Author Topic: MH's ideal coil and voltage question (Read 487914 times)

tinman · « **Reply #1305 on:** June 25, 2016, 07:39:43 AM »

Quote from: picowatt on June 25, 2016, 06:59:02 AM

MH,

I believe the "opposite" current that Tinman is discussing is with reference to the induced voltage that creates opposing currents as per the definition of CEMF. But again, I never read that to mean he believed the CEMF actually reversed the flow sufficiently to "charge the battery" so to speak.

As for the rest of what he is saying, well, that is why I suggested he consider looking into superconductors.

All conductors are inductors, and according to what he is saying, current could not flow through a length of superconducting wire (or at least no more than flows at T=0). So we kinda' know that can't be right.

There is nothing wrong with leading a horse to water, but...

PW

PW
I have never said that there would be a current flow going back into the battery.
Here is what i said
Quote post 1390-->What you dont get,is that the reverse current flow is subtracted from the induced current flow,and you cannot separate the two,as one subtracts from the other,and all you see is the end resulting value.

MH came up with this !reversed!(self induced current) current flow going back into the battery/power supply,when he tried once again to make me look like a fool,in post 1372-->
So like if the 5th time constant current is 100 amps and the 1st time constant current is 25 amps then the reverse current produced by the CEMF is 75 amps. So does that mean when you first apply the voltage across the coil the current is -75 amps? It's "Attack from Planet Bizarro and the Pumpkin Patch Creatures."

This was his response when i stated that-Quote:The value of the current flow produce by the CEMF is less than that induced by the applied voltage. It you take the peak current value that will be flowing at the 5th time constant,and you subtract from that the peak current value of the first time constant,you are left with the calculated reverse current produced by the CEMF. As you can see,the current produced by the CEMF ,is less than that of the induced current by the applied voltage.

So as you can see,MH plucked this !reverse current flow back into the battery! out from his own blunder on calculating what the current flow would be after 1 time constant,when the steady current flow value after the fifth time constant would have an end value of 100 amp's.

So now you see why these issues keep coming up,and a threads become 100's of pages long.

For me, there are only two outstanding issues and I will mention them again and I will put them in a better sequence this time:

1. MH gets up the learning curve , and clearly demonstrates that he understands what he is doing.
2. MH admits that he is wrong when he stated that my response to what CEMF is,how it creates a current that is in opposition to the induced current,and how it reacts against,or impedes upon the induced current,was incorrect.

Brad

tinman · « **Reply #1306 on:** June 25, 2016, 09:15:36 AM »

Quick setup showing the EMF and CEMF in a DC motor in real time,as a load is applied.

https://www.youtube.com/watch?v=SqPur5JUumg

Brad

tinman · « **Reply #1307 on:** June 25, 2016, 11:13:47 AM »

Quote from: Erfinder on June 25, 2016, 10:29:12 AM

Can't really tell from the video. What interests me, is when the consumption goes to zero, and then negative. I experience zeroing of the consumption often...as seen from the meter of my supply, when this happens, it means that my "self-induced voltage" is higher than the applied, but unlike in your demonstration, my machine does not continue to motor strong.

Regards

Quote

Where you are saying "induced", the text books say "applied". That being said, the comparison is applied versus self-induced EMF (CEMF), applied versus self-induced current.

Current is not applied to the motor,it is induced by the applied EMF.

Quote

This leads me to ask where the energy is coming from that keeps your rotor running strong even after the consumption has gone to zero, because technically it shouldn't be.

Technically you'd be correct

Quote

Regarding the inversion of the current, I would like to get into that, however, it would be best if you addressed my noted concerns, you aren't obligated to do so, I am just curious, and am probably one of the only ones who is really listening, to what you are saying and demonstrating "right now".

There are a few following this thread,so i dont think it will be missed lol.

Quote

During the video you state "as we increase the load on our motor...", you then adjust the pot. One speculates that the CEMF labeled motor, is functioning as a "generator", the load across it being the pot.

Yes,that is the load motor-(CEMF) motor,but as the self induced current increases past the value of the EMF induced current,then it becomes the motor,and the(EMF) motor becomes the generator,and so the current reverses through the CVR

Nothing special happening there

Brad

hoptoad · « **Reply #1308 on:** June 25, 2016, 12:29:50 PM »

Quote from: Erfinder on June 25, 2016, 12:01:20 PM

Current is applied to the motor, self-induction opposes, via an induced EMF, the build up of the applied current. In this wise, to say that it, the applied current, is "induced" by the applied EMF is inaccurate. Can you demonstrate current being "induced" by the applied EMF, using your present demonstration platform?
What is this thing you are calling "EMF induced current"?
Regards

While the term used may appear confusing, it is correct. You don't get current until a voltage source (EMF) is applied to a load circuit.
So the voltage (EMF) is applied to the load circuit, and this application of the voltage (EMF) to the load circuit induces a current to flow in the load circuit. So yes, the applied current is actually an EMF induced current.

