Chris,
Coils are polarized to cause the high voltage delivered to the
distributor/plugs to be negative with respect to the car ground.
(regardless of whether the car is + or - ground)
The "-" voltage at the plugs produces a bigger spark event than "+"
all other things being equal. This is due to "thermionic emission"
i.e. the propensity of free electrons to more easily "jump" from
certain metals when they are heated. The center electrode of a
spark plug runs at a higher temperature than the outer one.
Chris Amley wrote:
>
> Hi -- I've been off the list for a while and I hope this hasn't been
> recently covered, but...why do ignition coils have polarity?
[...]
--
Bob Sykes
"You can't beat your brains for entertainment."
|