Saturday, July 20, 2013

Electronics - Fluid Analogy Resistance

A good way to visualize electricity is to relate it to the movement of fluids. They have a lot of similarities as we will discuss below.


ΔV = -IR

This is simply stating that the change in voltage is the current multiplied by the resistance. The way we can think about this is that the voltage loss is due to the current passing through a volume more difficulty, otherwise known as resistance. We can show the resistance with the equation


Where rho is the resistivity due to impediments in the material, multiplied against the length, divided by the area.



This is the change in pressure due to an increase in resistance. We can visualize this increase in pressure by thinking about water flow through a pipe. Let us think about a large pipe transitioning to a smaller one. The change in pressure from the area before the small pipe to after the small pipe can be approximated by thinking about the smaller pipe as a resistive element, similar to resistance in a current. However instead of impediments as a function of the material, it is just the smaller size of the pipe. Therefore the resistance in this case would be proportional to (1/A) where A is the area of the smaller pipe.

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