Personally I would call the EMF induced current an applied current or source current, but it's really a semantic issue, which should be clarified by the context of the use of the term.

However, your confusion highlights yet again how everyone needs to be on the same page with terminology.

induce : meaning
ɪnˈdjuːs/verb
1.
succeed in persuading or leading (someone) to do something.
"the pickets induced many workers to stay away"
synonyms:persuade, convince, prevail upon, get, make, prompt, move, inspire, instigate,influence, exert influence on, press, urge, incite, encourage, impel, actuate, motivate;
2.
bring about or give rise to.
"none of these measures induced a change of policy"
synonyms:bring about, bring on, cause, be the cause of, produce, effect, create, give rise to,generate, originate, instigate, engender, occasion, set in motion, develop, lead to,result in, have as a consequence, have as a result, trigger off, spark off, whip up, stir up, kindle, arouse, rouse, foster, promote, encourage;

Cheers

MileHigh · « **Reply #1309 on:** June 25, 2016, 12:47:50 PM »

Brad:

How about just fixing this comment of yours:

<<< Yea--good one MH--only we do not have a loop,we have a coil attached to a voltage supply. >>>

Can you do that?

MileHIgh

hoptoad · « **Reply #1310 on:** June 25, 2016, 01:07:16 PM »

Quote from: MileHigh on June 25, 2016, 12:47:50 PM

Brad:

How about just fixing this comment of yours:

<<< Yea--good one MH--only we do not have a loop,we have a coil attached to a voltage supply. >>>

Can you do that?

MileHIgh

Yes, I do agree, that is a bit of a misnomer by Brad which he should acknowledge. Any load on a power supply of any sort (including a battery) that results in a current flow, be it a single wire or a coil across the terminals will create a full current loop within the supply and load.

Interestingly, a simple resistor connected directly across the battery will have the same voltage readings across it as the battery it is connected to and could be considered in parallel with the battery voltage, but the current from the battery through the resistor back into the battery is considered as taking a series path.

Cheers

picowatt · « **Reply #1311 on:** June 25, 2016, 05:24:23 PM »

Quote from: tinman on June 25, 2016, 09:15:36 AM

Quick setup showing the EMF and CEMF in a DC motor in real time,as a load is applied.

https://www.youtube.com/watch?v=SqPur5JUumg

Brad

Tinman,

I have always preferred using counter-EMF (CEMF) with regard to inductors and back-EMF (BEMF) with regard to the action of motors. If used interchangeably, one must be sure to indicate which action is being referred to within the context of its usage.

From the following Wiki:

https://en.wikipedia.org/wiki/Counter-electromotive_force

Quote

The term back electromotive force, or just back-EMF, is most commonly used to refer to the voltage that occurs in electric motors where there is relative motion between the armature of the motor and the magnetic field from the motor's field magnets, or windings. From Faraday's law, the voltage is proportional to the magnetic field, length of wire in the armature, and the speed of the motor. This effect is not due to the motor's inductance and is a completely separate effect.

PW

ramset · « **Reply #1312 on:** June 25, 2016, 06:57:59 PM »

Miles
absolutely lives for the "out of context" examples where the subject matter is self evident and profoundly obvious
but the ambiguity can be greatly enhanced and his EGO even more so if he can take twenty pages or more to show just how important he really is around here.

Miles has indeed formed a semantic EGO loop with several "Impotent feeds" to draw from...
this will truly Loop in perpetuity and most likely many more good Members will "CLICK"
their way out of this Forum [as Miles stamps errr Clicks another X for job well done .

Miles
Quote
"Can't wait to put an end to this once and for all"

oh, and Miles will be holding a spelling class next Tuesday
so we can do a better job on the OU Bench.....

MileHigh · « **Reply #1313 on:** June 25, 2016, 07:18:02 PM »

Like I already said Chet, I think it's really all about you stroking your own ego up and down and up and down to get some good resonant motion going.

ramset · « **Reply #1314 on:** June 25, 2016, 07:23:57 PM »

Miles
forgot to mention
I have to cancel on your Thursday night "folding your way to a better OU experimenter"
napkin folding class .

Yes ..
resonance was sooo misunderstood until you came along...
completely changed the way we do things around here...
Sooo helpful and informative !

I am signing up for your "Tying your way to a better OU Bench"
shoelace class for certain....

MileHigh · « **Reply #1315 on:** June 25, 2016, 07:36:37 PM »

Much to your chagrin Mr. Wannabee Ignorance Enforcer, indeed some people now understand what true resonance really is, and they understand what it is not. Resonance is NOT a timing delay device that results in better synchronous timing for a machine at one specific operational frequency. Stomp your feet or bang your head against the wall as much as you want, the truth will not change. I know that the spread of knowledge upsets you, so just go back to your hate and your polishing.

