Scope pics...

[steve ravet]

Bruce Plecan wrote:

> So it goes from A/C to D/C just cause there is an air gap?.
> That doesn't make sense to me.

There's not much disagreement in this thread, except for terminology. 
AC may stand for alternating current, but what it really means is one
that varies with time.  Any voltage that varies with time, even if the
polarity never changes, is still AC.  Even a battery produces AC
voltage, because if you measure it long enough it decays and approaches
zero.  The voltage across a plug certainly varies with time and is
therefore "AC".  It's not a bunch of DCs that all have a different
value.

> 
> Thus the current through the spark plug, which is only
> > >during spark, is always going in the same direction.

This is also true.  What the electrons are doing is the equivalent of
you speeding up and slowing down between 55 and 65.  You never stop
moving forward, only the rate of moving forward changes.  BUT, this is
still AC, not DC.  The effect of the electrons changing velocity (radio
hiss, etc.) is the same whether that change is centered on 0 or 15Kv.

I think every post made in this thread has been basically correct, with
the exception of the first one that claimed that spark voltage is DC. 
There have only been misunderstandings in terminology.  Plus, there's
very little gmecm content here....

> 
> Theory is fine, but when the real world doesn't support it, the theory comes
> into guestion in my book

The "Hitchiker's Guide to the Galaxy" states conclusively "Any
discrepancy between this Guide and reality are clearly the result of a
defective reality".

--steve

-- 
Steve Ravet
steve.ravet at arm.com
ARM,Inc.
www.arm.com
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