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 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 about 0.04% sulfur. While it is not traded on a market like Brent Crude or West Texas Intermediate (WTI), it is often used as an oil marker for Asia and Australia. The price of Tapis in Singapore is often considerably higher than the price of benchmark crude oils such as Brent or WTI (those commonly referenced in market commentaries). This is because its greater aromaticity (i.e. higher ° API)