MH's ideal coil and voltage question

[Magneticitist]

Because the current produced by the inductor is equal and opposite to that being provided by the ideal voltage source,and so no current flows,but it dose rise to an infinite amount.



I have asked this question before--what happens when an unstoppable force meets an unmovable object?.


Brad

right, in that scenario it could be said there was never any current at all. infinite is the same thing as none at all in practice.

however, if we were to assume this infinitely rising current without any curvature continues to infinity, that in itself is a current change, therefore how can it be function as an ideal coil? In the very nature of how its operation is described it seems as if it should be infinitely resting with 0 current flow or infinite current flow.. which as I say is the same thing so we might as well just say none at all.

[allcanadian]

@Magneticitist

I don't see why we should have to take it further than "perfectly and absolutely resists current change".  This automatically means no EMF or counter EMF doesn't it?

An Electro-Motive Force relates to electric fields and a Magneto-Motive Force relates to the Magnetic fields. The Electric field is the cause or the source of the force which initially acts on the charges causing them to move... a current. If a charge tries to move it instantly produces a magnetic field which opposes it's motion which we call a Cemf. We call it a Cemf because the conductor contains billions of (+) and (-) charges and the moment one tries to move the rest oppose it because they are linked by electric fields.


So yes the Emf is present as an electric field of force... before... anything moves such as a current. The Emf is the cause of the current not vice versa.


@Picowatt

This would more so describe an ideal inductor that also has an infinite amount of inductance.  As such, when connected across a voltage source, no current would ever flow as the time constant would also be infinite.  An ideal inductor with infinite inductance would appear to be a continuous open circuit when connected in parallel with a voltage source.

First we should ask what is inductance?, Inductance: the property of an electrical conductor by which a change in current through it induces an electromotive force in both the conductor itself and in any nearby conductors. Inductance is not something but a property of something which is actually self-inductance which relates to a Cemf. So when we say Inductance what we really mean is self-inductance or the generation of a Cemf which opposes the source Emf.


In this case we are speaking of an Ideal Inductor, a perfect inductor with no losses of any kind hence the term "ideal". Now if a charge tries to move it must instantaneously invoke an equal and opposite Cemf because we have defined action and reaction occurring under ideal conditions, no losses. Thus any inductance (self-inductance) of any kind in an ideal inductor qualifies as infinite (however not an infinitely large field) because the term inductance relates solely to the Cemf which must oppose the source Emf. An ideal closed loop superconductor produces a continuous current at zero voltage and an ideal closed loop super-inductor should produce a continuous electric field opposition or Emf/Cemf at zero current. Can you see the symmetry here?.


I know this seems difficult to understand because this leads to questions which many find deeply disturbing. What is an Electric Field, what is a Magnetic Field fundamentally?. You see it's like trying to describe a bike without knowing what a wheel is. This is why everyone tends to throw about terminology never knowing what the terms actually mean or what they are supposed to describe in reality.


AC

[Magneticitist]

@Magneticitist

An Electro-Motive Force relates to electric fields and a Magneto-Motive Force relates to the Magnetic fields. The Electric field is the cause or the source of the force which initially acts on the charges causing them to move... a current. If a charge tries to move it instantly produces a magnetic field which opposes it's motion which we call a Cemf. We call it a Cemf because the conductor contains billions of (+) and (-) charges and the moment one tries to move the rest oppose it because they are linked by electric fields.


So yes the Emf is present as an electric field of force... before... anything moves such as a current. The Emf is the cause of the current not vice versa.


@Picowatt

First we should ask what is inductance?, Inductance: the property of an electrical conductor by which a change in current through it induces an electromotive force in both the conductor itself and in any nearby conductors. Inductance is not something but a property of something which is actually self-inductance which relates to a Cemf. So when we say Inductance what we really mean is self-inductance or the generation of a Cemf which opposes the source Emf.


In this case we are speaking of an Ideal Inductor, a perfect inductor with no losses of any kind hence the term "ideal". Now if a charge tries to move it must instantaneously invoke an equal and opposite Cemf because we have defined action and reaction occurring under ideal conditions, no losses. Thus any inductance (self-inductance) of any kind in an ideal inductor qualifies as infinite (however not an infinitely large field) because the term inductance relates solely to the Cemf which must oppose the source Emf. An ideal closed loop superconductor produces a continuous current at zero voltage and an ideal closed loop super-inductor should produce a continuous electric field opposition or Emf/Cemf at zero current. Can you see the symmetry here?.


I know this seems difficult to understand because this leads to questions which many find deeply disturbing. What is an Electric Field, what is a Magnetic Field fundamentally?. You see it's like trying to describe a bike without knowing what a wheel is. This is why everyone tends to throw about terminology never knowing what the terms actually mean or what they are supposed to describe in reality.


AC

thanks for the explanation.. but I'm not in disagreement that EMF is the cause of the current. I'm saying I don't see how there would be any current, EMF, CEMF, or any kind of interaction I would consider a Lenz Law interaction that would require more current to overpower an equal opposition.
That would be the scenario I see played out were current actually flowing into this inductor with infinite rise time and no curvature.

but I personally can't get past the sheer logical aspect of the argument. I don't see the need to have to get into the complex details of charges and opposing forces when the ideal coil is said to no dissipate energy and perfectly resist change in current. I don't see how that doesn't imply no current at all, unless we are approaching this imaginary scenario adding the parameter that this ideal inductor is already partially charged and just accept that as imaginary scientific parameters.

[verpies]

There's a lot about inductors and it's very basic and even I've been able  to inch forward, albeit very slowly.

Did you discover yet, that inductance is the amount of magnetic flux that is generated by a given electric current ?
In other words, Henry = Weber / Ampere.

[picowatt]

Thanks for joining PW.
I have to say that i dont agree with the ideal inductor needing to have an infinite inductance value.

An ideal inductor does not have to have an infinite inductance.

What I said was your description of an inductor whose EMF and CEMF are in perfect balance would be descriptive of an inductor with infinite inductance.  An inductor with infinite inductance, when connected across a V source, would forever appear as an open circuit.

It is hard for some to understand what !ideal! mean's,but think about it long enough,and you begin to put all the pieces together.

A straight length of ideal conductor, such as a straight wire with no resistance or capacitance, would be an ideal inductor.  Just like its less ideal real world counterpart, a finite amount of time is required for current to flow thru the wire because of the wire's inductance.

Wrapping that same straight length of ideal (or normal) wire into a helix increases the coupling between sections (turns) of the wire and increases its inductance.

I do not understand why you believe that an ideal inductor would cause an instantaneous and infinite amount of current to flow when connected across a voltage source.  As I said, that would be more descriptive of an ideal capacitance.

Gotta' go...

PW