Electronics > Learn more about electricity !!!

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

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

Steve

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

save yourself some bandwidth:

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

Steve:
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

Steve:
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.... 8)

Steve

Alan:
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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