How does the relationship between I and U change when the material of the conductor changes? (Ohm’s Law)

Answer

Dear Julia,

A material has electrical properties that determine its conductivity. For a conductor we call this the conductivity (symbol sigma). If the material changes, the conductivity will also change. For a metal the conductivity is very high (about a million) for an insulator it can be very small.

Ohm’s law applies to a complete conductor. The resistance R herein is determined by the conductivity. For a homogeneous wire, we can determine the resistance using Pouillet’s law (a homogeneous wire is a wire that has the same conductivity everywhere).

R = (1/sigma) * (length in meters) / (cross-section of the conductor in m^2)

This way you can determine the resistance of each conductor. This is also possible for non-homogeneous conductors, but it is somewhat more difficult.

I hope this answers your question,

Yves