Inert gas Inert gas An inert gas/noble gas is a gas which does not undergo chemical reactions under a set of given conditions. The noble gases often do not react with many substances, and were historically referred to as the inert gases. Inert gases are used generally to avoid unwanted chemical reactions degrading a sample. These undesirable chemical reactions are often oxidation and hydrolysis reactions with the oxygen and moisture in air. The term "inert gas" is context-dependent because several of the noble gases can be made to react under certain conditions. Purified argon and nitrogen gases are most commonly used as
Incandescent light bulb 1914, 88.5 million lamps were used, (only 15% with carbon filaments), and by 1945, annual sales of lamps were 795 million (more than 5 lamps per person per year). Of the power consumed by typical incandescent light bulbs, 95% or more is converted into heat rather than visible light. Other electrical light sources are more effective. Luminous "efficacy" of a light source may be defined in two ways. The radiant luminous efficacy (LER) is the ratio of the visible light flux emitted (the "luminous flux") to the total power radiated over all wavelengths. The source luminous efficacy (LES) is the