Electric light be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap. The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric arc through a gas, and LED lamps, which produce light by a flow of electrons across a band gap in a semiconductor. Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, and fires. Cornish chemist Humphry Davy developed the first incandescent light in 1802, followed
Light crude oil of light crude set a new intraday high on May 21, 2008, of $133.45 and closed at $133.17. A new high was reached on July 11, 2008, as prices temporarily reached $147.27 a barrel. Light crude oil is traded on the CME Globex, CME ClearPort, (CME Group) and Open Outcry (New York) futures exchange venues and is quoted in U.S. dollars and cents per barrel. Its product symbol is "CL" and its contract size is with a minimum fluctuation of $0.01 per barrel. Light crude oil Light crude oil is liquid petroleum that has a low density and flows freely