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### Author Topic: Silly question about voltage and current  (Read 43211 times)

#### MarkE

• Hero Member
• Posts: 6830
##### Re: Silly question about voltage and current
« Reply #45 on: February 28, 2014, 03:15:39 AM »
Ok sounds plausible for water, tell me if alternating current is just current alternating through a conductor then why does this circuit build a negative ion cloud on one end and a positive ion cloud on the other.
If negative current were the only energy moving in the coil wouldnt we have a negative ion cloud only on one end of the circuit.
Capacitance

#### Dave45

• Guest
##### Re: Silly question about voltage and current
« Reply #46 on: February 28, 2014, 04:06:19 AM »
Capacitance
comon Mark you can do better than that.

#### Farmhand

• Hero Member
• Posts: 1583
##### Re: Silly question about voltage and current
« Reply #47 on: February 28, 2014, 04:07:18 AM »
Ok sounds plausible for water, tell me if alternating current is just current alternating through a conductor then why does this circuit build a negative ion cloud on one end and a positive ion cloud on the other.
If negative current were the only energy moving in the coil wouldnt we have a negative ion cloud only on one end of the circuit.

Mark Is right, Dave we kinda need to think in a way that isn't so (positive-negative), not so (either-or) kind of thing. If one plate becomes more negative then the other plate becomes less negative in relation to it, or the same thing if one plate becomes more positive then the other plate becomes less positive and a potential difference occurs between them. Simple, the potential difference is between the two plates and they both share the charge differential.

Cheers

P.S. Dave maybe Mark is thinking, Come on Dave you can do better than that. I think you are getting ahead of yourself a bit, you're talking ion clouds, but you don't understand charge displacement. Maybe reading to too much Utikin, he is there to fill peoples heads with fallacies and make claims for Tesla he didn't make. Better to not read him, better to get a good basic understanding of electricity ect. However we all make our own choices. In that way we are free.

..

#### TinselKoala

• Hero Member
• Posts: 13968
##### Re: Silly question about voltage and current
« Reply #48 on: February 28, 2014, 04:24:40 AM »
And that happens because the circuit pumps electrons into the capacity at the negative end. This could be a large shape or just a point, with the other "plate" being the Earth itself or the other end of the circuit if, again, a shape or point is provided. Voltage is charge pressure, which comes from packing like charges together into some _capacity_. If you have sharp points or edges, the _gradient_ of the electric field becomes large enough to break down the air molecules into ions - at the "negative" end, electrons are emitted, latch onto air molecules and give them a negative charge. Opposite on the other end, the depletion or holes "suck" electrons out of the air molecules leaving them positively charged. The diodes in the circuit prevent a discharge path that way. Just as with any capacitor, as you pack more charge into the region, it becomes harder and harder to put more charge in because the charge already there repels the charge you are trying to stuff in.

Really, if you want to understand current and voltage you need to think about the movement of and forces between like unit charges. Electrons and holes. Water doesn't exactly repel itself and there's no "water holes" like there are unit positively charged "holes" in conductors and semiconductors, so the hydraulic analogy breaks down if you try to take it too far.

Voltage is "relative charge pressure", which Farmhand is describing, aka potential difference. If you stick both your voltmeter leads to the same charged surface you won't measure any voltage, even though the charge pressure might be very high compared to the "ground" ... the Earth is essentially an infinite sink and source for electrons and so it is the usual "zero reference" to which higher voltages... charge pressures... are compared.
But charge itself isn't relative, it is conserved. You can pack a bunch of charge onto a capacitance, and it won't discharge if there is no path to a lower potential (charge pressure). But it still takes more and more work to pack more charge into the capacitance to raise its voltage. Eventually you get so much charge into or onto a capacitance that the very air breaks down into ions which are very conductive, and the charge leaks away. The voltage rating of capacitors is essentially the dielectric strength that can withstand the potential difference between the plates.

#### Dave45

• Guest
##### Re: Silly question about voltage and current
« Reply #49 on: February 28, 2014, 12:35:59 PM »
Lets keep it simple
If current moves from neg to pos then current is moving through a diode in this direction

#### Dave45

• Guest
##### Re: Silly question about voltage and current
« Reply #50 on: February 28, 2014, 12:44:03 PM »
But the bemf from a pulsed coil moves through a diode in the reverse direction.
We can see this using a freewheel diode across a coil, or using this simple experiment.
So tell me what polarity is the energy moving through the diode from pos to neg.
Now I see the diode reroutes the energy from the bemf to the pos in a freewheel diode but the energy is moving through the diode in the wrong direction to be a neg polarity.

#### MileHigh

• Hero Member
• Posts: 7600
##### Re: Silly question about voltage and current
« Reply #51 on: February 28, 2014, 01:55:58 PM »
Dave:

I will take a stab at this one.  For starters, yes, "we" got it backwards and current flow is normally flowing electrons.   However, that is analogous to driving on the right in North America and driving on the left in the UK.  Does it really matter in the final analysis?  The resounding answer is NO, it does not matter.  Literally any problem solved with the standard electric current convention we use will WORK FINE, so there is no need whatsoever to keep harping on the fact that "(electron) current runs backwards through diodes" and all that stuff.  We simply accept the convention for what it is and stick to it in order to avoid mass confusion.  EVERY SINGLE PROBLEM WILL WORK using the standard electric current convention.  After you solve the problem, then if you really want to you can then say that in reality the electron current is opposite to the conventional current.  This whole thing is a useless tempest in a teapot.

For your diagram, I will assume that the left side of the voltmeter is the negative sense input, and the right side of the voltmeter is the positive sense input.  Believe it or not, it is a huge mistake for you to not put the polarity designations on your voltmeter inputs.

