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?

It's  like i said MH , there is a big difference between having a small amount of resistance,and none at all. It is the difference between having a time constant,and not having one.
It is the difference between having a current trace curve over time,and not having one.

It is the difference of having water at 1*C and ice at 0*C

Brad

 
I have no clue what you really mean when you talk about "opposing current generated by the CEMF."  The CEMF does not generate any current.  If R = 0 in an ideal setup the current will rise indefinitely.  This has been covered already.

If there is a small amount of resistance vs. no resistance at all, and you evaluate situations where the time frame you are examining is much less than the time constant, then there will be negligible differences in the current for the two setups.  This has been covered several times already but I suppose that it did not stick. 

This is exhausting, going over the same material over and over.

MileHigh

 
I have no clue what you really mean when you talk about "opposing current generated by the CEMF."  The CEMF does not generate any current.  If R = 0 in an ideal setup the current will rise indefinitely.  This has been covered already.

If there is a small amount of resistance vs. no resistance at all, and you evaluate situations where the time frame you are examining is much less than the time constant, then there will be negligible differences in the current for the two setups.  This has been covered several times already but I suppose that it did not stick. 

This is exhausting, going over the same material over and over.

MileHigh

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

...

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.

Tinman,

You should research superconductors a bit.   

It's a huge field to weed thru, but there is both normal inductance (L) and kinetic inductance (L_k) associated with superconductors.

The kinetic inductance, L_k allows for operation up to and into the THz region and is exploited in radar components, such as antennas and phase shifters.  L_k allows low loss superconducting stripline techniques to be used rather than traditional and bulkier waveguides having more loss.

At lower frequencies where normal inductance applies, an 1800 RPM, 1MW, portable generator was constructed as a power source for a mobile radar system that uses superconductors in the rotor windings to reduce the generator's size.

Thousands of superconducting electromagnets (i.e., inductors) are in use everyday all over the world.

The field of zero resistance electronic components and specialized sensors is also a rapidly growing and heavily investigated field.

And then there is energy transport and storage, the list goes on...

You may argue that man made superconductors do not have a DCR of exactly zero.  In some cases that may be true, particularly with respect to high temp SC's.  Their resistance can range from 10^-9 to 10^-18 ohms of directly measured or calculated resistance.  However, some low temp SC's, which were believed to be less than 10^-28 ohms, the limits of measurement resolution (directly or by proxy), have since been measured by way of some rather unique methods that indicate they do indeed possess zero ohms of resistance. 

The point I am making is that zero DCR inductors (and other components) are in use everyday all over the world.  If an inductor made from a zero DCR conductor behaved as you propose, surely that would be a commonly known phenomenon by now.

Just food for thought...

PW

You can accept it or not, but the actual reality is different and NOT covered in any textbook due to lack of need, and basic understanding.  2 other PhD's agree with me, but then quoted me one of Murphy's laws.  "Never argue with a fool, people might not know the difference."  In the context of this situation, they say I am the fool for expecting someone else's viewpoint to be even close to mine.

We know, the books are running years behind the ICE Tuning-Ateliers, this since years, the tuning Software even more, sorry!

With a Overlay in Exhaust and Inlet of a ICE, its a Serie-Cavity-Resonator, piece of Sheet-Metal called ........ is just a small part of the complete phenomena, what is almost not to catch in language its a understanding / knowing called Resonance, harmony and missing here grotesque!

To talk whit bookies, you have to talk there bookies-slang, other language than "The Haempstead" slang they don't willing understand.

OU is most dominated by RosaGlass-Followers, thinking they are in the lead, but out of compensation, and missing the best out of ........................ because of Dunnig-Kruger with a teacher syndrome!

Building NO.7!
Chemtrails!
Nasa!

Don't think, we do it for you!

Cheers

Which leads back to one of tinmans statements that : 'the emf must be greater than the cemf for current to flow', with my added caveat - 'in a real inductor.'

Yes-for real(non ideal) inductors,we know this is true.

What will happen in an 'ideal' inductor is great debating material, however, almost all explanations could be considered equally valid simply because the ideal doesn't exist (except possibly - inductors made with superconductors?) and therefore any hypothesis relating to it is (currently) unfalsifiable. But 'ideal' hypothesis do give the brain matter something to chew on.

