Joseph Henry

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Joseph Henry
BirthplaceAlbany, New York, USA
NationalityUnited States
Known for Electromagnetic induction, Inventor of a precursor to the electric doorbell and electric relay

Henry, Joseph,

1797–1878, American physicist, b. Albany, N.Y., educated at Albany Academy. He taught (1826–32) mathematics and natural philosophy at Albany Academy and was professor of natural philosophy (1832–46) at Princeton (then the College of New Jersey). From 1846 he served as the first secretary and director of the newly founded Smithsonian Institution; he introduced and developed many of its activities and established its general policies. Before assuming his responsibilities at the Smithsonian, he had made notable contributions to the physical sciences, especially in electromagnetism. Henry improved the electromagnet, increasing its strength and fitting it for practical use. He invented and operated the first electromagnetic telegraph, which formed the basis for the commercial telegraphic system. He discovered self-inductance, and the unit of inductanceinductance,
quantity that measures the electromagnetic induction of an electric circuit component; it is a property of the component itself rather than of the circuit as a whole.
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 is often called the henry in his honor. Independently of Michael FaradayFaraday, Michael
, 1791–1867, English scientist. The son of a blacksmith, he was apprenticed to a bookbinder at the age of 14. He had little formal education, but acquired a store of scientific knowledge through reading and by attending educational lectures including, in
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, he discovered the principle of the induced current, basic to the dynamo, transformer, and many other devices. Henry invented a small electromagnetic motor, and extended the work on induced currents to show that an induced current can be used to induce another current in a nearby circuit and that resulting currents in turn can induce others. His numerous other contributions include the institution of the weather report system.


See his Papers, ed. by N. Reingold et al. (15 vol., 1972–); biographies by S. R. Riedman (1961) and A. E. Moyer (1997).

Henry, Joseph


Born Dec. 17, 1797, in Albany, N. Y.; died May 13, 1878, in Washington, D. C. American physicist.

In 1832, Henry was appointed a professor at the College of New Jersey (now Princeton University). From 1846 he served as secretary and director of the Smithsonian Institution. In 1868 he was appointed president of the National Academy of Sciences, and in 1871 he became the first president of the Philosophical Society of Washington. His principal works were devoted to electrical engineering. In 1828, Henry built the first high-powered electromagnets using multilayered coils of insulated wire. He discovered the phenomenon of self-induction (1832) and the oscillatory character of the capacitor discharge (1842). The unit of inductance in the International System of Units—the henry—has been named after him. Henry also wrote works in meteorology.


Scientific Writings, vols. 1-2, Washington, 1886.


Lebedev, V. I. “Izobretenie Dzhozefa Genri.” Vestnik sviazi, 1946, no. 8.

Henry, Joseph

(1797–1898) physicist; born in Albany, N.Y. He worked as a tutor, then as a surveyor (1825–26) before becoming a professor at his alma mater, Albany Academy (1826–32). He began research on electromagnetism (1827), constructed the first electromagnetic motor (1829), and discovered electrical induction independent of English physicist Michael Faraday. The "henry" unit of inductance is named after him. He continued his research after transferring to Princeton (1832–46), demonstrating the oscillatory nature of electrical discharges (1842), and diversifying into the fields of astronomy, galvanometry, and telegraphy. In 1846 he was named first secretary and director of the Smithsonian Institution; through his leadership (1846–77), the Smithsonian supported internationally cooperative scientific research. While administrative duties left him little time for the "pure" scientific endeavors he favored, Henry introduced a system of weather forecasting, investigated the propagation of light and sound waves by lighthouses, and encouraged the museum's patronage of anthropology and ethnology.