0
$\begingroup$

In kinetic theory, the thermal conductivity of a gas is $$K = \frac{1}{3} C vl.$$ In deriving this formula, why is the following equation valid?

"Now $ \Delta T$ between the ends of a free path of the particle is given by $$ \Delta T = \frac{dT}{dx}l_x $$ where $\tau$ is the average time between collisions."

This is found in Kittel, chapter 5. Thank you!

$\endgroup$
1
$\begingroup$

If you assume that there is a uniform temperature gradient $\text{d}T/\text{d}x$ along some path of length $l_x$ then the temperature difference between the two ends of the path is $\text{d}T/\text{d}x \cdot l_x$.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.