SM091     Inductorium- Ruhmkorff’s coil     circa 1930     Electricity

  This apparatus, capable of producing induced currents at high potentials, consists of a primary coil of wire around a soft iron core.   There is also a make and break device so that the primary current is interrupted regularly.   A secondary coil is wound on top of the primary with precautions as to the insulation of the extremely high potential secondary circuit from that of the low voltage primary.

  The high potential output is produced by induction due to the lines of force of the magnetic field cutting the primary and secondary coils.

  Fizeau increased the output e.m.f. by connecting a condenser in the primary circuit effectively tuning it.

  A commutator is normally included to reverse the direction of the current.

  Another form of current breaker is Wehnelt’s electrolytic interruptor consisting of a platinum anode and a lead cathode dipping in sulphuric acid solution.  

  Heinrich Daniel Ruhmkorff 1803 to 1877 (Portrait circa 1850).