Physics Olympiad - "Physics Cup" Problem no. 3

"Physics Cup" Problem no. 3

Determine or estimate the net heat flux density P between two parallel plates at distance L from each other, which are at temperatures T₁ and T₂, respectively. The space between the plates is filled with a monoatomic gas of molar density n and of molar mass M. You may use the following approximations:

1. The gas density is so low that the mean free path Î» >> L;

2. T₁ >> T₂.

3. When gas molecules bounce from the plates, they obtain the temperature of the respective plates (for instance, this will happen if they are absorbed/bound for a short time by the molecules of the plate, and then released back into the space between the plates).

4. You may neglect the black body radiation.

5. "Estimate" means that the numeric prefactor of your expression does not need to be accurate.

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Vivek @ Born this Way ·2011-12-14 04:01:24

Whether we could solve or not, that's not a matter but atleast we should make something out of it.

What I could make out of the following problem is :

Given that the mean free path of gas molecules is greater than the distance between the plates. It means that effectively, the path of the gas molecules is not obstructed by collision with the other gas molecules before they collide with the wall of the plates.

Now, as given, these gas molecules take the temperature of the surface they hit, so we can assume that at a certain instant of time, equal no. of gas molecules are hitting the both plates.

At the left plate, the gas molecules collect heat and at the right plate give up the heat. But the both are not equal and that is what the heat flux.

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Basic Integral Calculus Operators Symbols Matrix Cases

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° ∂ ∞ α β γ δ θ λ μ ν ξ π ρ σ φ ω ε ƒ κ τ υ Γ Δ Λ Σ Π Ω

"Physics Cup" Problem no. 3

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