Wed May 09, 2012 By:

which conductors do not obey the ohm's law?

Expert Reply
Wed May 09, 2012
Tungsten is an example of a conductor that does not obey Ohm's Law. If you were to plot a graph of current against voltage, over a range of voltages, you will find that the result is a curve - showing that current is not directly proportional to voltage, which is the requirement for Ohm's Law. 

While the ratio of voltage to current will indicate what the resistance happens to be for that particular ratio, you will find that, for tungsten, that ratio continually changes as you increase voltage - proving that tungsten does not obey Ohm's Law. The general rule is that if there is no straight-line relationship between voltage and current, then Ohm's Law doesn't apply. 

Semiconductors have very low resistance values when passing current in the forward direction, and very high resistance when not passing current in the backward direction, but, at any given value of current and voltage, they still abide by the fundamental laws of nature, including Ohm's Law. 

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