LARGE 18 INCH INDUCTION COIL, or RUHMKORFF COIL, 1900's

Originally used for powering the X-Ray tube (Item A0198 and Screen A0199) Electromagnetic induction was discovered by Michael Faraday (1791-1867) in 1831. Nicolas Callan (1799-1864) invented the induction coil in 1836. They were used for medical complaints such as skin disorders and to power X Ray machines. Marconi used one for his experiments prior to developing his transmitter system for the first transatlantic transmission from Poldhu in Cornwall. Also they were used in Spark Transmitters for the next 30 years.
The coil section of this unit measures 18 inches.
They work by two coils, one with a smaller number of turns but of greater size of wire, surrounded by another of much greater turns but of smaller diameter wire, inside the centre winding is a core of iron at the end of which is a piece of metal, attached to a make and break contact which interrupts the supply to the centre winding, exactly as in an electric bell. The result is a transfer of power from the centre winding to the outer, with a proportional change in voltage to the number of turns, i.e. from a small voltage you can create a very high voltage, but at much lower current.

Your comments:

• Marconi at Poldhu used a transmitter specially designed by Prof. J Ambrose Fleming. This consisted of a 2kv alternator and transformers to power the spark gap - and much more besides.... !
  .......... Dr Anthony Constable, Ealing, London, 29th of October 2010
  
  

A0136