Skip to main content

WHAT IS THE SECOND LAW OF THERMODYNAMICS ?




First law of thermodynamics only taught us about the temporal nature of world by which we can only transfer energy or thermodynamic coordinates in each other at the rate of mechanical equivalent of heat also known as joule's equivalent which is defined as -

" we have to do 4.18 J of work to produce 1 calorie of heat "

But second law of thermodynamics give us proper understanding at which term and condition are employed by nature for transformation of thermodynamic coordinate's into primary interest for understanding of how transformation will occur between heat and work .

i want to emphasize one more point about this law, isn't a absolute law about which we will discuss in microscopic level of second law .

considerably there are four scientist's worked on second law , Rudolf Clausius , lord kelvin, max Planck & Ludwig Boltzmann , first three of them worked on classical thermodynamics also known as macro static level thermodynamic & last one worked on microscopic level of thermodynamic where actual meaning of second law lies .

Second law's foundation led by Carnot Principle which states that -

" Efficiency of heat engine depends on the two temperature between which heat engine is working and it's independent of working substance . "

second law could be expressed in many ways but dominated statement's are given by Rudolf Clausius and Lord kelvin & Max Planck .

Rudolf Clausius statement - it is impossible to construct a device which , operating in a cycle , will produce no effect other than the transfer of heat from a cooler body to hotter body

kelvin-planck statement - it is impossible for a heat engine to produce net work while working in a cycle by exchanging heat from only one thermal reservoir

One more argument is very famous about this two statement which is equivalence between them hence when we try to violate one statement other one violates simultaneously than we came on abstract both of them are logically equal statement lets see how we reached on this conclusion

First we will violate Clausius statement -

make a device which takes heat in from lower temperature reservoir and throw out it to higher thermal reservoir without expense of any external work

make a heat engine cycle according to kelvin-planck's statement connected through same reservoir

now here clearly we can see "R" is taking heat "Q" from low temperature thermal reservoir and ejecting same amount of heat to higher temperature

thermal reservoir without expense of any external work ,

and a normal Heat Engine taking heat "Q" from higher temperature thermal reservoir and producing "W" amount of work by ejecting "W-Q" amount of heat to lower temperature thermal reservoir while working in cycle .

here we encounter a fact our Refrigerator is ejecting Q amount of heat to the ThR and our heat engine taking "Q" amount of heat from ThR so, instead of interchanging heat from ThR we can join HE to each other than our system's arrangement will look something like

So this is clear that this device is working in cycle by interchanging heat through only one thermal reservoir which is violation of kelvin-planck's statement .

now come on kelvin planck's statement 's violation here we use alternative approach we will violate kelvin-planck's statement and clausius's statement will violate simultaneously

make a heat engine which is working in a cycle and producing net work while interchanging heat from only one thermal reservoir .

now in system we will add an system according to clausius statement

now care fully observe the diagram , HE is producing work by inter changing heat Q from high thermal reservoir while working in cycle and system "R" is taking heat from TLR and ejecting it to the ThR by consuming some amount of work so ,

here we will join HE output W to input of "R"

Now we can consider "R" & HE as a single device , here "R" is taking W amount of work from HE and Q' amount of heat from TLR and ejecting W+Q' to the sink ;but we know W=Q so total ejection by "R" will be Q+Q' .

But Q is the same amount of heat "R" is taking from THR so instead of interchanging it by reservoir we can give Q amount of heat directly from the HE considering it as a part of individual system

Clearly system is not consuming any work to transfer heat from low thermal reservoir to high thermal reservoir as a refrigerator .

rotation of W=Q is just happening within the system  "R"is not consuming it .

Logic behind both of these statement are energy can not be used 100% in cyclic processes

TH R = Higher temperature thermal reservoir ;

TLR = Lower temperature thermal reservoir ;

"R" = Refrigerator

HE = Heat Engine

Comments

Post a Comment

Popular posts from this blog

SUM OF INFINITE SERIES BY RAMANUJAN

I n this blog i am going to discuss about something very strange important but strange a master piece from a Indian mathematician Srinivasa Ramanujan , who who discovered something mind blowing .   So if i ask you what is the sum of all natural number more likely you will answer  "infinity" and like always genius personalities has something different opinion just like srinivasa Ramanujan . Lets see how                    1+2+3+4+5+6+7+8+9 . . . . . . Became  -1/12 Let's take a infinite series S1 -                     S 1 = 1-1+1-1+1-1+1-1+1-1+1 . . . . . . lets do little maneuver with it like we always do in mathematics -  S1 = (1-1)+(1-1)+(1-1)+(1-1)+(1-1)+(1-1). . . . . .  we are just taking brackets at first on "plus one" and than closing it after...
Post a Comment
Read more

DIFFRENCE BETWEEN HEAT AND WORK !

H EAT and WORK plays vital role in thermodynamics. Its very common misunderstanding between peoples that they are ENERGY but they are not energy they are medium by which we transfer energy   .  although they d on't seem to be identical because heat   is thermal property and work is mechanical property but they are same  , at microscopic level they both are same phenomenon .     HEAT   They are just moving of molecules , having difference is only , heat is moving of molecules disorderly in any direction OR in other words heat is microscopic collision of molecules . WORK   Work is moving of molecules  in only single direction OR in other words work is m acroscopic push and pulls ( given by product of force and displacement ) . both shares same SI unit as JOULE . We termed work as high grade energy and heat as low grade energy  Because in reversible or irreversible process we can convert work 100 % in heat ...
Post a Comment
Read more

WHAT IS NANOTECHNOLOGY ?

N anotechnology is the science of manipulation of matter according to our need at the Nanoscale of the order of 10^-2 . it have tremendous possibilities in near future because of its ability of making advance material  with unique chemical property which suits according to condition   .  This term technically first time introduced by physicist Richard Feynman in 1959 in his lecture with topic of There is plenty of room at the bottom . but at that time technology was not enough to implementation of his idea in practical application's . Primarily there is two type of approaches we use to construct anything  - I)  Top-to-bottom approach  II) Bottom-to-top approach Top-to-bottom approach :- when we cutoff resource to make our desirable shape is known as Top-to-bottom approach ; Ex- wooden chair .  Bottom-to-top approach :- when we construct structure by starting from its minute cells to approaching required shape of structure is known...
Post a Comment
Read more