<P> The first demonstrative long distance (34 km, i.e. 21 mi) AC line was built for the 1884 International Exhibition of Turin, Italy . It was powered by a 2 - kV, 130 - Hz Siemens & Halske alternator and featured several Gaulard secondary generators with their primary windings connected in series, which fed incandescent lamps . The system proved the feasibility of AC electric power transmission on long distances . After this success, between 1884 and 1885, Hungarian engineers Zipernowsky, Bláthy, and Déri from the Ganz company in Budapest created the efficient "Z.B.D." closed - core coils, as well as the modern electric distribution system . The three had discovered that all former coreless or open - core devices were incapable of regulating voltage, and were therefore impractical . Their joint patent described two versions of a design with no poles: the "closed - core transformer" and the "shell - core transformer". Ottó Bláthy suggested the use of closed - cores, Károly Zipernowsky the use of shunt connections, and Miksa Déri performed the experiments . </P> <P> In the closed - core transformer the iron core is a closed ring around which the two coils are wound . In the shell type transformer, the windings are passed through the core . In both designs, the magnetic flux linking the primary and secondary windings travels almost entirely within the iron core, with no intentional path through air . The core consists of iron strands or sheets . These revolutionary design elements would finally make it technically and economically feasible to provide electric power for lighting in homes, businesses and public spaces . Zipernowsky, Bláthy and Déri also discovered the transformer formula, Vs / Vp = Ns / Np . Electrical and electronic systems the world over rely on the principles of the original Ganz transformers . The inventors are also credited with the first use of the word "transformer" to describe a device for altering the EMF of an electric current . </P> <P> A very first operative AC line was put into service in 1885 in via dei Cerchi, Rome, Italy, for public lighting . It was powered by two Siemens & Halske alternators rated 30 hp (22 kW), 2 kV at 120 Hz and used 200 series - connected Gaulard 2 - kV / 20 - V step - down transformers provided with a closed magnetic circuit, one for each lamp . Few months later it was followed by the first British AC system, which was put into service at the Grosvenor Gallery, London . It also featured Siemens alternators and 2.4 - kV / 100 - V step - down transformers, one per user, with shunt - connected primaries . </P> <P> The concept that is the basis of modern transmission using inexpensive step up and step down transformers was first implemented by Westinghouse, William Stanley, Jr. and Franklin Leonard Pope in 1886 in Great Barrington, Massachusetts, resorting also to European technology . In 1888 Westinghouse also licensed Nikola Tesla's induction motor patent giving AC a much needed usable motor . This system was developed into the modern 3 - phase system by Mikhail Dolivo - Dobrovolsky and Allgemeine Elektricitäts - Gesellschaft and Charles Eugene Lancelot Brown in Europe, starting in 1889 . The simplicity of polyphase generators and motors meant that besides their efficiency they could be manufactured cheaply, compactly and would require little attention to maintain . Simple economics would drive the expensive, bulky and mechanically complex DC dynamos to their ultimate extinction . As it turned out, the deciding factor in the War of Currents was the availability of low cost step up and step down transformers that meant that all customers regardless of their specialized voltage requirements could be served at minimal cost of conversion . This "universal system" is today regarded as one of the most influential innovations for the use of electricity . </P>

When did it become common to have electricity