The electric conductivity of substances and life application on it
The electric conductivity
The substances can be classified according to the electric conductivity into good conductors of electricity and bad conductors of electricity , The electrical conductivity is the ability of a material to carry the flow of an electric current ( a flow of electrons ) .
Good conductors of electricity are able to carry a complete electric current in end to end voltage such as copper , gold , silver , aluminium , …….etc , and there are some conductors that are not metals . Carbon is the best example .
Bad conductors of electricity are the substances do not allow electricity to flow through such as the gases , some solutions as solution of hydrogen chloride in benzene , sugary solution , some solid elements as sulphur , phosphorus , the wood and the plastic .
The insulators are materials which are bad conductors of electricity , they have high resistivity because they have no charge carriers or free electrons to carry the electric current such as the glass , the rubber .
Some materials cannot be classified as either conductors or insulators , They are the semiconductors , They are the materials that conduct an electric current but they do very poorly .
The semiconductors act as good conductors under some conditions and poor conductors under other conditions such as silicon , germanium, and various metal oxides .
The semiconductors are materials whose conductivities lie between the conductors and the insulators , when the temperature of a semiconductor is increased its resistivity decreases or conductivity increases .
At higher temperature , The semiconductors conducts better , therefore the semiconductor have negative temperature coefficient of resistance .
Life application on electric conductivity
The electric wires ( or the cables ) are made of copper or aluminium and covered by a plastic layer because both of copper and aluminium are good conductors of electricity , while the plastic is a bad conductor of electricity .
The screwdrivers are made of steel iron , while their handles are made of the wood or the plastic because steel iron is good conductor of electricity , but the wood and the plastic are bad conductors of electricity .