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1831年10月的一天,英国皇家学会的科学会堂座无虚席。一位刚过“不惑之年”的中年科学家站在讲桌旁,熟练地表演一个小试验,数以千计的观众目不转睛地望着讲桌上。科学家手里拿着一个连接电流表的小线圈和一根条形磁铁。他把磁铁放在手里不动,观众们看到电流表的指针不动,线圈中没有电流。他从容地把磁铁插入线圈,观众们清楚地看到电流表的指针向右偏转,线圈中产生了电流。他又把磁铁从线圈中拿出来,观众们又看到电流表的指针向左偏转,线圈中产生了相反方向的电流。至此,科学家向在座的观众公开宣布:磁能产生电!
One day in October 1831, the Royal Society’s Science Hall was packed. A middle-aged scientist who had just passed the age of perplexity stood at the table, skillfully performed a small experiment, and thousands of spectators stared intently at the table. The scientist holds a small coil with ammeter in the hand and a bar magnet. He put the magnet in his hand and the audience saw that the pointer of the ammeter did not move and there was no current in the coil. He slidly inserted the magnet into the coil, and the audience clearly saw the pointer of the ammeter deflecting to the right, creating a current in the coil. He took the magnet out of the coil again, and the audience saw the ammeter’s pointer deflect leftward, producing a reverse current in the coil. At this point, scientists publicly declared to the audience here: magnetic energy generated electricity!