# + instead of - for Maxwell Relation?

• pivoxa15
In summary, the conversation is discussing a possible error on the last page of lecture notes regarding the second realization relation. It is suggested that the link be fixed and the individual has realized they used the wrong dQ and should have used dQ=dU-dW instead of dQ=dU+dW. There is also a mention of potential inconsistencies in defining dQ and dW.
pivoxa15
In the lecture notes

http://webraft.its.unimelb.edu.au/64...n/lecture3.pdf

on the very last page, should the second realisation relation have -(dU/dp) instead of the + (dU/dp)?

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You need to fix the link. I get a 404 error.

Here is the site. Click on lecture 3 go to teh last page

http://webraft.its.unimelb.edu.au/640322/pub/notes/common.html

I fixed up the error I think it is on this page and have edited my OP accordingly.

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I have derived it again and realized that I used the wrong dQ. It should have been dQ=dU-dW whereas I used dQ=dU+dW.

First Law applications can be an enormous pain in the ass - some people sometimes define dQ and dW as either done ON the system or done BY the system quite arbitrarily - which of course changes their sign.

## 1. What is the purpose of using + instead of - in the Maxwell Relations?

The use of + instead of - in the Maxwell Relations is to indicate the direction of the change in variables when calculating thermodynamic quantities. It represents an increase in one variable while the other variable remains constant.

## 2. How do the Maxwell Relations differ from other thermodynamic equations?

The Maxwell Relations are a set of equations that relate the partial derivatives of thermodynamic variables to each other, while other thermodynamic equations such as the first and second laws of thermodynamics relate the change in thermodynamic variables to energy and work.

## 3. Can the Maxwell Relations be derived from other thermodynamic equations?

Yes, the Maxwell Relations can be derived from other thermodynamic equations such as the first and second laws of thermodynamics and the fundamental thermodynamic relation.

## 4. Why are the Maxwell Relations important in thermodynamics?

The Maxwell Relations are important in thermodynamics because they provide a way to calculate thermodynamic quantities without directly measuring them. They also help to simplify complex thermodynamic systems by relating various thermodynamic variables to each other.

## 5. Are the Maxwell Relations valid for all thermodynamic systems?

Yes, the Maxwell Relations are valid for all thermodynamic systems, regardless of their complexity. They are fundamental equations in thermodynamics and can be applied to all types of thermodynamic processes.

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