They discovered the phenomenon of electromagnetic induction.
Joseph Henry (1797-1878), American scientist. He is a great physicist named after the unit of inductance "Henry". He has made outstanding contributions to electrical science. He invented the relay (the prototype of the telegraph), discovered the phenomenon of electromagnetic induction earlier than Faraday, and also discovered the principle of automatic electronic ignition. But he didn’t apply for a patent in time. He is considered one of the greatest American scientists after Benjamin Franklin and has made great contributions to electromagnetism.
①The making of strong electromagnets laid the foundation for improving generators
In 1827, he used yarn-wrapped copper wire to wrap two layers around an iron core, and then wrapped it in copper When electricity was applied to the wire, it was found that the iron core, which weighed only 3 kilograms, actually attracted an iron block weighing 300 kilograms, far exceeding the attraction of ordinary natural magnets. The transformation of electricity into magnetism produced such a powerful force that immediately attracted Henry to continue exploring these electromagnetic phenomena. In 1829, Henry improved the electromagnet invented by the British inventor William Sturgeon (1783-1850). He wrapped the wires in silk instead of Sturgeon's bare wires to insulate the wires from each other and outside the iron block. It is wrapped in several layers to greatly enhance the attraction of the electromagnet. Later, he made a small electromagnet that could lift an iron block weighing one ton.
② The phenomenon of electromagnetic induction was discovered one year earlier than Faraday
In August 1830, Henry placed a strip of soft iron rod wrapped with a wire between the two poles of the electromagnet. Then connect the wires on the bar-shaped iron rod to the galvanometer to form a closed loop. He observed that when the wire of the electromagnet was connected, the pointer of the galvanometer deflected to one side and then returned to zero; when the wire was disconnected, the pointer deflected to the other side and returned to zero. This is the phenomenon of electromagnetic induction discovered by Henry. This was one year before Faraday discovered the phenomenon of electromagnetic induction. However, at that time, the center of world science was in Europe, and Henry was concentrating on making larger electromagnets and did not publish the experimental results in time. Therefore, the credit for discovering the electromagnetic induction phenomenon belongs to Faraday, who published the results in time, and Henry lost Invention rights.
③Discovered the phenomenon of self-induction
Henry conducted comparative experiments on the lifting forces of various electromagnets wound with wires of different lengths. He unexpectedly discovered that sparks were generated when the coil carrying current was disconnected. In August of the next year, Henry conducted another study on this phenomenon. In 1832, he published the paper "Electric Self-Induction in Long Spirals", announcing the discovery of the phenomenon of electric self-induction. In 1837, Henry visited Europe and spent many days happily with Faraday. Faraday wanted to do a simple experiment to make a thermocouple produce sparks. He placed one end of the electric couple on a hot stove, buried the other end in ice, and touched the ends of the two leads, but it did not produce the expected results. At this time, Henry wound a wire into a coil and put it on an iron rod. He connected the coil to a lead of the thermocouple, and then made the two wire ends touch each other, and a dazzling spark suddenly exploded. . Faraday greatly appreciated this experiment and asked loudly: "How did you succeed?" So Henry had to explain the principle of self-induction to this scientist who was famous for publishing the laws of electromagnetic induction. Obviously, there was no one at that time. Europeans read the papers Henry had published years earlier. In 1832, when he was developing an electromagnet with stronger attraction, he discovered that an electric spark was generated when the energized coil wrapped with an iron core disconnected the circuit. This is the phenomenon of self-induction. After repeated experiments, he figured out the rules that produced this phenomenon, and published a paper explaining the self-induction phenomenon in 1835.