# Calculate these 5 temperatures along this Thermodynamic cycle

• Seeit
In summary, the conversation discusses the relationship between temperatures T1, T2, T3, and T4 in a system with ideal gas and an inverse proportionality between pressure and volume. Using this information and equations, it is possible to calculate the temperature of T2 as 2T1, but the temperatures of A and C cannot be determined without more information. It is suggested that A and C are on the same isotherm and therefore have the same temperature.
Seeit
Homework Statement
Calculate the temperatures at places 2, 4, A, B and C if you know:
It's an ideal diatomic gas
T3 = 4T1
T2 = Tb = T4
The axis connecting 1, B and 3 crosses zero.
Relevant Equations
pV = nRT
Laws of thermodynamics

I only know T3 = 4•T1
I was able to calculate the T2 = Tb = T4
I built four equations:
T2 = p2V1 / nR
T4 = p1V2 / nR
p1/T1 = p2/T2
V1/T2 = V2/4T1

I put them together and got T2 = 2T1

I can't figure out the temperatures of A and C. I tend to think Ta could equal Tc (then I would be able to calculate it), but I am not sure.

Last edited:
Helo @Seeit ,
Are you sure you have rendered the complete problem statement ? I would expect some more information, like: ideal gas, isothermal (or adiabatic), ...

I also miss an equation of state in your relevant equations (e.g. ##\ pV = NRT##).

Seeit said:
I only know ##T_3 = 4T_1##
How ? Or was that a given ? (In that case it is part of the problem statement)
Same for ##T_2 = T_b = T_4## ?

What about the scale and the axes of the diagram ?

##\ ##

Seeit and Lnewqban
Welcome, @Seeit !

As post #1 has been edited to answer @BvU questions, I suggest considering two things:

-The inverse proportionality between p and V.
-The similarity between polygons 1CBA and 1234 due to the axis connecting 1, B and 3, which makes their corresponding sides proportional.

Seeit and BvU
Lnewqban said:
Welcome, @Seeit !

As post #1 has been edited to answer @BvU questions, I suggest considering two things:

-The inverse proportionality between p and V.
-The similarity between polygons 1CBA and 1234 due to the axis connecting 1, B and 3, which makes their corresponding sides proportional.

View attachment 324057
So am I right about thinking that A and C are on the same isotherm and have therefore the same temperature?

Seeit said:
So am I right about thinking that A and C are on the same isotherm and have therefore the same temperature?
Correct!

Seeit

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