Power in an electric circuit is the rate of flow of energy past a given point of the circuit.
The portion of power that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as active power (sometimes also called real power).
The portion of power due to stored energy, which returns to the source in each cycle, is known as reactive power.Źródło: https://en.wikipedia.org/wiki/AC_power
Although electricity had been known to be produced as a result of the chemical reactions that take place in an electrolytic cell since Alessandro Volta developed the voltaic pile in 1800, its production by this means was, and still is, expensive. In 1831, Michael Faraday devised a machine that generated electricity from rotary motion, but it took almost 50 years for the technology to reach a commercially viable stage. In 1878, in the US, Thomas Edison developed and sold a commercially viable replacement for gas lighting and heating using locally generated and distributed direct current electricity. The world's first public electricity supply was provided in late 1881, when the streets of the Surrey town of Godalming in the UK were lit with electric light. This system was powered from a water wheel on the River Wey, which drove a Siemens alternator that supplied a number of arc lamps within the town..This supply scheme also provided electricity to a number of shops and premises to light 34 incandescent Swan light bulbs. Additionally, Robert Hammond, in December 1881, demonstrated the new electric light in the Sussex town of Brighton in the UK for a trial period.
The ensuing success of this installation enabled Hammond to put this venture on both a commercial and legal footing, as a number of shop owners wanted to use the new electric light.
Thus the Hammond Electricity Supply Co.
was launched.Whilst the Godalming and Holborn Viaduct Schemes closed after a few years the Brighton Scheme continued on, and supply was in 1887 made available for 24 hours per day. In early 1882, Edison opened the world?s first steam-powered electricity generating station at Holborn Viaduct in London, where he had entered into an agreement with the City Corporation for a period of three months to provide street lighting.In time he had supplied a number of local consumers with electric light.The method of supply was direct current (DC).Źródło: https://en.wikipedia.org/wiki/Electric_power_industry#History