Does magnetic resistance cause electrical resistance in a coil?

[mbrownn]

As I understand it, BEMF is an electrical voltage that is generated in a wire or coil of a motor that opposes the current and voltage powering the motor.

any wire or coil passing through a magnetic field will have EMF generated in it in exactly the same way as BEMF is generated

If the magnetic field, or the wire are not moving in respect to each other, there is no current

Any current passing through a wire generates a magnetic field

If a magnetic field is building or collapsing it will generate emf in a wire in that field

Of course any movements of currents generated in a wire in a magnetic field will have a magnetic interaction with that magnetic field

It is argued that inductive kickback is generated by field collapse; however that does not explain the transient voltage spike spike that occurs at the moment of collapse

My explanation is as follows. When an electron enters into a wire we create a negatively charged pole. By the Laws of attraction, anything positively charged will be attracted and anything negative will be repelled. When that electron leaves, the wire is for a moment, charged positively by what has been attracted and so the reverse law of attraction happens. It has been proven by experiment that some of this positive charge can be used to charge batteries and capacitors but yet little or no current flows. This is a second source of energy to be found in a pulsed coil. This must not be mistaken for the inductive kickback caused by the magnetic field collapse. Inductive kickback cannot be of a higher potential (voltage) than the power that created it. The higher voltage measured on inductive kickback is actually this second input. It is only momentary spike whereas the inductive kickback lasts a much longer period of time and has current. If you have a better explanation please tell me.

[Shadesz]

This post is long, but it should help you understand what I am asking about.

The way I see it, back EMF only occurs in coils where the applied electrical current is changing.

If you start talking about a magnet and a generator coil, back EMF no longer fits as the correct terminology. The term switches from back EMF to the negative half of the generated AC current. Note: many people on public forums use the Bemf term incorrectly in this manner.

Per my current understanding, real BEMF goes like this...
The magnetic field in a coil does not necessarily want to remain at 0 charge. Instead, it wants the magnetic charge to stay in equilibrium with the electric current going through the coil. Magnetic charge = electrical charge (this should makes sense)

Because of this desire for equilibrium, when you first introduce a current through the coil (while it has no magnetic charge) the coil will resist the electrical current that you applied. Note that this initial resistance only occurs as the magnetic field of the coil is growing to match your input current. Once the magnetic field reaches a charge that is equal to the input electrical current, it reaches equilibrium and no longer tries to resist this electrical current.

During this equilibrium time, if the input current remains constant, the magnetic field in the charge coil acts as a passive capacitor. It sits there wanting to collapse once the applied electrical current is removed. Once that current is removed, the magnetic/electric equilibrium in the coil will be out of balance, and the coil will do two things to correct this. It will shrink its magnetic field (the field will collapse) and because of that collapse, it will create an electrical charge in the wire.

However this electrical charge wants to go in the opposite direction of the initial applied electrical current. Hence it's name, Back EMF. