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The induction coil

The induction coil is a piece of apparatus used to produce very high voltages from a low voltage d.c. supply.

When the switch (S) is closed a current flows through the primary coil this magnetises the soft iron rods in the core of the coil. These then attract the soft iron armature(A) which therefore breaks the contact at C. The primary current falls to zero very quickly. This sudden drop in current induces a large voltage in the secondary coil that has a large number of turns. As soon as the contact is broken the magnetic field of the rods disappears, the armature springs back and makes the contact at C once again. The process then repeats itself.

Voltages of many tens of thousands of volts can be made from a 6- 12 V input.

© Keith Gibbs 2011