# Absolute Zero on celsius scale

• arya_jsr

#### arya_jsr

Hi ,

If 20 KJ are added to a carnot cycle at a temperature 100 degree Celsius and 14.6 KJ are rejected at 0 degree Celsius,determine the location of absolute zero on celsius scale?

Ans -270.16 C

Please tell me how to solve it

Regards
Arya

Hi Arya, welcome to PF. What do you know about the Carnot cycle relationships between extracted work, rejected heat, and the temperatures of the hot and cold reservoirs?

Hi Arya, welcome to PF. What do you know about the Carnot cycle relationships between extracted work, rejected heat, and the temperatures of the hot and cold reservoirs?

Hi Mapes,
In carnot cycle suppose Q1 is given as heat input and T1 is temperature of source,and
Q2 is rejected heat at temperature T2(Temperature of sink),then (Q1/T1)=(Q2/T2) and if W is the work done by reversible cyclic heat engine then Q1=Q2+W.
Now please tell me how to solve this problem
regards
Arya

The Efficiency is defined as:

$$E=\frac{Q_h-Q_c}{Q_h}$$

Qh is the heat extracted and Qc is the head expelled.

Then, we can derive using basic thermodynamic laws that the efficiency of the Carnot Cycle is given by:

$$E=1-\frac{T_c}{T_h}$$

Where Th is the temperature of the hot reservoir and Tc is the temperature of the cold reservoir. Can you figure it out from here?

Hi Mapes,
In carnot cycle suppose Q1 is given as heat input and T1 is temperature of source,and
Q2 is rejected heat at temperature T2(Temperature of sink),then (Q1/T1)=(Q2/T2) and if W is the work done by reversible cyclic heat engine then Q1=Q2+W.

Looks good. Now $T_1$ and $T_2$ are measured from the absolute zero of the system, which is a variable for this problem. So you can't just use 100°C and 0°C; rather, you need to reference these to the absolute zero variable. Then solve the equation for this variable.

Thanks My Friend Mapes,
I got it ,it solved my problem.Actually i was not taking absolute zero as a variable .Now i have solved it.Thanks
regards
Arya