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McMahon, Brien

(Encyclopedia)McMahon, Brien (James O'Brien McMahon), 1903–52, American statesman, b. Norwalk, Conn. After practicing law, he became a judge in Norwalk, and from 1933 to 1936 he served in the office of the U.S. A...

power, in physics

(Encyclopedia)power, in physics, time rate of doing work or of producing or expending energy. The unit of power based on the English units of measurement is the horsepower, devised for describing mechanical power b...

quantum theory

(Encyclopedia)quantum theory, modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity togethe...

Fowler, William Alfred

(Encyclopedia)Fowler, William Alfred, 1911–95, American nuclear astrophysicist, b. Pittsburgh. While a professor at the California Institute of Technology, Fowler studied how chemical elements are formed in nucle...

Heisenberg, Werner

(Encyclopedia)Heisenberg, Werner vĕrˈnər hīˈzənbĕrk [key], 1901–76, German physicist. One of the founders of the quantum theory, he is best known for his uncertainty principle, or indeterminacy principle, ...

prime mover

(Encyclopedia)prime mover: see energy, sources of. ...

Lenz's law

(Encyclopedia)Lenz's law, physical law, discovered by the German scientist H. F. E. Lenz in 1834, that states that the electromotive force (emf) induced in a conductor moving perpendicular to a magnetic field tends...

photoelectric effect

(Encyclopedia)photoelectric effect, emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory ...

phosphorylation

(Encyclopedia)phosphorylation, chemical process in which a phosphate group is added to an organic molecule. In living cells phosphorylation is associated with respiration, which takes place in the cell's mitochondr...

Strategic Air Command

(Encyclopedia)Strategic Air Command (SAC), former command of the U.S. air force (see Air Force, United States Department of the) charged with organizing, training, equipping, administering, and preparing strategic ...