Concepts to remember on Mobility and temperature dependence of resistivity: Current and Electricity

Key Concepts

• Drift velocity: the average velocity of charge carriers in a conductor.

• Mobility: the measure of how quickly charge carriers move in response to an applied electric field.

• Resistivity: the opposition to the flow of electric current in a material.

• Temperature dependence of resistivity: the change in resistivity of a material with temperature.

Mobility and Resistivity

• Resistivity is inversely proportional to mobility. If the mobility of charge carriers increases, the resistivity decreases, and vice versa.

Temperature dependence of resistivity:

Metals:

• As temperature increases, the thermal vibrations of the metal atoms increase, which interfere with the movement of charge carriers (electrons).

• This increased interference causes the resistivity of the metal to increase with temperature.

Semiconductors:

• As temperature increases, the number of charge carriers (electrons and holes) in a semiconductor increases due to the breaking of covalent bonds.

• The increased number of charge carriers decreases the resistivity of the semiconductor.

Insulators:

• The resistivity of insulators remains relatively constant with temperature changes. They have very few free carriers, and those are bound within atoms.

• The changes in resistivity with temperature are very small and often negligible compared to metals and semiconductors.