A level revision

Conductivity and resistivity

Resistivity and conductivity are a measure of how well a material resists or conducts an electric current respectively. It is important to note that the difference between resistivity and conductivity and resistance and conductance. Measurements of a materials resistivity and conductivity apply to all samples of that material anywhere whereas measurements of resistance and conductance only apply to the sample or object which is being measured.

Resitivity

As mentioned resisitivity is a measurement of how much a material resists an electric current. It is calculated using the formula:

Where is the resistivity, R is the resistance, A is the cross sectional area and L is the length of the material. The units of resistivity are Ohm metres ([/expr]m)

Conductivity

Just as conductance is the reciprocal of resistance, conductivity is the reciprocal of resistivity, therefore the formula for conductivity is:

Where is the conductivity, G is the conductance, A is the cross sectional area and L is the length of the material. The units of conductivity are siemens per metere (S m^-1)