=== Electric light ===
[[Պատկեր:Edison_bulb.jpg|մինի|Thomas Edison's first successful light bulb model, used in public demonstration at Menlo Park, December 1879]]
=== War of currents ===
[[Պատկեր:PyramidParthenon.jpg|մինի|Extravagant displays of electric lights quickly became a feature of public events, as in this picture from the 1897 [[Tennessee Centennial Exposition]].]]
As Edison expanded his [[direct current]] (DC) power delivery system, he received stiff competition from companies installing [[alternating current]] (AC) systems. From the early 1880s AC [[Arc lamp|arc lighting]] systems for streets and large spaces had been an expanding business in the US. With the development of [[Transformer|transformers]] in Europe and by [[Westinghouse Electric (1886)|Westinghouse Electric]] in the US in 1885–1886, it became possible to transmit AC long distances over thinner and cheaper wires, and "step down" the voltage at the destination for distribution to users. This allowed AC to be used in street lighting and in lighting for small business and domestic customers, the market Edison's patented low voltage DC incandescent lamp system was designed to supply.<ref>Jill Jonnes, Empires Of Light: Edison, Tesla, Westinghouse, And The Race To Electrify The World, Random House – 2004, pp. 54–60</ref> Edison's DC empire suffered from one of its chief drawbacks: it was suitable only for the high density of customers found in large cities. Edison's DC plants could not deliver electricity to customers more than one mile from the plant, and left a patchwork of unsupplied customers between plants. Small cities and rural areas could not afford an Edison style system at all, leaving a large part of the market without electrical service. AC companies expanded into this gap.
* [[Francis Robbins Upton]] – mathematician/physicist, joined Menlo Park 1878
* [[Theo Wangemann]] – personal assistant to Edison
== References ==