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Electrical resistance 
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#1
Apr2109, 11:10 AM

P: 26

lets say i have a block of material, measures a,b,c (length width height) and two wires running in from the top, both with circular cross section, radius r, distance d from the edges
Or, lets create a more general problem: lets say i have a space filled with material, measurements infinite (fills up all the space), specific resistance known, and two wires (isolated from the material) (sames as before, circular cross section and radius r) running in from infinity with end points at distance L.
what i'm actually trying to understand is how electric current moves in human body if i would place electrodes on the skin and apply some voltage, but the geometry of this is nontrivial, which i have not seen before while solvin 'find the resistance of blah blah blah' kind of problems thanks for any hints 


#2
Apr2109, 11:56 AM

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P: 8,954

Resistance = rho * L / A
rho is the resistivty of the material L is the distance between the points A is the cross section area 


#3
Apr2109, 11:19 PM

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PF Gold
P: 1,767

Is it AC or DC current? Do the wires run through the whole bulk of the material or are they just probes on the surface?
If they are just probes, then I think you could probably estimate them as cylinders or points of potential and solve something like a Poisson's equation to find the voltage field. If you it is an AC current with wires that penetrate through then it could be easily estimated by solving for the fields of a simple twisted pair transmission line in a lossy medium (provided you estimate the bulk to be infinite). I think it all depends on how you want to model this. 


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