Leopoldo Nobili: His Galvanometer and His Connections to the Faraday-Neuman-Lenz Law of Induction

The discovery of the phenomenon of magnetic induction, or the Faraday-Neumann-Lenz law of induction, was something much expected, after Hans Christian Ørsted [Rudk⊘bing, Benmark, August 14, 1777 - Copenaghen, Denmark, March 9, 1851] discovered that electric currents had an effect on a magnetic needle. Many researchers, among whom the most notable was Michael Faraday [Southwark, London, UK, September 22, 1791 — Hampton Court, Middlesex, UK, August 25, 1867], actively sought such a phenomenon, yet the instrumentation then available was exceedingly crude [1]. For an electric phenomenon to be apparent, a spark should be o bserved for voltage, or a current strong enough for visible effects. Some more-sensitive device able to detect feeble currents was necessary. Indeed, Orsted's discovery made possible the development of such an instrument: the galvanometer. In that same 1820, Johann Schweigger [Erlangen, Germany, April 8, 1779 - Halle, Germany, September 6, 1857] build a first galvanometer by winding a coil of wire around a magnetic needle free to rotate. This was later enhanced by multiplying the effect of the current by using several coils of wire.