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R = rho L / A

by oneplusone
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Mar12-14, 07:35 PM
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When can you use this formula?
On page 13 it uses it here:

however my instructor said that you can only use it when you are using a wire and the current is flowing parallel to the axis.
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Simon Bridge
Mar12-14, 09:45 PM
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That sounds right - it only works for a nice geometry.

consider a rectangular plate LxWxT dimensions (length x width x thickness)
the resistance between opposite corners won't be ##\rho L/WT##

Even if I attach the wires to the center of areas WxT, imagine W=T=1000m ... how does the current travel through the resistor then?

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