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
Tapis crude allows for greater production of higher-value products, such as petrol, than from Brent or WTI. Its high price is also due to the purity of the blend. Because it contains less sulfur it requires less refinery processing than sourer crude oils such as Brent Oil and WTI. Malaysia is the only country which has significant amounts of oil produced as Tapis, from fields located in the South China Sea. Tapis crude Tapis crude is a Malaysian crude oil used as a pricing benchmark in Singapore. Tapis is very light, with an API gravity of 43°-45°, and very sweet, with only