All Questions
Tagged with mean-free-path kinetic-theory
21
questions
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Mean free path equation for plasma
Does the mean free path equation
$$\lambda=\frac{1}{\sqrt{2}\pi d^2 n_v}$$
work for collisions in plasma or just for gas?
- 33
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1
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57
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How is number of collisions per unit distance related to mean free path?
Recently I have been studying Kinetic Theory Of Gases, with one of the topics as collision frequency. I know that collision frequency is inverse of relaxation time which is also the measure of number ...
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1
answer
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Mean free path of molecules
So in the book concepts in thermal physics(by Stephan and Katherine Blundell) the expression of mean scattering time is derived as shown(please refer the book for more). If we replace vdt in the ...
- 353
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Why is the sphere of influence of the molecule in mean free path a cylinder?
In my book for deriving mean free path a cylinder is taken to act as a sphere of influence of molecules with which it could bump into other molecules and its radius = diameter of the molecule we are ...
- 648
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1
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How does $\frac{\langle v\rangle}{\langle v_r\rangle}=\frac{1}{\sqrt2}$ imply the formula for the mean free path?
In this question, it was asked how the formula $$l=\frac{1}{\sqrt 2n\sigma }$$ can be rigorously derived for a Maxwell-Boltzmann gas.
Here $l$ is the mean free path length in a gas, $n$ is the gas ...
- 1,440
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Collisional cross-section from attenuation factor
I am trying to find the mean free path of silver atoms travelling through air (I am given the temperature, pressure and that they are attenuated by a factor $2.72$ in a distance of $10^{-2}$m).
I know ...
- 75
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Ratio of mean free paths between two equal volumes at different temperature, separated by a partition with pinhole
Question:
A container is divided into two equal parts I and II by a partition with a small hole of diameter $d$. The two partitions are filled with same ideal gas, but held at temperatures $T_I$= ...
- 1,022
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Which average are we taking in a rigorous calculation of the mean free path in a gas?
This is a question at one level beyond the standard introductions to kinetic theory. I want to know which average we are taking when we talk about a mean free path in a gas. I recently read
Steve T. ...
- 59.6k
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1
answer
233
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Why is mean free path independent of mass?
In this page of Hyperphysics, I am puzzled as to why there isn't any mass dependence in the expressions for mean free path.
Here are the two equations as mentioned in the website:
When only one ...
- 7,980
1
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1
answer
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How to calculate the free mean path of electrons in the gas mixture? [closed]
How to calculate the free mean path of electrons in the gas mixture? I understand (a little bit) the mean free path concept for the atomic collisions but I am not sure what to do if I am interested in ...
user148787
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1
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454
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How can mean free path affect the propagation of sound in a gas?
I was thinking, since mean free path is a measure of "how long" a particle has to travel to collide with another, that this surely must influence sound propagation somehow. I would say this ...
- 353
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vote
3
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In particle physics what is the derivation of the mean free path length: $\ell=\frac{1}{n \sigma}$?
From my lecture notes (ICL, dept. of Physics) it is written:
Consider a thin piece of material with thickness $d$ containing target particles with number density $n$, as illustrated in Figure $\bf{2....
- 2,470
1
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1
answer
369
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Why does thermal conductivity decrease from solids to gases?
I am learning in my heat transfer class that the thermal conductivity decreases from solids to liquids to gases i.e.
$$K_{solid} > K_{liquid}>K_{gas}$$
The reason cited is that (based on my ...
user238352
19
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3
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Rigorous derivation of the mean free path in a gas
Can anyone supply me with a derivation of the mean free path, of
particles in a Maxwell Boltzmann Gas?
Cited in various literature is the formula,
\begin{align}
\begin{split}
\ell&=\frac{1}{\...
- 579
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vote
2
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Most probable free path length
The distribution of scattering time is
$nv\sigma e^{-nv\sigma t}$
where $\sigma$ is the collision-cross section, $n$ is the number density of molecules and $v$ is the average relative velocity. This ...
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