In a message dated 98-08-18 16:06:49 EDT, barneymg@ntsource.com writes:
> As there is a current flowing from the secondary winding across the spark
> plug to ground, what path do you ascribe to that current for it to return
> to the other side of the secondary winding to complete the circuit? This
> was the basic question from the beginning.
Barney,
I don't know. I really don't know. As you said, this is the question that has
been bugging me from the start. If you can bear with me for one more
go-'round, let me describe the circuit, and current flow, as I see it, and
tell me what you think. I'll make it short. I'm using the diagram you posted
on your web page as a reference.
Prior to the opening of the points, electrons are flowing from the negative
post of the battery, through ground, through the points, through the primary,
and then back to the battery positive post. When the points open, the coil
tries to maintain electron flow in the same direction as before. Now, however,
instead of flowing through the points, electrons pile up on the ground side of
the capacitor, leave from the other side, and flow through the primary to the
battery just as before. Current will decay as the capacitor charges. Until the
primary current flow drops to zero, we will have current flow through the
battery.
Sometime during the decay, but before the primary current drops to zero, the
plug will fire. When it does, electrons will leave the high tension post of
the coil secondary - this post being negative with respect to ground - flow
through the tip of the plug, jump to the electrode, to ground, and.......... ?
Somewhere between the ground plane and the other side of the coil secondary is
a return path for the electrons.
Is it the capacitor? If it is, the capacitor is being charged by the secondary
current, not discharged.
Is it the battery? If so, the current would also have to flow through the
primary, and I think we would see that on the waveform, which we don't.
Distributed capacitance? Maybe, but I don't see that accounting for all of it.
I'm missing something here, and probably something obvious. When the light
finally goes on, I will most likely be embarrassed that I didn't see it
sooner. What am I missing?
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74
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