Must see in cyclic process(Its not 22.22%)

Plot a curve b/w P vs V
plot:

A(V0,P0)
B(V0,3P0)
C(3V0,P0)

join A, B, C with straight lines
Find Efficiency

46 Answers

3
iitimcomin ·

GUD QUESTION I THINK IT WILL BE CLEAR FOR EVERYONE BY DRAWING DA ISOTHERM!!!!!!!!!!!!!!!!WHICH IS Y D IS REQ..........CHECK DA PIC

33
Abhishek Priyam ·

A->B->C

1
dimensions (dimentime) ·

why r u saying ans is not 22.22%

i am getting ξ=22.22% ..............

33
Abhishek Priyam ·

Oh i got the first one who gave the answer which i wanted...

Its not 22.22%

Gave the table above

33
Abhishek Priyam ·

Think more about process B->C..

A question on same concept was asked in recent AITS...
They saw this question :P

1
dimensions (dimentime) ·

see in process B->C temp at B & C will be equal,
so ΔU = 0,
work done in BC = heat given =4P0V0

what is wrong in this ???????????/

33
Abhishek Priyam ·

No in BC heat is +ve frm B->D and -ve from D->C

So work done u should have got is 2P0V0

and +ve heat is for A->B B->D

Find D first...

1
dimensions (dimentime) ·

well yes u r right,

i missed that one ..............

1
skygirl ·

yes right priyam...
they saw this question :P :)

nothing is wrong ... but we are bothered with the positive heat gained in the process B->C ...

wat do u think abt that ? .. the heat supplied n the heat extracted in BC ??

i firstly took it zero.. which is obviously wrong...

did you find the +ve heat in BC? if yes, then plz tell how..

33
Abhishek Priyam ·

Well i am posting T V graph it might help

33
Abhishek Priyam ·

9
Celestine preetham ·

sorry priyam i was rong u are right

1
dimensions (dimentime) ·

& what is the direction of process

i.e is it from A->B->C , or C->B->A

specify them also..........

3
iitimcomin ·

A QUITE FAMOUS QUESTION IS TO FIND DA MAX. TEMPERATURE IN SUCH A PROCESS ITS ACTUALLY IN DA CENTER OF bc MANY CONFUCE IT TO BE IN B,C!!!!!!!!!!!!!!!!!!

3
iitimcomin ·

JUST ANOTHER NICE XAMPLE TO DEPICT THIS ......... IF U LUK AT DA PROCESS CHOWN IN MAH DIAGRAM ULL SEE DA EFFICIENCY IS 100% .....(IF CB WERE TO BE ADIABATIC).....
HEHE IF THIS WERE POSSIBLE THERE WOUDNT BE AN ENERGY CRISIS TODAY LOL!!!!!

62
Lokesh Verma ·

This is one of the best physics discussions on this forum.!

(I dont know what has been happening in "Colors" :P

3
iitimcomin ·

thanx for the pinks sir!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

62
Lokesh Verma ·

I have a doubt. I have seen this thread for long...

What is the reason why D will be the point uptil which there will be heat supplied..

That is the point where the temperature starts to decrease

What about P work?

Dont we have to find the point after which the Net HEAT Supplied becomes -ve??? (I mean elementray net heat supplied!)

I think D is some other point?

What do you say?

33
Abhishek Priyam ·

us samay bhi bole the.. phir hum kuch kiye the... par point nahi nikla tha.. :(

phir physics ke naam par... bich wala point......

62
Lokesh Verma ·

I think

we want the point where dQ becomes zero

so nCdT+Pdv = 0

so we want nC+PdV/dT = 0

we know V in terms of T ...

Now can this be solved?

33
Abhishek Priyam ·

hmm. haan kar ke dekhte hainnn

33
Abhishek Priyam ·

:O

bahut ganda aane laga... :(

solve karne ka man nahi kaar raha ...
phir se himmat karnege...

3
iitimcomin ·

sir ...I HAVE THE FOLLOWING PROOF

Tmax is at MIDPOINT OF BC..........................

P-3P0/V-V0 = 3P0- P0/V0-3V0 .................

P-3P0 = -(V-V0) P0/V0 P = P0 + 3P0 - P0V/V0 ...

P = 4P0 - P0/V0 *V ...............

PV = RT .....

4P0V - P0/V0V2 = RT ........

DIFFERENTIATE WRT T ...............

4P0dV/dT - P0/V0(2V) dV/dT = R .............

for maxima dT/dV = 0.............

4P0 - P0/V0(2V) = 0 V = V0/2 !!!!!!!!!!!

SO AT V = V0/2 WE HAVE T = Tmax ................

also at T=Tmax dU=0 as theres no difference in heat !!!!!!!!

and at that point work done is 0

we have Q = 0!!!!!!!!!!!!!!!! [1]

9
Celestine preetham ·

ln3 / 5 + ln3 * 100 ≈ 18%

1
Kumar Saurabh ·

2/3 that is

1
Kumar Saurabh ·

no no my mistake..

2PV/4PV = 50%

I do 2PV/3PV

33
Abhishek Priyam ·

ξ=W/(Heat absorbed) in bw answer is wrong and ha sorry gas is diatomic

1
Kumar Saurabh ·

i am still thinking i am correct.

i will give picture why

Here efficiency will be equals 2PV/ (2PV+2PV) = 1/2 = 50%

33
Abhishek Priyam ·

33
Abhishek Priyam ·

Any one try this.........

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