(i) Graphite is a non-metallic conductor of electricity 1 so is cheap, insoluble in water, acids and bases; and is non-corrosive material. Due to these properties, it is used in making electrodes.
(ii) Polyvinyl Chloride (PVC) or a rubber-like material are insulators and hence do not allow electrons to flow. Hence, these are used in coating the electrical wires.
(iii) Metals and metal alloys are generally sonorous in nature, i.e. they produce sound. Due to this property, they are used for making bells and strings of musical instruments.