Differences between Ohmic conductors and non-ohmic conductors with respect to Ohm’s law, V-I graph, resistance constancy or not – are listed in this post.
difference between Ohmic & Non-Ohmic conductor
Ohmic conductors are conductors that obey Ohm’s Law. The V-I curves of these conductors are linear. Resistance is independent of Voltage and Current for these Ohmic conductors. Examples: Metals.
For vacuum tubes, p-n junction diode, thermistor, and transistors Ohm’s law doesn’t hold good even for small currents. These are called Non-Ohmic conductors. For these cases, the V/I ratio or Resistance R is not constant. Here R is dependent on the applied potential difference (V).