The substances by which electricity or charges flow is called medium. It is classified into three types are
(iii) Non conductor
(i) Conductor: conductor is this substance in which electricity or charges can flow easily. Examples of conductors are copper, gold, iron etc metal, human body, acids, bases etc. through these substances charges can flow easily so they are conductors. Electrical conductivity of electricity conductors are also depends upon temperature. Conductivity of conductor in electricity decreases when temperature increases and conductivity increases when temperature decreases.
(ii) Semiconductor: Those substances are called semi conductor through which charge can flow partially. Germanium, arsenic, silicon etc are the examples of semi conductors. In present semi conductors are used hugely in making electronic instruments. Conductivity of semiconductor increases by increasing temperature.
(iii)Non conductor or insulator: Non conductor or insulator is that substance through which charge does not flow. Rubber, glass, ebonite, dry wood etc are insulators. Charge cannot flow through the non conductor material in normal temperature. Plastic is great electric insulator so it is used with wire as cover as human body remains safe touching with the electric supplying wire. Electrical wire is the combination of insulators and conductors.