A. Ohmic Conductor

Example of an ohmic conductor would be a metal conductor.

B. Filament Lamp

A filament bulb’s resistance increases as it gets hotter.

C. Thermistor

The resistance of this thermistor decreases as it gets hotter. It is called a negative temperature coefficient (NTC) thermistor. It is the most common type of thermistor.

 

D. Diode

 

So filament lamps, thermistors and diodes do not have fixed resistances. The resistance varies with different p.d.s applied across them.

The resistance of the component at any p.d. can be found from these graphs at any particular point by finding the ratio V/I.

Note that this is NOT the same as finding the gradient of the line.

D.C. Circuits