Resistivity and mobility

Resistivity and Resistance 

Resistivity and mean free path 

Thermal and drift velocity 

Mobility and mean free path 

Electron transport quantities in metal 

How good is the Drude model 

Evolution of the models that describe resistivity 

Resistivity before Drude model  

What Ohm actually discover  

More about Ohm's law discovery 

What Kirchhoff and Maxwell discovered 

Band theory and beyond 

 Resistivity is property of the material not the geometry

I-V curves for battery,  filament bulb, resistor, diode, thermistor      Definition of resistance        

Resistivity of a material can depend on temperature or light:

Thermistor has negative temperature coefficient (NTC ): when temperature increases then resistivity decreases

Incandescent bulb or metals have  positive ( PTC ):  when temperature increases then resistivity increases  

Light dependent resistor (LDR): When light  intensity increases then resistivity decreases