Teaching Physics with the Physics Suite

Edward F. Redish

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Transports of delight

In this semester we have considered two "transport equations" -- equations that describe something moving across space as a result of differences in the value of some variable:

(a) In both of these cases, the resistance depends on the shape of the material, but they depend on it in different ways. For each case describe how the resistance depends on the shape of the object doing the resisting (length along the flow, L, and area perpendicular to the flow, A) and explain the mechanism of why each behaves the way it does.

(b) Fourier's law is often written as ΔT =  where φ = Φ/A. If we do this, how does R depend on L and A? Considering situations where we want to manage heat flow, discuss why this form of the equation might be more convenient that the one quoted above.

Page last modified December 13, 2008: M24