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Hall effect

(Encyclopedia)Hall effect, experiment that shows the sign of the charge carriers in a conductor. In 1879 E. H. Hall discovered that when he placed a metal strip carrying a current in a magnetic field, a voltage dif...

Charles III, emperor of the West, king of the East Franks, and king of the West Franks

(Encyclopedia)Charles III or Charles the Fat, 839–88, emperor of the West (881–87), king of the East Franks (882–87), and king of the West Franks (884–87); son of Louis the German, at whose death he inherit...

Saint Louis

(Encyclopedia)Saint Louis lo͞oˈĭs [key], city (1990 pop. 396,685), independent and in no county, E Mo., on the Mississippi River below the mouth of the Missouri; inc. as a city 1822. St. Louis has long been a ma...

McCormick, Robert Sanderson

(Encyclopedia)McCormick, Robert Sanderson, 1849–1919, American diplomat, b. Rockbridge co., Va.; nephew of Cyrus Hall McCormick. President McKinley appointed (1901) him minister to Austria-Hungary. He became the ...

Browne, Sir Thomas

(Encyclopedia)Browne, Sir Thomas, 1605–82, English author and physician, b. London, educated at Oxford and abroad, knighted (1671) by Charles II. His Religio Medici, in which Browne attempted to reconcile science...

magnetic resonance

(Encyclopedia)magnetic resonance, in physics and chemistry, phenomenon produced by simultaneously applying a steady magnetic field and electromagnetic radiation (usually radio waves) to a sample of atoms and then a...

Putnam, Rufus

(Encyclopedia)Putnam, Rufus, 1738–1824, American Revolutionary general, one of the founders of the Ohio Company of Associates, b. Sutton, Mass.; cousin of Israel Putnam. In the French and Indian War he joined (17...

Robertson, Sir William Robert

(Encyclopedia)Robertson, Sir William Robert, 1860–1933, British field marshal. He enlisted in the army in 1877 and became an officer in 1888. He was in the intelligence department in India (1892–96) and served ...

induction, in electricity and magnetism

(Encyclopedia)induction, in electricity and magnetism, common name for three distinct phenomena. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing ...

harvester

(Encyclopedia)harvester, farm machine that mechanically harvests a crop. Small-grain harvesting has been mechanized to a certain extent since early times. In the modern period the first harvester to gain general ac...