The diode in your diagram is not rerouting energy.  That is not proper terminology.  The diode either conducts or it doesn't conduct, and there is a measurable voltage across the two terminals of the diode.  When the diode conducts we will assume there is a voltage drop of 0.6 volts.   That means relative to your diagram the right side of the diode will be at <some voltage relative to the battery ground> and the left side of the diode will be at <some voltage relative to battery ground> minus 0.6 volts.   Note that when the switch is closed the left side of the diode will be at the battery ground potential.

From your diagram, let's assume the switch is closed and some current is flowing.  When the switch opens, the voltmeter will measure a large increase in potential while the current continues to flow through the air which has been broken down and is ionized and becomes a plasma.  When the coil has discharged all of its energy the current flow stops and the voltmeter will measure the battery voltage.  (there is a slight complication relative to the diode that I am ignoring here for the sake of simplicity)

That's it, the problem is solved.  If you really want to split hairs you can do the whole electron current business but there is no point whatsoever in going there.

MileHigh

#### TinselKoala

• Hero Member
• Posts: 13968
##### Re: Silly question about voltage and current
« Reply #52 on: February 28, 2014, 05:38:43 PM »
Lets keep it simple
If current moves from neg to pos then current is moving through a diode in this direction

Let's keep it even more simple and recall that "conventional current" is _defined_ as moving from Positive to Negative in circuits. Again, this is a _naming convention_  that we are stuck with due to the time delay between Benjamin Franklin's work with electricity, and the actual discovery and characterization of the electron, the actual carrier of the charge that does move in the circuit. All electrical engineering analyses like Kirchoff's circuit rules, Ohm's Law, the designation of Cathode and Anode in circuit components, etc. use the CONVENTION, even though we know that the actual electron charges are moving in the other direction. The CRT, for example, illustrates this quite well. Even though the Cathode is strongly _negatively charged_ , it _emits electrons_ in a beam,  rather than sucking them up like some kind of vacuum.

http://www.mi.mun.ca/users/cchaulk/eltk1100/ivse/ivse.htm
http://en.wikipedia.org/wiki/Electric_current
http://web.engr.oregonstate.edu/~traylor/ece112/lectures/elect_flow_vs_conv_I.pdf
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.html#c3

I don't make this stuff up!

#### Dave45

• Guest
##### Re: Silly question about voltage and current
« Reply #53 on: February 28, 2014, 11:04:09 PM »
I know how current flows in a diode normally, what I am try to get across is that the bemf from a negatively pulsed coil has a pos polarity, and we know this by the direction it moves through the diode.
You say Im splitting hairs well when looking for free energy your darn right, Im looking in every nook and cranny.

#### MarkE

• Hero Member
• Posts: 6830
##### Re: Silly question about voltage and current
« Reply #54 on: February 28, 2014, 11:15:35 PM »
I know how current flows in a diode normally, what I am try to get across is that the bemf from a negatively pulsed coil has a pos polarity, and we know this by the direction it moves through the diode.
You say Im splitting hairs well when looking for free energy your darn right, Im looking in every nook and cranny.
Your IRF510 MOSFET is upside down.  Connected like that with the source to the coil and the drain to the low side of the circuit current flows continuously through the MOSFET body diode.

What we know is that in the presence of a changing impedance inductor voltage changes  so as to maintain the current direction and magnitude.  Current was flowing clockwise through the coil.  Increasing the impedance through the switch causes inductor voltage to rise such that the current continues.  The diode eventually offers such a continuation path.  Before it does, energy gets stored in the local parasitic capacitance, and energy gets dissipated in the MOSFET as it transitions from a low impedance to a high impedance, and in the diode as it transitions from a high impedance to a low impedance.

#### Dave45

• Guest
##### Re: Silly question about voltage and current
« Reply #55 on: February 28, 2014, 11:20:58 PM »
Lets add a diode for clarity,
If the bemf from the coil had a neg polarity the freewheel diode would be reversed, but it isnt this indicates the polarity of the bemf is of a pos polarity.

#### Dave45

• Guest
##### Re: Silly question about voltage and current
« Reply #56 on: February 28, 2014, 11:23:27 PM »
Your IRF510 MOSFET is upside down.  Connected like that with the source to the coil and the drain to the low side of the circuit current flows continuously through the MOSFET body diode.
irrelevant to the discussion, this came from some circuit schematic I had on hand

#### MarkE

• Hero Member
• Posts: 6830
##### Re: Silly question about voltage and current
« Reply #57 on: February 28, 2014, 11:24:46 PM »
Lets add a diode for clarity,
If the bemf from the coil had a neg polarity the freewheel diode would be reversed, but it isnt this indicates the polarity of the bemf is of a pos polarity.
That configuration is actually used in a number of half-bridge power circuits to prevent conduction through the MOSFET body diode.

#### Dave45

• Guest
##### Re: Silly question about voltage and current
« Reply #58 on: February 28, 2014, 11:55:11 PM »
Why is this important, because we can use the pos energy to pulse a coil, now the diode works bidirectional it passes the pos bemf from the negatively pulsed coil into another coil, pulsing this coil with pos energy its bemf will be neg and will pass through the same diode, now your coils can ring back and forth.

#### MarkE

• Hero Member
• Posts: 6830
##### Re: Silly question about voltage and current
« Reply #59 on: February 28, 2014, 11:57:02 PM »
irrelevant to the discussion, this came from some circuit schematic I had on hand
Dave, if you don't draw things correctly then it is going to throw the conversation off.