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Joseph HenryAmerican physicist
Date of Birth: 17.12.1797
Country:  USA |
Content:
Biography of Joseph Henry
Joseph Henry, an American physicist, was born in a poor family near Albany, New York. He started off as a farm laborer and later became an apprentice in a shop. At the age of 15, he moved to Albany and worked in a theater for two years. It was by chance that he came across a physics book, which sparked his interest in the subject. He managed to enroll in the Albany Academy and worked as a teacher in a school while studying. He then became an assistant to a chemistry professor, where he demonstrated experiments during public lectures.
Early Discoveries
After graduating from the Academy in 1822, Henry worked as an inspector on the Erie Canal. He later obtained a position as a mathematics and physics teacher in Albany. During the summer, he transformed one of his classrooms into a laboratory and began experimenting with electromagnetism. In 1828, he constructed a powerful horseshoe-shaped electromagnet with a multi-layered coil, capable of lifting a one-ton load. These experiments with electromagnets led him to the idea of generating electricity using magnetic fields. In 1831, he made the discovery of electromagnetic induction. Unbeknownst to Henry, the English physicist Michael Faraday was conducting similar experiments during the same period. Faraday published his results in February 1832, while Henry's first article on the same discovery was published in July of that same year.
Contributions and Achievements
During his time in Albany, Joseph Henry made two other important scientific achievements. He discovered the phenomenon of self-induction in 1831, although his article on this topic was not published until 1838. He also invented the electric relay and electromagnetic telegraph, beating Morse by six years. The telegraph operated on the grounds of Princeton College and transmitted signals over a distance of one mile. In 1832, Henry became a professor at Princeton College (now Princeton University), and in 1846, he became the director of the Smithsonian Institution in Washington, D.C. During this time, he conducted research on the relationship between induced currents. He studied the dependence of mutual induction on the distance between coils and demonstrated that by choosing the appropriate number of turns in the windings, voltage could be increased or decreased (the principle behind modern transformers). In 1842, Henry made a significant discovery when he observed that iron rods in the basement of a building were magnetized by an electrical spark generated on the second floor.
Legacy
Joseph Henry was considered one of the first 50 outstanding scientists elected to the National Academy of Sciences by President Lincoln in 1863. He served as its president from 1868 until his death. The unit of measurement for inductance is named after him. Joseph Henry passed away in Washington, D.C., on May 13, 1878. His contributions to the field of electromagnetism and his pioneering work in the study of induced currents laid the foundation for future developments in the field, which were later described by James Clerk Maxwell's four equations of electrodynamics.
