Silly question about voltage and current

[Dave45]

Yes please. If we use the term "current" can we agree to stick to the established convention of the direction of "travel"? And if we are talking about charges, then let's call them charges and accept that they go the other way around the circuit. But if we are analyzing circuit behaviour from the standpoint of electromagnetism, power dissipation, and all that, we should stick with the established convention, even though we know it is "wrong".  Drive on the left side of the road if you are in Britain or Japan, please, and if you are on Earth.... current (consider "conventional" as always implied) goes from positive  to negative.

[MarkE]

Dave, which convention is used does not end up mattering mathematically.  Negative current convention dictates that current flows from the negative pole of a power source back to the positive pole.   Positive current convention follows the opposite path.  Negative going CCW or positive going CW yields the same results.

[TinselKoala]

Very funny Dave. If I were to use a cartoon to describe your viewpoint, the head would be stuck up a different hole.

[SeaMonkey]

Circuit Diagram posted by Dave45 here:

(http://www.overunity.com/14343/silly-question-about-voltage-and-current/dlattach/attach/134173/image//)

Open the above link in  a New Tab in order to see the
image.

There really isn't anything wrong with the depiction
of an N-Channel MOSFET functioning as a Low Side
Switch.  The arrow depicting the direction of switched
inductor current flow, when considering the polarities
of the semiconductor components, must refer to
"electron flow."  The associated power supply polarity
is therefore self evident.

The red-letter label starboard of the Spike Suppression
Diode which parallels the inductor is incorrect, however.

The Inductor Discharge Kickback will forward bias the
suppressor diode with a resultant current flow consistent
with the Time Constant of that portion of the circuit.

The direction of current flow through the inductor in
both cases (charging and discharging) will be the same.

[Farmhand]

OK so I was mistaken in my first test and admit it, I'll explain where I went wrong later.

Anyway With the circuit posted below, I see that there is indeed a current through the coil snubbed by the diode to the supply, and it seems to cause a continuous current in the coil I used, which heated it right up.  However when the coil was discharged to a higher voltage the current went to zero. Which is desirable to me.

I don't like coil snubbing, I was never sure why, then I thought I knew why, but now I know I know why I don't like it. 

First picture is the circuit the dashed portion is the alternative/second arrangement.

Second shot is with the diode snubbing the coil to the supply.

Third shot is coil discharging through a higher voltage.

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P.S. I better recheck things. 

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Seems correct Yellow trace is inverted on the scope to make it correct I think.

With the diode snubbed to the supply rail it uses 500 mA (maybe more) and heats up the coil but with the coil discharged to the battery it uses only 200 mA (maybe 300 mA) and doesn't heat up the coil and the current goes to zero.

I did the original test to try to show why I think snubbing is bad and this test shows even more reason fo me so I am very glad I did it.



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