# What is the Difference Between an Ohmic and Non-Ohmic Conductor?

Ohmic conductors are characterized by the fact that the set voltage $$U$$ on the ohmic conductor is proportional to the electric current $$I$$, where the proportionality constant is the electric resistance $$R$$:
If the voltage $$U$$ is doubled, then the current $$I$$ through the conductor is also doubled.
Non-Ohmic conductors, on the other hand, are all conductors that do not satisfy Ohm's law 1. This means that the doubling of the voltage $$U$$ does not have to result in the doubling of the current $$I$$. In illustration 2, the U-I graphs of non-ohmic conductors are sketched as examples: Transistor graph (1), gas discharge graph (2) and diode graph (3).