# Pressure temp relationaship

My lecturer writes the following in his lecture notes:

" P $$\propto$$ t for a fixed volume of gas,
P = P0(1+$$\alpha$$t)

Using the Celcius scale of temperature, we find $$\alpha \cong$$ 1/273."

Is P really proportional to t?

How do we find $$\alpha \cong$$ 1/273 using the Celcius temp scale?

## Answers and Replies

mgb_phys
Homework Helper
My lecturer writes the following in his lecture notes:
" P $$\propto$$ t for a fixed volume of gas,
Correct

P = P0(1+$$\alpha$$t)
Just another way of writing the above,

Is P really proportional to t?
Yes - for an ideal gas or at low pressure and reasonable temperatures.

How do we find $$\alpha \cong$$ 1/273 using the Celcius temp scale?
Experimentally - it's the definition of absolute zero

If P $$\alpha$$ t for a fixed volume of gas, then should P not equal $$\alpha$$ t, instead of being equal to a constant P-nought times the sum of 1 and $$\alpha$$ t?

Experimentally - it's the definition of absolute zero

How can it be the definition of absolute zero?