Oh i see lol.

I say the very same thing as Poynt did,but i get a totally different reply.

To gutless to treat Poynt like you treat me?
Oh,and here is the kicker--the guy(me) that you think is such an amateur,and knows so little,gave the very same answer as Poynt,who is very well versed in EE--only i gave it first.

This speaks volumes about your true nature MH--your pathetic.

Brad

First of all, I don't know which posting you are referring to.  Secondly, kiss my ass.

Kiss my ass because Poynt made a long posting where he started to move significantly in my direction and your response was quite polite.  If I had said the same thing you would have said I lost my marbles and used a lot of other colourful expressions.  You were too gutless to treat Poynt like you have treated me?

In other words, your behaviour would be exactly the same as what you are accusing me of.  Here is where you can actually apply the term "hypocrite" to your own behaviour.

You are a hypocrite Brad.

i.e.;

And to think,you thought you had the smarts to give EMJ a hard time on his understandings about inductors and coils--and me for that matter.   <-- This one sounds like a rude insult.
You have yourself a great time MH,but i am done with your repeated stupidity,and re-writing of physics.  <-- this one sounds like a rude insult
I think you are a little lost when it comes to understanding what CEMF is in an inductor-or anything for that matter.   <-- This one sounds like a rude insult
Yep-you have finally lost your marbles.  <-- This one sounds like a rude insult
MH is just lost again.  <-- This one sounds like a rude insult

However, Brad, you might or might not know how after the fall of the Soviet Union in America they talked about the "peace dividend."

Well, let's say you got the "war dividend."  You can be so unbelievably obstinate and your knowledge was so screwed up and so skewed that you were hopelessly trapped in a backwards electronics pre-kindergarten.  You had to be battled with over and over and over to force some sense into you.  You still have a long long way to go.

You had to get your ass kicked over and over.  You were kicking and screaming all the way.  You still have a serious mental block about admitting that you are wrong.

Nonetheless, you have progressed more in the past three months than you progressed in the past six years watching pulse motors turn.

Don't believe me?  Just go read this thread from the very beginning and read yourself and what you have to say.  So for you, being told straight to your face by me that what you just posted was idiotic and completely and totally wrong who knows how many times was ultimately for your benefit.

Just go read the this thread from the very beginning and see how completely idiotic most of what you say is from your current perspective.

It's like very Old School schooling where knowledge had to practically be beaten into your behind.  And there is no way in hell I would keep this up.

Like it or not, you are 10 times smarter when it comes to electronics than you were three months ago.  And you still need to lock yourself in a room for a month and read and understand some books on basic electronics so you will stop dropping outrageously ignorant and stupid comments that make it look like you were born just yesterday.

I really do love that saying of verpies-->just because everyone else makes mistakes,it dose not mean we have to.

Brad

Exactly, so when is this mass hysteria about Kirchhoff's voltage law going to come to an end?

   Old Webby's gettin' a bit of steam up!!!
          J.

The EMF and the CEMF are the same damn thing!  The battery says, "I am imposing 12 volts across you."  The coil says, "Oh shit, then I have to let changing current flow through me at a rate where I muster up the same 12 volts."   They are the SAME THING.  They both measure 12 volts with a volt meter and have the same polarity if you use the same ground reference.  They HAVE to be the same potential because they are CONNECTED to each other.

They measure the same, but not because the cemf is equaling the emf. It is because the emf source is holding the voltage constant. again, I think it is a very bad idea to equate a voltage drop with a cemf. They just simply are not the same, and historically have never been used interchangeably.

If they are the same damn thing then why is one called CEMF?  It's because you "travel though the loop" in ONE DIRECTION only.  So if you go clockwise and you go UP in potential because of the EMF, then as you continue on your journey through the coil you go DOWN in potential.  Hence the "counter."  You go up in potential and then you counter that by going down in potential.  But when you are not "in the loop" the EMF and the CEMF are EXACTLY THE SAME with the SAME polarity.

I disagree. One is called cemf because that is precisely what it is; i.e. it is a generated voltage in this case. Going around the loop is simply confirming KVL, and it always holds.

The EMF and the CEMF are the same damn thing!

I am going to have to disagree with this.

I believe I understand what it is you are saying with regard to your definition of CEMF.  However, by your definition, even if your "black box" were empty (a perfect insulator), that perfect insulator would also be creating a CEMF equal to the "applied" EMF.  And, by your definition, I can even see the argument that can be made to make the case for that being true.
   
However, this thread is about inductors and the definition of CEMF, regarding inductors, is very well defined.  As defined, the CEMF related to inductors is generated by way of a very specific mechanism (induction).  With all the harping on about the use of proper terminology, and to avoid confusion, it is perhaps best to stay with the existing definition of CEMF as it relates to inductors.

In the above you state that EMF and CEMF are the same thing.  You make this case based solely on a voltage drop measured across the two terminals of the inductor.  When connected across an ideal voltage source, the voltage measured across the inductor has little to do with the defined mechanism and actions of an inductor's CEMF.  In fact, by using only a voltmeter to measure across the inductor, it is impossible to measure, or identify, any parameter related to the inductor's CEMF.  By definition, the CEMF will oppose _current_ and in order to see the effects of CEMF (as defined), one must measure current.

