Resistivity is a property of a material, measured in Ωm, defined as the product of the resistance of a component made of the material and its cross sectional area divided by its length at a given temperature. 


  1. Good conductors have a very low resistivity (in the order of 10-8 Ωm), insulators have a value in the order of 1016 Ωm, and semiconductors have values between these extremes.  
  2. Resistivity in metals and semiconductors generally increases with temperature.

The negative temperature coefficient (NTC) thermistor is an electrical component made from a semiconductor whose resistance falls with temperature (because the number density of charge carriers increases).