Electrical Instrumentation, 1800-1820
The 20 years following the announcement of the voltaic-pile invention were years of intense experimental activity with this device. Many new chemical elements were discovered, beginnings were made on the electrochemical series of the elements, the electric arc and incandescent platinum wires suggested the possibilities of electric lighting, and various electrochemical observations gave promise of other practical applications such as metal-refining, electroplating, and quantity production of certain gases. Investigators were keenly aware that all of the available means for measuring and comparing the electrical aspects of their experiments (however vaguely these “electrical aspects” may have been conceived), were slow, awkward, imprecise, and unreliable.
The atmosphere was such that prominent scientists everywhere were ready to pounce immediately on any reported discovery of a new electrical “effect,” to explore its potentialities for instrumental purposes. Into this receptive environment came H. C. Oersted’s announcement of the magnetic effects of a voltaic circuit, on July 21, 1820. [9]
Figure 2.—“Galvanometer” was the name given by Bischof to this goldleaf electrostatic instrument in 1802, 18 years before Ampère coupled the word with the use of Oersted’s electromagnetic experiment as an indicating device.
Many writers have expressed surprise that with all the use made of voltaic cells after 1800, including the enormous cells that produced the electric arc and vaporized wires, no one for 20 years happened to see a deflection of any of the inevitable nearby compass needles, which were a basic component of the scientific apparatus kept by any experimenter at this time. Yet so it happened. The surprise is still greater when one realizes that many of the contemporary natural philosophers were firmly persuaded, even in the absence of positive evidence, that there must be a connection between electricity and magnetism. Oersted himself held this latter opinion, and had been seeking electromagnetic relationships more or less deliberately for several years before he made his decisive observations.
His familiarity with the subject was such that he fully appreciated the immense importance of his discovery. This accounts for his employing a rather uncommon method of publication. Instead of submitting a letter to a scientific society or a report to the editor of a journal, he had privately printed a four-page pamphlet describing his results. This, he forwarded simultaneously to the learned societies and outstanding scientists all over Europe. Written in Latin, the paper was published in various journals in English, French, German, Italian and Danish during the next few weeks.[10]
In summary, he reported that a compass needle experienced deviations when placed near a wire connecting the terminals of a voltaic battery. He described fully how the direction and magnitude of the needle deflections varied with the relative position of the wire, and the polarity of the battery, and stated “From the preceding facts, we may likewise collect that this conflict performs circles….” Oersted’s comment that the voltaic apparatus used should “be strong enough to heat a metallic wire red hot” does not excuse the 20-year delay of the discovery.