UPSC CSE Prelims 2007
Most non-metals are poor conductors of electricity because their electrons are tightly bound and not free to move. However, selenium is an exception. It exhibits photoconductivity, meaning its electrical conductivity increases significantly upon exposure to light. This property makes it valuable in applications such as photocells, solar cells, and light sensors, where its conductivity changes in response to light intensity. Thus, selenium is not classified as a poor conductor of electricity.
Sulphur, Bromine, and Phosphorus are typical non-metals that are poor conductors of electricity. Their valence electrons are localized and not available for conduction, making them effective electrical insulators under normal conditions.