Rhumkorff's Coil- spark coil 6V-9V.DC operation

The Rhumkorff Coil is a trembler type spark coil. A primary coil of few turns of heavy wire is wound on an iron core and is fed by pulses of DC current. This coil is mounted horizontally  so that another larger diameter coil can be slid over the outside of it. The iron core attracts an armature which breaks a contact that feeds the current into the primary coil. When the current is interrupted  and the magnetic field collaspes, the armature returns to make electrical contact again and current flows in the primary coil again. Thus the armature oscillates or vibrates and the current through the primary coil is switched on and off very quickly as the contacts on the armature rapidly open and close.In the case of the Rhumkorff coil the magnetic field  is being switched on and off very suddenly  so that the magnetic field collaspes almost instantly and this means that the rate of change of magnetic field is extremely high. Because of this high rate,the highly insulated secondary coil develops a very high voltage of around 50,000 volts.