Editing Locomotive (section)

====Direct current====
[[File:First electric locomotive, built in 1879 by Werner von Siemens.jpg|thumb|Werner von Siemens experimental DC electric train, 1879]]
[[File:B-and-O electric.jpg|thumb|Baltimore & Ohio electric engine, 1895]]

The earliest systems were [[Direct current|DC]] systems. The first electric passenger train was presented by [[Werner von Siemens]] at [[Berlin]] in 1879. The locomotive was driven by a 2.2&nbsp;kW, series-wound motor, and the train, consisting of the locomotive and three cars, reached a speed of 13&nbsp;km/h. During four months, the train carried 90,000 passengers on a {{convert|300|m|ft|adj=mid|-long|abbr=off|sp=us}} circular track. The electricity (150 V DC) was supplied through a third insulated rail between the tracks. A contact roller was used to collect the electricity. The world's first electric tram line opened in Lichterfelde near Berlin, Germany, in 1881. It was built by Werner von Siemens (see [[Gross-Lichterfelde Tramway]] and [[Trams in Berlin|Berlin Straßenbahn]]). The [[Volk's Electric Railway]] opened in 1883 in Brighton, and is the oldest surviving electric railway. Also in 1883, [[Mödling and Hinterbrühl Tram]] opened near Vienna in Austria. It was the first in the world in regular service powered from an overhead line. Five years later, in the U.S. electric [[Tram|trolleys]] were pioneered in 1888 on the [[Richmond Union Passenger Railway]], using equipment designed by [[Frank J. Sprague]].<ref>{{cite web|url=http://www.ieee.org/web/aboutus/history_center/richmond.html|title=Richmond Union Passenger Railway|publisher=[[Institute of Electrical and Electronics Engineers|IEEE History Center]]|access-date=18 January 2008|archive-url=https://web.archive.org/web/20081201032737/http://www.ieee.org/web/aboutus/history_center/richmond.html|archive-date=1 December 2008|url-status=dead}}</ref>

The first electrically worked [[Rapid transit|underground]] line was the [[City & South London Railway]], prompted by a clause in its enabling act prohibiting use of steam power.<ref>{{cite book | last = Badsey-Ellis | first =Antony | title =London's Lost Tube Schemes | publisher = Capital Transport | year = 2005 | location = Harrow | page = 36 | isbn = 1-85414-293-3 }}</ref> It opened in 1890, using electric locomotives built by [[Mather & Platt]]. Electricity quickly became the power supply of choice for subways, abetted by the Sprague's invention of [[multiple-unit train control]] in 1897.

The first use of electrification on a main line was on a four-mile stretch of the [[Baltimore Belt Line]] of the [[Baltimore & Ohio]] (B&O) in 1895 connecting the main portion of the B&O to the new line to New York through a series of tunnels around the edges of Baltimore's downtown. Three [[UIC classification of locomotive axle arrangements|Bo+Bo]] units were initially used, at the south end of the electrified section; they coupled onto the locomotive and train and pulled it through the tunnels.<ref>''B&O Power'', Sagle, Lawrence, Alvin Stauffer</ref>

DC was used on earlier systems. These systems were gradually replaced by AC. Today, almost all main-line railways use AC systems. DC systems are confined mostly to urban transit such as metro systems, light rail and trams, where power requirement is less.