[urq] ignition system electrical question

[Justin]

It really just the concept of a ground. A ground just means 0 volts. The
battery and all electrical components are at 12 volts higher than this
ground. It's possible to have components at higher than 12 volts
(coil,..etc.) above this common ground. (It's like the concept of gravity,
it's possible to have a hills or a cliffs higher than each other, but both
end at the same level..."ground", even though the higher cliff or hill is at
a higher potential energy than the other....)

Just to peak your curiosity, it takes a electric field of about 3x10^8 N/C
to cause a spark in air...(ionization of air...), that's why the voltage out
the coil is so high...

Hope this helps,

Justin

----- Original Message -----
From: "Mike Fitton" <rfitton at vt.edu>
To: "urq list" <urq at audifans.com>
Sent: Monday, March 29, 2004 10:21 PM
Subject: [urq] ignition system electrical question


> No Audi-specific content here, but something's been bothering me lately.
>   Okay, the coil generates a spark that's like 50 billion volts or
> something (or at least a lot more than 12) and sends that out, through
> the distributor, through the plug wires, through the plug.  I kind of
> understand where this voltage comes from...the sudden collapse of a
> magnetic field in the coil which creates something that probably has a
> much more technical term but is essentially an electrical whiplash...the
> same sort of thing that relays without diodes can do that destroys
> switches over time.  Now, what I don't get is where this voltage goes
> after the spark plug.  It seems like it would just ground to the engine
> and then eventually the battery.  But how can this kind of voltage
> ground to a 12v negative?  BTW, anyone know exactly how much voltage and
> current is actually taking place here?
>
> -Cheers!
> Mike
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