Indeed--what will happen?
The question deserved a better look than it go.
Instead of this being a thread to discuss the question as presented,the thread turned into a !!MH must be correct!! thread.
The mere fact that the coil has no resistance was in it self,worthy of a closer look. But it was just discarded,and so we removed the time constant from the equation,and went to plan B to find an answer.
We already know that the CEMF is what stops the current flowing through the coil,from shooting straight up to it's maximum value for that coil.
We also know,and have agreed on,that the current flowing through an ideal coil,with an ideal voltage across it,will rise in a steady state of increase for all time.
This can only mean that the magnetic field is changing at a steady state as well,and there for,the CEMF produced by that magnetic field will also be at a steady state.
So what dose happen from T=0s ?
Well,that is yet to be worked out,but i can tell you that it will not be the answer MH believes it should be,and that is the very reason that i said that i could(and did) provide the answer he wanted to see,but that i did not agree with that answer,or the equation used to get that answer.
The fact that the time constant is infinite,dose not just mean you dismiss it,and move onto another equation to derive at an answer you want to see.


Brad

Loner
Quote

Take an "Ideal" voltage source, of any value.  Connect to "Ideal" switch of SPST design.  Connect this to an "Ideal" inductor.  I hope I have not lost anyone, yet.  This is for the "Minds" eye, as such components don't actually exist.  Close to these "Ideals" is of no use in this explanation, just as 0 is 0, not some infinitely small number...
 If the switch closes at Time = 0, as was mentioned here by someone, what is the situation that is REALLY happening.  ( Common sense applies here, try to stay in the minds eye and remember "Imagination is more important than knowledge" )
 At t=0, you have a voltage "appearing" at the leads of the inductor, before current has started to flow, and therefore BEFORE the CEMF has been generated by self inductance.
 If someone wishes to argue that the current would "instantaneously" appear, then you wish to state that a current can appear that way in an inductor, which violates the "Laws" of an inductor.  You can have it both ways at the quantum level, but not at the macro scale.
 THIS is one of the errors in current thinking and math, because as t increases, the current increases.  as current increases, it is the "Rate of change", NOT that actual amount, that is producing the CEMF.  Again, if the CEMF were EXACTLY equal to the applied EMF, the "Rate of change" would be equal to 0, which then forces the CEMF to also drop.  I am ignoring ALL external influences here.  We ARE NOT talking about a wave or cyclic event, just the initial magnetic charge from 0.  To put it another way, simply try to see HOW a totally empty inductor, with NO field, can produce any CEMF.  There IS NONE UNTIL the current flows.  It's not even a "Chicken and Egg" idea, it is just the reality.
 Are we there yet?  I am NOT talking about a large difference, nor could anyone on this forum (I'll wager...) say with absolute certainty WHERE that difference could be measured,  Even if you used real circuit components, this Micro difference exists.  It is how much of the math could be easily derived, as a figure so low can easily be ignored for any realistic calculation of components or values, but to blatantly state, "It does not exist" is to deny reality and common sense for people like me.
Snip
You can accept it or not, but the actual reality is different and NOT covered in any textbook due to lack of need, and basic understanding.  2 other PhD's agree with me, but then quoted me one of Murphy's laws.  "Never argue with a fool, people might not know the difference."  In the context of this situation, they say I am the fool for expecting someone else's viewpoint to be even close to mine.
end quote
----------------------------------------
It was good to read all your contributions over the years , Thanks for all the work you shared and the level headed mindset
you brought along with it.

Loner has deleted all his posts and his acc't [or it will be shortly]

A sad day indeed.

ChetKremens@Gmail.com

Loner has deleted all his posts and his acc't [or it will be shortly]

If you look at his profile, he has 994 posts, so no I don't think he has deleted any of his posts.

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

It's like you have regressed and you are back to some kind of whackadoo "Great Pumpkin" fantasy.

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.

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,the current produced by the CEMF ,is less than that of the induced current by the applied voltage.

I can't see anything.  I thought the current was -75 amps at the start.

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.

I am totally confused.  I tried every setting on my secret decoder ring and it's not able to unscramble what you are saying.

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.

It's like you have completely regressed and this entire thread never happened.

Listen, when you apply voltage across a coil, the coil integrates the voltage with respect to time and the result of the integration is current flowing through the coil.  It's like pushing on a shopping cart.

If the coil is a real coil then you have to account for the resistance.  Then it becomes a slightly more difficult problem.  Using standard mathematical techniques you solve for the circuit and you get the standard exponential equation that we all know that with a tiny bit of algebraic rearranging of some variables gives you a nice convenient time constant to work with.

That's all there is too it, a coil integrates on voltage to give you current just like a shopping cart integrates on force to give you velocity.  It's just Mother Nature in action.

All of the stuff in your head about "battling currents" is a model that simply does not work.  It's crazy talk.  It's like something that you found in a pumpkin patch.

MileHigh