Joseph Henry 1797 - 1878_1

Joseph Henry 1797 - 1878_1 - Joseph Henry a story behind...

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Joseph Henry: a story behind the unit of inductance Henry : Joseph Henry was one of the first great American scientists after Benjamin Franklin. Many parallels exist between his life and work and that of the English physicist Michael Faraday. Like Faraday, Henry was born into a poor family. Both received little formal education and both were apprenticed at an early age, Faraday to a book binder, and Henry to a watchmaker at the age of 13. Both, finally made lasting contributions to the field of electrical research. Henry's interest in science was sparked by an odd coincidence. He had chased his pet rabbit underneath a church. Noticing that some floorboards were missing, 16-year-old Joseph climbed into the church and found a shelf of books. He began looking through Lectures on Experimental Philosophy and was soon hooked on science. He entered the Albany Academy in New York and later began to teach at country schools to earn an income. He graduated from the Academy and was leaning toward studying medicine when a surveying job turned up, and that steered him toward engineering. In 1826 Henry was back at the Albany Academy, but this time as a teacher of mathematics and science. In 1820, Danish physicist Hans Christian Oersted (1777-1851) had discovered that the flow of an electric current produced a magnetic field around the wire. This amazed scientists and many, including Henry and Faraday, began to experiment with magnetism. In 1829 Henry learned that William Sturgeon (1783-1850) had built an electromagnet that could lift nine pounds (4 kg). This was quite remarkable, but Henry believed he could create a magnet that was much stronger. The secret was to wrap more wire around the iron core, overlapping the levels. However, wire in that era was
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