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  3. The electromagnet was invented in England by William Sturgeon, who took an i

The electromagnet was invented in England by William Sturgeon, who took an i

游客2025-03-21  27
问题     The electromagnet was invented in England by William Sturgeon, who took an iron rod and bent it into the shape of a horseshoe. This "horseshoe" was coated with varnish (清漆) and a layer of copper wire was wrapped around it. An electric current was passed through the wire, thus making the rod magnetic. The rod was now, because of magnetic attraction, able to support nine pound of iron.
    In the US, a scientist named Joseph Henry improved on Sturgeon’s electromagnet by insulating (使绝缘) the copper wire with silk. He was able to wrap many turns of wire around an iron core without danger of circuits between the turns. His magnet could hold 2 300 pounds.
    This experiment prompted Henry to try his hand at converting magnetism into electricity. First he coiled (缠绕, 盘绕) some insulated wire around an iron bar, connecting both ends of the wire to a galvanometer (电流计). The iron bar was placed across the poles of the electromagnet. Then the coil of the electromagnet was connected to a battery. The galvanometer indicated a voltage , then dropped to zero. Henry signaled his assistant to disconnect the coil. The galvanometer showed that once again a voltage had been produced, although this time in the opposite direction. The principle of electromagnet induction (感应现象) had thus been discovered. Unfortunately for Joseph Henry he did not publish findings and someone else (Faraday) got the credit for the discovery. [br] According to what appeared in print at that time______.
选项 A、Joseph Henry discovered the principle of electromagnetic induction
B、Henry falsely tried to claim credit for the discovery of the principle of electromagnetic induction
C、Faraday discovered the principle of electromagnetic induction
D、Henry’s experiment with electromagnetic induction was a failure
答案 C
解析 本题问按照当时发表的文字记载，是谁发现了电磁感应定律。根据文章内容我们知道，事实上是亨利发现了电磁感应定律。不幸的是，亨利没有公开发表他的成果，而被他人(法拉第)得到了这项发现的荣誉。因此，本题的正确答案应是c“按照当时的公开发表的文字记载是法拉第发现了电磁感应定律”。
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