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In terms of superconductivities and diodes (I do not know anything else except these), Ohm's law deviate from a linear relation. I search many titles or tags for this but I did not understand properly how it becomes. I wonder somethings related with this.

  • What is the basic of this deviation?

  • How it is deviate?

  • Why there is linear relation for metal conductors, if is it true?

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    $\begingroup$ Many physics things are linear under certain approximations and limits. Some things aren't. Explaining why semiconductors may (or may not) obey Ohm's "Law" takes a good intro to semiconductor physics. Note that capacitors and inductors don't obey Ohm's law either, and they aren't even weird materials. $\endgroup$
    – Jon Custer
    Apr 5 '16 at 14:11
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Ohm's law is a misnomer. It is not actually a true law, in the sense of Coulomb's of Ampère's; rather it is a 'rule of thumb' that applies pretty well in most circumstances. You will certainly not get a nobel price for finding an exception! A more general form of Ohm's law is $$\mathbf{J} = \sigma \mathbf{E},$$where $\mathbf{J}$ is the current density, $\sigma$ the conductivity and $\mathbf{E}$ the electric field. Now in this form, you can easily find a classical derivation, due to Drude, (which is totally inaccurate but does make some good qualitative predictions

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Ohms law states that the voltage and current will maintain a linear relationship under the pretenses that the material is kept at the same physical condition. This often falters at higher voltages/current because of the material increases in temperature resulting in micro changes to the way electrons move.

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  • $\begingroup$ This does not answer the question, which focuses on the reason why ohm's law isn't universally linear. You only mention that it is, without any detailed justification. Can you elaborate on the last phrase (" micro changes to the way electrons move")? $\endgroup$
    – user191954
    Jun 2 '18 at 5:16

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