science · 22 December 1799 · 225 years ago
birth
Born 22 Dec 1799; died 10 Jan 1864 at age 64.
Irish physicist who pioneered in electrical science. He invented the induction coil (1836) before that of better-known Heinrich Ruhmkorff. Callan's coil was built using a horseshoe shaped iron bar wound with a secondary coil of thin insulated wire under a separate winding of thick insulated wire as the “primary” coil. Each time a battery's current through the “primary” coil was interrupted, a high voltage current was produced in the electrically separate “secondary” coil. By 1837, Callan used a clock mechanism to rock a wire in and out of a small cup of mercury to interrupt the circuit 20 times/sec on a giant induction machine, producing 15-inch sparks (estimated at 600,000 volts).
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