# Absolute Zero on celsius scale

1. Apr 15, 2009

### 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

2. Apr 15, 2009

### Mapes

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?

3. Apr 16, 2009

### arya_jsr

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

4. Apr 16, 2009

### Matterwave

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?

5. Apr 16, 2009

### Mapes

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.

6. Apr 16, 2009

### arya_jsr

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