.

Discussion Status

Some participants have provided insights into the nature of isothermal and adiabatic processes, discussing the relationship between heat transfer and entropy. There appears to be a productive exploration of different interpretations regarding the effects of these processes on the system.

Contextual Notes

Participants are navigating the nuances of thermodynamic principles, particularly the second law of thermodynamics and its implications for entropy in different processes. There is an acknowledgment of the constraints posed by the homework problem's structure and the need for clarity in reasoning.

Arun Raja
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Homework Statement


http://puu.sh/c09sc/b1d02302bd.png

Homework Equations


Conceptual question.

The Attempt at a Solution


The answer is isothermal expansion(D).
but heat does not decrease due to isothermal process and expansion leads to lesser collision of particles on walls of container.
So why D?
 
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Is not your question really, "Why not A, B, or C?

The compression processes are intuitively obvious? Adiabatic processes do not transfer heat or matter.
 
even isothermal processes occur at same temperatures. So there is no increase in internal energy which leads to increase in entropy.
 
Think of it with this equation from the 2nd law of thermodynamics:

ΔS = Q/T

For adiabatic processes, Q = 0.
For isothermal processes, entropy of the system will increase if the system is expanding because Q must be positive (heat goes into the system) for the system to remain isothermal. If the system is compressed isothermally, heat must go out of the system and entropy will decrease.
 

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