Consider the following processes: I. Energy flows as heat....

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Homework Help Overview

The problem involves analyzing three processes related to energy transfer and work in thermodynamic systems. Participants are tasked with identifying which of these processes are never found to occur, with multiple-choice answers provided.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants question the correctness of the original answer choice, with some expressing confusion about why it is deemed incorrect. Others suggest that the terminology used in the question may lead to misunderstandings regarding the nature of the system described.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the question and the implications of the processes described. Some have suggested that the question may be misleading due to its phrasing, prompting further examination of the underlying concepts.

Contextual Notes

There is a suggestion that the question may be conflating the terms "system" and "heat engine," which could affect the understanding of the processes involved. Additionally, references to the second law of thermodynamics are made, indicating that certain assumptions about reservoirs and efficiency are under consideration.

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Homework Statement



Consider the following processes: I. Energy flows as heat from a hot object to a colder object II. Work is done on a system and an equivalent amount of energy is rejected as heat by the system III. Energy is absorbed as heat by a system and an equivalent amount of work is done by the system .Which are never found to occur?
A. Only I
B. Only II
C. Only III
D. Only II and III
E. I, II, and III
ans: C

Homework Equations

The Attempt at a Solution


Why its C??
 
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Any Help said:

Homework Statement



Consider the following processes: I. Energy flows as heat from a hot object to a colder object II. Work is done on a system and an equivalent amount of energy is rejected as heat by the system III. Energy is absorbed as heat by a system and an equivalent amount of work is done by the system .Which are never found to occur?
A. Only I
B. Only II
C. Only III
D. Only II and III
E. I, II, and III
ans: C

Homework Equations

The Attempt at a Solution


Why its C??
It is wrong. That's why.
 
Chestermiller said:
It is wrong. That's why.
I mean why it is wrong?
 
Any Help said:
I mean why it is wrong?
This is the same thing as an isothermal expansion, which you can always do. What they erroneously neglected to consider is this can never be done for a system operating in a cycle using a single (isothermal) reservoir.
 
Any Help said:
I mean why it is wrong?
It looks like whoever wrote the question is using the word system to mean heat engine. Try calculating the efficiency of the described engine.
 
vela said:
It looks like whoever wrote the question is using the word system to mean heat engine. Try calculating the efficiency of the described engine.
Another requirement is that there be only one reservoir to supply heat (and no reservoir to remove heat). This is basically the Kelvin statement of the 2nd law.
 

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