Tuesday, January 1, 2013

Non-Ohmic Devices or Limitations of Ohm's Law

Ohm’s law has been found valid over a large class of materials, there do exist materials and devices used in electric circuits where the proportionality of V and I does not hold. Such conductor are called non Ohmic conductors.  The deviations broadly are one or more of the following type  V ceases to be proportional to I

The relation between V and I depends on the sign of V. In other words, if I is the current for a certain V, then reveres the direction of V keeping its magnitude fixed, does not produce a current of the same magnitude as I in the opposite direction.

The relation between V and I is not unique, i.e., there is more than one value of V  for the same current I. A material exhibiting such behaviour is GaAs.

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