Non-ohmic devices

Or limitations of ohm’s law

 

 

1) some devices and materials which are used in circuits do not obey the ohm’s law are called non-ohmic materials.


2) Some such non-ohmic devices are semiconductors, light emitting diode (LED), electrolytic solutions, transistors etc.


3) We know ohm’s law tells that

V = IR

 





But this ratio is not constant for some devices.

4)



 

The dotted line represents the ideal ohm’s law. The solid line is an identity of good conductor of electricity

 

  

5)

 



In some cases, when there is a current I for a potential difference V. if same potential V is applied in opposite direction, then the current value I is not the same as previous in forward direction. 

 


Junction diode is a well known example of this class of non-ohmic device.

  

 

 

6)



In some cases, there is more than one values of potential V for the same amount of current I.



An example of this class of non-ohmic device is  GaAs   LED.