Silly question about voltage and current

[TinselKoala]

Now, please FOCUS, this is very simple question : if electrons movement is the reason for electric current then why it require CLOSED CIRCUIT ? Take a charged electrolytic capacitor with HUGE energy stored (like those big ones used for power factor correction) , connect negative terminal to some place having less electrons like maybe other capacitor positive terminal), then measure how much electrons moved to that empty place by simple voltmeter. I think you would find nothing changed, capacitor still charged ,energy still there, electrons won't move easily...


Waiting for your comments

I think you would find that the _other_ terminal of the capacitor has the opposite charge, and opposites attract, across the cap's dielectric. There is no current pathway in your hypothetical question for the charges to equalize _across the capacitor's dielectric_. Why should the electrons, or rather the charge they carry, travel away from someplace that they are strongly attracted to by the presence of all that opposite charge on the other side of the dielectric? You've offered them an extremely high-resistance non-pathway in the other direction along a very strong electric field gradient .... an open circuit as you have set up. There is no pathway for the equal and opposite charges in the capacitor to neutralize.

[Farmhand]

Im sorry the sarcasm was rude, just take a little time study electron flow, the direction it moves through a diode, the bemf and the direction it moves through a diode.
You will realize the bemf has an opposite polarity, this imply's that a neg pulsed coil will have a pos return and a pos pulsed coil will have a neg return.
Study ionization, the plarity of the electrodes, the ion clouds formed around the electrodes, how that relates to a pos and neg pulsed coil.

Alternating current is more that it imply's, a coil pulsed with alternating current receives a pos and neg pulse.
Check out static neutralizers and you will see how your neutralizing any extra energy you may be drawing from the ambient by powering a transformer with both legs.
Split the pos and neg so they cant neutralize each other.

Dave take a good look at the scope shot and the circuit that produced it ( a few posts back), now notice that all the voltage is positive and all the current is positive,

If you look at the grounding point you will see that when the switch turns on the scope probe for voltage drops to zero, however the current rises positive and then declines positive. The  applied voltage is DC and on switch on the scope probe drops to zero volts then on switch off the voltage rises positive as the current declines positive.

There is no negative to it. Unless a wanted or unwanted oscillation causes it.

People say the voltage of the coil reverses but going by my scope shot I do not see how, the voltage is scoped across the coil and the voltage is always nil or positive.

If someone else would like to point out where the voltage across the coil reverses I would be glad to try to understand it.

Cheers

[Farmhand]

What happens is the coil changes from being a "load" to a "supply" and so the actual voltage "polarity" does not change nor does the direction of the current the only thing that changes is the end of the coil we think of as positive with relation to "load" "supply" situations, this is due to voltage level not positive negative as such. In other words when the coil is taking current the dot to designate the positive end of the coil is at the top, then when the coil is supplying current the dot to designate the coil polarity is moved to the bottom. It's a change in the mind only, to rationalize the thing we are seeing and so like minded people can communicate about it. There is much disinfo about DC pulsing of coils. And much is not explained by some of the other trained guys or too many people ignore them.

I don't mind to argue with them, because I feel anyone can be mistaken, I don't mind being wrong if I learn something, but most of the time they are correct, it's just that most of us do not understand how they say it. Or misunderstand what they say. And the misunderstanding goes both ways of course.

The discharge of a coil is forward emf (or just plain emf) as opposed to counter or back emf. This is seen by the current remaining to flow the same way, the voltage reversal across the coil happens when the coil discharge causes a higher voltage than the supply, but it does not go negative.

Cheers

[TinselKoala]

Farmhand, your coil circuit appears to be "overdamped" or even critically damped,  in that there is no trace of an oscillatory ringdown when the supply is cut off.  Other circuit parameters could be adjusted so that a ringdown at the resonant frequency of the circuit could appear, maybe. This may or may not have a good or bad effect on the performance depending on what the goal is.

[MarkE]

When an L/R or L/C circuit is switched must faster than the reactive network time constant, trapezoidal waveforms such as seen in farmhand's oscilloscope captures result.