ABSTRACT
Switching off the primary current by opening the contact breaker points has two major effects which are caused by the collapsing inwards of the magnetic field. These two effects are:
1. Self induction – a voltage of approximately 250 volts is generated across the ends of the primary winding. The direction of this induced voltage in the primary winding is such that it opposes the change which produced it, that is to say that it attempts to maintain the same direction of current flow.