The voltage portion of the definition related to an inductor's CEMF is, rather clumsily, something along the lines of "a rate of change dependent voltage induced into a conductor that produces a _current_ in opposition to the current that induced it".  Whether or not the induced voltage related to an inductor's CEMF is realized externally across the inductor's two terminals will depend heavily on the impedances external to the inductor.  In the case of being connected across an ideal voltage source, the effects of an inductor's CEMF will not manifest externally as a voltage.  Only by measuring the rate of change dependent opposition to the flow of current can the effects of an inductor's CEMF be realized.

Tinman's question, "what if the EMF and CEMF were equal", with regard to an inductor connected to an ideal voltage source, had little to do with any _voltage_ measured at the two terminals of the inductor.  In this instance, CEMF will only manifest by measuring current.

As I responded to Tinman, if it were somehow possible to cause all the magnetic flux created by a current flowing thru an ideal conductor to be confined to, and cut thru, that conductor in such a way as to make the inductor's CEMF be equal to the EMF, I believe that inductor would have infinite inductance.  To avoid the "chicken or egg paradox" in answering whether current could flow thru such an inductor, I stated that I believed that an infinitely small current would flow over an infinitely long period of time.

At no time were we discussing CEMF in reference to any _voltage_ measured across the inductor.   

Just my .02...

PW       

What have I learned today?
 EMF is not a force.
      J.

May the EMF be with you...

PW:

Your posting is a doozie and I am always amazed how sometimes it feels like you a permanently prepped to write a final exam because you have all of the hard-core theoretical and technical information at your fingertips, which is something that I don't have.

You responded to my statement, "The EMF and the CEMF are the same damn thing!"  Just a quick recap from what I just posted:  I am talking about the measurement of the voltage magnitude itself.  i.e.; Are the EMF and the CEMF the same value or is there a "requirement" for there to be a difference between the two values for current to flow?

You bring the focus of the CEMF discussion back to inductors which is fine.  I have conceded that point and said for resistors "potential difference" is more appropriate and less confusing.

When connected across an ideal voltage source, the voltage measured across the inductor has little to do with the defined mechanism and actions of an inductor's CEMF.  In fact, by using only a voltmeter to measure across the inductor, it is impossible to measure, or identify, any parameter related to the inductor's CEMF.  By definition, the CEMF will oppose _current_ and in order to see the effects of CEMF (as defined), one must measure current.

I agree and I cited Wikipedia and that is mentioned in the first sentence of the article, "The counter-electromotive force (abbreviated counter EMF, or CEMF), also known as the back electromotive force, is the voltage, or electromotive force, that pushes against the current which induces it."

What I am not saying and what is implicit is that if you measure CEMF on an inductor with your voltmeter, you are aware that increasing current is flowing through the inductor and that is the real mechanism at play.  You don't even know the magnitude of the increasing current, you are only aware that the process is taking place.

I don't know if you _must_ measure the current.  If you know the inductance, and you measure the voltage you at least know the rate of change of the current, but you don't necessarily know the magnitude of the current, unless you know the initial conditions, etc.

Whether or not the induced voltage related to an inductor's CEMF is realized externally across the inductor's two terminals will depend heavily on the impedances external to the inductor.  In the case of being connected across an ideal voltage source, the effects of an inductor's CEMF will not manifest externally as a voltage.  Only by measuring the rate of change dependent opposition to the flow of current can the effects of an inductor's CEMF be realized.

I am puzzled by that statement with respect to an ideal voltage source.  Are you making reference to a real-world inductor with resistance?  I didn't state it explicitly before but I am assuming an ideal inductor unless stated otherwise.  If you do mean a real-word inductor then I agree, the CEMF could be mixed in with an IR voltage drop.

Tinman's question, "what if the EMF and CEMF were equal", with regard to an inductor connected to an ideal voltage source, had little to do with any _voltage_ measured at the two terminals of the inductor.  In this instance, CEMF will only manifest by measuring current.

Are we back to a real-word inductor as I referenced above?

As I responded to Tinman, if it were somehow possible to cause all the magnetic flux created by a current flowing thru an ideal conductor to be confined to, and cut thru, that conductor in such a way as to make the inductor's CEMF be equal to the EMF, I believe that inductor would have infinite inductance.  To avoid the "chicken or egg paradox" in answering whether current could flow thru such an inductor, I stated that I believed that an infinitely small current would flow over an infinitely long period of time.

I can't see where you are coming from for this one.  In my mind the inductance value from a coil of an ideal conductor is still a function of geometry as per the derivation.  So you can go to the Hyperphysics web site and punch in the coil parameters and then get your inductance value and take it from there.  I can't envision an infinite inductance here.

When you say, "all the magnetic flux created by a current flowing thru an ideal conductor to be confined to, and cut thru, that conductor" to me that means a "perfect coil" where the magnetic flux still flows through the center of a coil, and then wraps back around the outside of the coil through all 3D space.  I just don't see an infinite inductance with that model.  I suppose if you had an infinite number of turns in the coil form that would be a different story.

MileHigh