(Bemf) aka back emf or Counter emf (CEMF)

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Here is  a nice video.
Watch the green BEMF spark when the contacts get of each other.
Also watch the big coils!

Steve

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haha this is the spark which killed people during the Tesla days.

save yourself some bandwidth:
[youtube]http://www.youtube.com/watch?v=aSmMFog10D0[/youtube]

the green spark, didnt notice it at first, is it caused by the copper material?

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Hi Alan,

Thanks for finding the youtube version. I added the code for showing the link in yr post.
One of the reasons that i download such a video's, is because many good vids are lost, removed etc.
This way, we always have a nice copy on our forum!

br
Steve

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The green spark is the same color as i seen with my small relais setup.
Radiant_1 told me that it is typical for BEMF.
It always seems to have that color.

Shame so many uncarefull people died on that....

Steve

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The change of magnetic flux is practically infinite [d/dt], a huge drop in a small time interval creates a HUGE voltage to oppose this change, this ionizes the air, and current flows that creates the plasma. Now what would happen if the electrons are forced to stay stationary while let something [wfc?] see this 'infinite' emf?  
This happens in the VIC when the pulse goes low, but somehow inhibits the amps to flow.
I think we want a steep and stable 12V pulse go into the VIC so only an EMF pulse will be created in the chokes during rise and fall and SS will prevent ringing oscillations.

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@Steve
Green is only typical for BEMF if the contacts are copper. If it's Stainless it's a white color, same with lead. If it has more nickel/cobalt it's blue...etc....etc
So what does this mean??...Well, those are colors of the metal's oxides. What's happening is an atomic reaction. The huge potentials of the BEMF are ionizing/vaporizing the metals...so, be careful not to breathe this crap in. You will get heavy metal poisoning if you are careless...TRUST me I know 

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@Alan

haha this is the spark which killed people during the Tesla days.

No it's not....if you read Tesla's own accounts of the phenomena it is clear that is a much different thing indeed.
If you notice, this reaction happens AFTER the switch is closed in fact upon the re-opening.
Tesla describes something MUCH DIFFERENT...what he describes, happens on very large, very HV generators, and, it happens the second they close the circuit. He describes hair-like bluish corona, then gigantic arcs of lightning. These observations led to his experiments with disruptive discharge of HV capacitors and the further observation of stinging sensation while doing so...this led to his "Aether" theories.

I'm not trying to be a "know it all" but, I spent extensive hours reading, reading patents, reading Tesla's notes...etc....etc, and trust me this is not what Tesla was talking about.

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Google "Tesla Hairpin Circuit" on youtube.  It's only half of the demonstration.  Without the top shunt the spark is a normal hair thin spark.  With the shunt it's a totally different animal.  I saw a live presentation at the AEPC 2009 show and tell in Waldorf MD this past weekend.  I'm waiting for the video to show up on the net.  All the presentations were taped.  There are bits and pieces showing up here and there.

Regards,
Andy