ignition ballast resistor

[john mcintyre <johnmc@domain.elided>]

  Good day all
                I have been lead to believe, that the ballast resistor
  fitted to ignition system to limit coil primary winding current flow ,
 to about 3 ampere under  most engine speeds to do this the following must
be  allowed for.
   1, Most 12 volt ignition coils are really only 9 volt primary winding coil.
      so when starting engine, battery voltage drops to about 9 volts and the
      ballast resistor is bypassed ,and the coil gets full 9 volts
   
   2, When the engine is running slowly, the and there is a large relative 
      time for the coil current to build up, the ballast resitor heats up
      causing more resistance to current flow  thus limiting the current flow
      in the ignition system.

   3,  At maximum  engine speed, the relative time allowed for the current
to          build up in ignition coil is much reduced ,thus the ballast
resistor 
       hardly heats up this allows more voltage to try and push enough 
       current into the coil for satisfactory ignition. 
    
   4,  Actual ballast resistor resistance varies as the speed of the engine.


        reguards  john