transformers

[eric schumacher]

HI
This is a supplement to Backyard Bob's explanation. With ignition coils you
do better to think of them as inductors. The low tension side charges the
iron and when current flow in it stops the field collapses generating a
voltage in both windings in porportion to the number of turns in each. The
polarity on the coil is marked such that the center electrode on the spark
plug is negative. Since this electrode is gets much hotter than the ground
side it is eaiser for the spark to jump. The correctness of the coil
polarity can be checked with a pencil lead placed in a gap in the HT lead.
There will be a flare on the ground side of the pencil lead on the ground
side of the arc when the polarity is correct. The electrons pull some
graphite with them when they leave the lead.

LAt 10:27 PM 5/28/98 -0500, you wrote:
>> 
>> This might seem off the wall but,   If one side of the coil's secondary
>> is open (point side), and the other side is connected to a spark
>> plug, how is there any flow of electrons with the one side open?.
>> 
>> With the one side open, but yet connected thru the coil to the+ side
>> does that make the return path?.  
>> 
>One side of the secondary goes to the plug, the other side is tied to
>the side of the primary that is connected to the points. The other side
>of the primary is connected to the battery. When the points open there
>is a current loop from ground through the battery, coil primary, coil
>secondary, plug gap, and back to ground. The primary is phased so that
>the voltage generated across it by the collapsing field (300-400 volts)
>is added to the secondary voltage. This is why coils have polarity
>marked on them. If you connect it backwards you lose almost a kilovolt.
>This also means that there is at least 12 volts across the plug gap
>while the points are open.
>-- 
>Robert W. Hughes (Bob)
>BackYard Engineering
>Houston, Texas
>rwhughe at hal-pc.org
>