ABSTRACT
In 1831 Michael Faraday succeeded in producing electricity by plunging a bar magnet into a coil of wire. In the UK electricity is produced at power generating stations at 25 kilovolt potential, in three-phase supply at 50 cycles per second or hertz. A transformer is basically two electric windings, magnetically interlinked by an iron core. An alternating electromotive force applied to one of the windings produces an electromagnetic induction corresponding to an electromotive force in the other winding. Whatever earth method used, a low resistance to an electrical fault is essential. Metal sheathed and armoured cables, earthed metal trunking, metal service pipework associated with electrical equipment and fixed structural steelwork liable to introduce a potential to be protective earthed by bonding together and connecting to earth. Electrical installations must be protected from current overload, otherwise appliances, cables and people using the equipment could be damaged.