3Kelvin · « **Reply #1316 on:** June 25, 2016, 07:42:33 PM »

OFF-Topic+++OT++OT

Hello Together,
i try to understand the ideal coil , ideal source question.

My math skills are very rusty and due to i need a refresh to understand the scientific discussion in this thread.

My question:
What is the meaning of "dA" ?
So far, i be able to remember it is a change of the area like a2*b2 - a1*b1 = Delta A [Rectangle]

What relationship dA is mentioned due to a magnetic field?
What kind of relation is dA in the context of magnetic fields?

Sry for the double question,
my English is not so good.
Try to become better

Thx for your answers.

Love + Peace
3K

partzman · « **Reply #1317 on:** June 25, 2016, 07:55:43 PM »

I don't wish to add fuel to any fire here but I do have a logical question. I will refer to the quoted portion below from Wikipedia's Counter-Electromotive Force.

Quote: "The counter-electromotive force (abbreviated counter EMF, or CEMF),[1] also known as the back electromotive force, is the voltage, or electromotive force, that pushes against the current which induces it. CEMF is the voltage drop in an alternating current (AC) circuit caused by magnetic induction (see Faraday's law of induction, electromagnetic induction, Lenz's Law). For example, the voltage drop across an inductor is due to the induced magnetic field inside the coil.[1][2] The voltage's polarity is at every moment the reverse of the input voltage.[1][3]"

Now I ask this, in a simple circuit with a supply having an inductor connected across it, how can you have CEMF in the inductor that is in opposite polarity to the applied supply voltage as stated above when the supply goes from 0 to some amount at T0 and remains for a period of time? Where is this CEMF hiding? How do I measure it? Or does it really exist in this example?

Curious minds wish to know!

pm

poynt99 · « **Reply #1318 on:** June 25, 2016, 07:56:10 PM »

Going back to my simplified example...

Given:
L=5H
V=+4V

What happens:
At t<0, XL=0
At t=0, XL=infinity, and the current rises from 0A linearly at 0.8A/s.

At t=1, XL=5 Ohms
At t=2, XL=2.5 Ohms
At t=4, XL=1.25 Ohms
i.e. with every doubling of "t", "XL" goes to 1/2 of previous value. XL never reaches 0 Ohms.

At t>0 when I_L begins rising, an induced cemf of -4V is produced, based on Vcemf=L x di/dt. The cemf remains steady at -4V as long as di/dt stays at 0.8A/s. This of course occurs simultaneous with the application of 4V and the rise of I_L.

The question is, if emf=cemf, would it not makes sense that this result is created through an equalizing process? The amps/s rate ultimately being determined by the applied voltage and the inductance values.

The equalization I refer to comes about via the simultaneous process of an applied emf that wants to drive a current, vs. a reactionary process that wants to lower that current. To me this is very much like a negative feedback mechanism commonly used in linear amplifiers. Your amplifier may have an inherent gain of 1000, but through the application of negative feedback, the gain is reduced to some desired level, such as 100. In the case of our self-inductance, the negative feedback mechanism is the self-induced current and B field, which happens to oppose the B field resulting from the applied voltage. It is not quite an exact analogy, but conceptually similar. It all happens in real time, simultaneously, and only the end result is observable.

Perhaps it comes down to an applied emf, vs. an induced E field. We know the applied emf is 4V, but can we break the induced cemf (equivalent to the E field) down any further? Well, for a multi-turn inductor we can divide the cemf by the number of turns to obtain the induced cemf per turn. To me this would represent the actual value of the E field circulating around the inductor. So if we have a total cemf of 4V, and a 1000-turn coil, the actual induced E field would be 4/1000 = 4mV. This does not sound like much, but with R=0, 4mV could drive a significant current in a single loop, and each loop would carry the same current. I'm sure the induced current can be derived from the E field (or B field) and rate of change.

Some things to perhaps think about anyway. Sorry there are no definitive answers here. Still thinking about this.

ramset · « **Reply #1319 on:** June 25, 2016, 08:00:49 PM »

Miles
quote
"They know what resonance really is..."
---------------------------------------------------

Oh goody we can put that in with Electricity , magnetism and gravity then....

I profoundly disagree Miles
the day we truly "Know what resonance is "and how to make it work in all materials for our benefit.

will be a very big day.

as Smokey 2 was teaching you earlier in this thread.
oh yeah
he's another one of your CLICKS

well done... well done Miles ..
I can feel the breeze of you patting yourself on the back from here...

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Author Topic: MH's ideal coil and voltage question (Read 487914 times)

tinman

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