Perhaps you could tell us all,as to why the current dose not shoot straight up to it's steady state value,when a voltage is place across it
What impedes on that current flow?

Brad

*CLICK*

You should not even be asking that question at this point in time.

 author=MileHigh link=topic=16589.msg487098#msg487098 date=1466818180]

That's a real doozie Brad.  Let's see, I probably first learned about a time constant in 1977.  Do you really think I don't know what the approximate values are?  I was tired and just threw up some arbitrary numbers for illustrative purposes.

What a whole lot of crap MH.
You threw those numbers up to make my explanation look wrong,but it is right,and you are a lyre.

So here you are making a complete fool of yourself, a spectacle of yourself, by "pretending" that I don't know the approximate value of the first time constant.  That's you cynically being an asshole for all to see.

What it shows MH,is how deceitful you can be,in trying to make some one else look wrong.
But once again,i caught you out in your pathetic attempt at doing so.

You are such a little imp, I think you need a good spanking.
Bad little imp boy!  You read multiple times how I agreed that it is more appropriate to avoid that term for a resistor.  Little imp boy needs another spanking, count down from 200.
Now count down from 300.
Now count down from 400.  That's what you call beet red for being a bad boy.

Your pathetic.
You are also no where big enough to give me any sort of spanking--you never have,and never will.

No it doesn't create a current flow in the OPPOSITE direction.  That is a nonsensical idiotic fantasy that does not happen and you will never find a single stitch of evidence for that.  It's a bad-old-days belligerent Brad fantasy.

Wrong again,as i can show it on my bench--no problem at all.
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.

The EMF source is say a battery, and the CEMF source from the coil looks like another battery.  That's two EMF sources facing each other at the same potential and so NO CURRENT FLOWS towards the battery driving the coil.

And there you go--you just shot your self in the foot again.
You said that the CEMF is always equal and opposite to the EMF,but current will still flow.
Now you have just shown us all that if the CEMF and EMF are the same value,no current will flow lol ;--Good one MH 

 

You have about as much electronics common sense as lumpy gravy.  Your whackadoo fantasy story is completely and utterly ridiculous and after all the work that was done in this thread you should be embarrassed for regressing once again.  Like I have told you, GET SOME ELECTRONICS BOOKS AND LOCK YOURSELF IN A ROOM FOR A MONTH AND READ THEM AND UNDERSTAND THEM.

My lumpy gravy MH,is the same lumpy gravy that PW,Poynt,Hoptoad,and everyone else here are eating.
Sorry cobba--you have been outvoted on this one.

Anybody can read this thread from the beginning through the end with a doorman's clicker, the type used to count the number of people in the club.  Every time you have "a moment" the person can register a click.  Seriously, you wouldn't want to know what the count was when they got to this very posting.

I think you had better take a walk back in time MH,and see who has the most clicks against there name-->you win hands down.
We have had all sorts of wackadoo from you in this thread,and the JT thread--the latest being your attempt to discredit what i said about the CEMF current value being the difference between that of the peak current at each time constant,and the steady state current.
I was correct,and you were of in wackadoo land.

Here is what i said--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.

Here is your attempt to discredit my claim
Quote: 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."

As you can see,an idiotic attempt to discredit what i said,and the only bizarro comes from you.
You know dam well that if you had of used the correct values for each time constant,what i stated is absolutely true. But no,you had to pluck some incorrect numbers out of your wackadoo head,so as to try and make others believe that i dont know what im talking about--your pathetic.
The correct amounts using your 100 amp steady state current flow.
At the end of the first time constant,the current flowing through the coil will be 63.2 amp's,and the reverse current value from the self induced EMF will be 36.8 amps.
Perhaps PW,Poynt or Hoptoad would like to confirm what i said.

MH-face it--you got caught out again at trying to discredit me,and you had another epic fail-as you do often-->the latest being your CEMF producing resistor.
I was the first to tell you that is crap,and you gave me a mouthful,and said i had no idea what i was talking about. But then Poynt,PW,and Hoptoad had to slap some sense into you,and now you have admitted it was another stupid thing to say.


Keep going MH,your hole is getting deeper by the day.


Brad

This is one of those times when it feels like it is completely and utterly hopeless with you Brad.

And there you go--you just shot your self in the foot again.
You said that the CEMF is always equal and opposite to the EMF,but current will still flow.
Now you have just shown us all that if the CEMF and EMF are the same value,no current will flow lol ;--Good one MH 

*CLICK*

No current will flow into the battery due to the CEMF from the coil.

Current will flow due to the battery's EMF being imposed on the coil due to the nature of the coil.

But you are such an electronics simpleton sometimes that some basic critical thinking skills like looking at the situation from both perspectives is beyond your thinking capability.  It's just hopeless.

MH,

Tinman defined CEMF as follows:

When a voltage is placed across a coil, the current will change quickly from zero. This  change creates an expanding magnetic field around the coil, and when this happens,it induces a voltage back into the coil. This self induced voltage is known  as back EMF,or CEMF,and creates a current flow in the OPPOSITE direction to the current flow that induced it in the first place.

Were I grading papers, I would merely have scratched out the words I highlighted in bold above, and replaced "the OPPOSITE direction" with the word "opposition" so that it reads "creates a current flow in _opposition_ to the current flow", just to clarify and be a bit more precise.

If I wanted to nitpick at it a bit further, I might also have circled "CEMF" and wrote "preferred" next to it, and possibly replaced the word "coil" where used with the word "conductor" (unless the question specifically asked about a coil, and not just a generic inductor).

I would also have been tempted to insert "flowing through it" in the first sentence so that it reads "the current _flowing through it_ will change from zero".

However, I would have given full credit for his response, as it demonstrates a basic grasp of the concept.

