Gallium arsenide (GaAs) Crystalline form of gallium and arsenic, which yields high-efﬁciency solar cells.
Galvanic cell See: Electrochemical cell
Gamma radiation Form of radiant energy consisting of high-energy particles of light. See also: Ionizing radiation
Gas 1. Fuel gas, such as natural gas, undiluted liqueﬁed petroleum gases (vapor phase only), liqueﬁed petroleum gas-air mixtures, or mixtures of these gases. Combustion of these gases produces CO2 and H2O. CO2 is a major contributor to greenhouse gas.