- #1

etotheipi

2019 Award

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## Main Question or Discussion Point

Earlier I was trying to explain to one of my siblings why current is constant in a series connection (invoking that if it weren't we would have an accumulation of charge, etc.), however to give a more intuitive picture I tried to describe the hydraulic model of electric circuits, representing a resistor as a constriction in a pipe. The analogues of potential and current were fluid pressure and flow rate respectively.

However, on the spot I couldn't come up with a satisfactory explanation for the pressure (i.e. voltage) drop. If it is to behave like it's electrical analogue, we would expect a permanent drop in fluid pressure between both ends of the constriction. Yet as far as I am aware, if the cross-sectional areas of the pipe are equal before and after the constriction (and if we ignore changes in height), by Bernoulli's principle the pressures before and after the constriction should also be equal!

I reasoned that "turbulence effects" would result in the pressure drop, however this on its own doesn't lend itself particularly nicely to a neat calculation of the size of the pressure drop. I was wondering if I am on the right track here?

Thanks for your help!

However, on the spot I couldn't come up with a satisfactory explanation for the pressure (i.e. voltage) drop. If it is to behave like it's electrical analogue, we would expect a permanent drop in fluid pressure between both ends of the constriction. Yet as far as I am aware, if the cross-sectional areas of the pipe are equal before and after the constriction (and if we ignore changes in height), by Bernoulli's principle the pressures before and after the constriction should also be equal!

I reasoned that "turbulence effects" would result in the pressure drop, however this on its own doesn't lend itself particularly nicely to a neat calculation of the size of the pressure drop. I was wondering if I am on the right track here?

Thanks for your help!