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Thermal Physics

Blazing goIITian

Joined:	5 Jun 2007
Post:	978

11 Jan 2008 09:46:05 IST

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364

entropy in a mess

None

the following pics are taken from resnick halliday fundamentals of physics.

They clearly say that the entropy change of the system for an irreversible process between two equilibrium states i and f (say) will be same as that for a reversible process between the same two states.This is because entropy being state function depends only on the initial and final states...and for convenience we write it as equal to that for the reversible process..as

dS_system = _{[i ]}

^{[f ]} (dQ_r/ T)........where dQ_r is the heat taken by the system in the reversible process.

Now they again say that total entropy change of system and surrounding for a reversible process will be zero and that for an irreversible process will be greater than zero.

The first part is clear...

if in a reversible process system absorbs heat dQ_r,then surrounding also loses the same heat .

So dS_surroundingfor reversible process = - _{[i ]}^{[f ]} (dQ_r/ T)

So dS_universe(reversible process)

= dS_system+ dS_surrounding=_{[i ]}^{[f ]} (dQ_r/ T) - _{[i ]}^{[f ]} (dQ_r/ T) = 0

Now how should i define dS_surrounding(for irreversible process) such that

dS_universe(irreversible process) = dS_system+ dS_surrounding> 0

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It is to be noted that dS_system = _{[i ]}^{[f ]} (dQ_r/ T) for both reversible and irreversible

process as entropy of the system is a state function and does not depend on

the path followed (read the passages)

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Comments (4)

NITESH BASKARAN

Blazing goIITian

Joined: 29 Sep 2007

Posts: 487

11 Jan 2008 18:04:40 IST

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entropy is not there in IIT portions.

biki ....

Blazing goIITian

Joined: 5 Jun 2007

Posts: 978

11 Jan 2008 23:19:03 IST

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when u open goiit...
at the top of your internet explorer remains written ----

IIT JEE , AIEEE ...... blah blah ..

So i thought of asking ...

biki ....

Blazing goIITian

Joined: 5 Jun 2007

Posts: 978

13 Jan 2008 12:38:37 IST

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ALL ARE SURE THAT THEY ARE GOING TO CRACK IIT-JEE !!!!

no aieee candidates here?????

IF YES THEN ANSWER PLEASE

biki ....

Blazing goIITian

Joined: 5 Jun 2007

Posts: 978

17 Jan 2008 23:23:00 IST

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plz answer someone .... its been ovr a week or 2 without any fruitful answer

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