I know the two of you have been at odds for some time, but the rather demeaning nature of your response seems a bit much. 

PW

MH,

Tinman defined CEMF as follows:
Were I grading papers, I would merely have scratched out the words I highlighted in bold above, and replaced "the OPPOSITE direction" with the word "opposition" so that it reads "creates a current flow in _opposition_ to the current flow", just to clarify and be a bit more precise.

If I wanted to nitpick at it a bit further, I might also have circled "CEMF" and wrote "preferred" next to it, and possibly replaced the word "coil" where used with the word "conductor" (unless the question specifically asked about a coil, and not just a generic inductor).

I would also have been tempted to insert "flowing through it" in the first sentence so that it reads "the current _flowing through it_ will change from zero".

However, I would have given full credit for his response, as it demonstrates a basic grasp of the concept.

I know the two of you have been at odds for some time, but the rather demeaning nature of your response seems a bit much. 

PW

Thank you PW.

I am willing to lean,but i am not willing to let MH make me look like i have no idea as to what is going on here.
I would like to have good standing with those around me,but MH is doing his best to discredit that good standing,and i just cant sit back from that,and i dont believe you,Poynt,or anyone else would either.


Brad.

Thank you PW.

I am willing to lean,but i am not willing to let MH make me look like i have no idea as to what is going on here.
I would like to have good standing with those around me,but MH is doing his best to discredit that good standing,and i just cant sit back from that,and i dont believe you,Poynt,or anyone else would either.

Brad.

Fix this statement Brad to show you have an idea:

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

PW:

Pushing 100 thread pages to get Brad and others to understand how an inductor works and you get this from Brad:

----------------------------------------------------------------

[Part 1 from Brad]

If R=0, then the current will climb at a steady rate fo all time-right?--no-wrong.
If the flow of current from T=0 is going to rise at a steady state,then the apposing current generated from the CEMF will also rise at a steady state. So what dose that mean for the current induced by the applied voltage?

[Part 2 from Brad]

No,this has not been covered already.

The CEMF is created by the changing magnetic field,which is due to the increasing current over time,that was induced when the voltage was placed across the inductor
This CEMF creates a current flow that is in the opposite direction to that of which the applied voltage induced. 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. This means the remaining difference is flowing through the coil at the end of the first time constant. The greatest amount of CEMF is produced at T=0,and so the greatest amount of reverse current is produced. This is why the inductor draws the least amount of current at T=0-because the difference between the revers current from the CEMF,and the induced current from the applied EMF ,is at a minimum.

The CEMFs value,and so the value of reverse current,is dependant on how much the magnetic field is changing over time. As the magnetics field change over time slows,less reverse current is produced,as the CEMF value is less. This is why the current induced by the voltage starts to rise over time.

If the current is going to continue to rise-such as it would in your question,then the magnetic field would continue to increase at a steady rate. If the magnetic fields change in time is a constant (as it would be for your ideal coil),then the CEMF would also be at a steady value-as Poynt has answered.

The magnetic fields rate of change over time  in a coil with no resistance,remains at a constant value,and that value is what it was at T=0--the instant the ideal voltage was placed across the ideal coil.
The current value will never increase from what it was as T=0,as the magnetic fields change over time remains at a constant value,and so the self induced EMF also remains at a constant value-->and there for,the reverse current also remains at a constant value.

So,regardless of what you believe, the answer to you question is--the current will not increase any higher than it was at T=0--regardless of the time the voltage is applied to the coil for.

Brad

-----------------------------------------------------------

After nearly 100 thread pages and finally answering the famous question as well as all of us responding to hundreds of secondary questions and assuming that Brad finally had a decent grasp of the material, we get the comments above.  I can barely comprehend some parts of the prose because it sounds to me like near-gibberish.  However, it appears to be pretty clear that he believes that there is a "tangible reverse current" due to the CEMF somewhere in the mix when you connect a battery or EMF source to a coil.

Hence my frustration, and myself and Brad had a little mutual trash talk.  I am very tempted to just walk away.

MileHigh

author=MileHigh link=topic=16589.msg487109#msg487109 date=1466824385]


 

Yes, a coil will produce a CEMF when you connect a battery up to it.  And the true definition of CEMF is based on the rate of the changing current flowing through the coil.

That is correct,and the CEMF is never the same value as the EFM,as you have stated on more than one occasion now that the EMF and CEMF are the same value ,you are wrong when you state that about inductors and motors.'

The bottom line is that it is the battery that causes current to flow into the coil, and any talk about the CEMF causing current to flow into the battery, tangible or hypothetical, is wrong.  We are talking about a simple single current loop here.

No, one here has ever stated that current will flow back into a battery--this is a misleading comment by you,and you should retract it.
If you had bothered to take the time to read what i said,you would have seen that the reverse current value(the self induced current) is subtracted from the current induced by the voltage that is placed across the coil.

Brad can talk trash too, so don't always paint me as the "bad guy."  Reading his crazy theory was extremely disappointing to me.  It is what it is.

If your talking about what we are discussing here,now,about the self induced current,then it is not trash talk--it's just beyond your means of understanding.

There is nothing wrong with making a very strong point sometimes, especially when it would appear almost nothing registered going the polite route for all these years.  You won't even tell him in simple terms that he is wrong sometimes, like you are going to faint or something.  Even though it is not your style, ultimately it's counter-productive for him.  If I didn't scrap with him, he would still be completely lost like he was at the beginning of this thread.  Direct talk sometimes has its merits.

The only one here that is lost,is you MH,and that has been made apparent time after time.
You just cant handle the fact that i have been told by the top guys here ,that i am correct,and you are wrong.

In the final end game, if Brad is going to have his crazy theories, live and let live.  It's just a chat forum.

The only crazy here,is you MH.


Brad