Resistance and Resistivity

What is resistance measured in

Ohms

What is Ohms law

V = IR

How does changing the length of a wire change its resistance

The longer the wire the more difficult for current to flow through so the resistance increases

How does changing the area of a wire change its resistance

The thicker the wire the easier for electrons to pass through therefore lowering the resistance

What is resistivity

A property of the material which measures how much it resists current flow

What is resistivity measured in

Ohm meters

What factors effect resistivity

Structure of the material

Temperature

Light intensity

How does increasing the temperature increase the resistivity in metals

Heating the metal causes the ions to vibrate more which makes the free electrons collide more.

How does increasing the temperature effects the resistivity in metals

Increases the resistivity

How does increasing the temperature effects the resistivity in semi-conductors

Decreases the resistivity

How does increasing the temperature decrease the resistivity in metals

Causes more charge carriers to be released

How do you calculate resistivity in the practical

Measure the current and potential difference at different lengths and plot resistance against length. Calculate the area and multiply by the area.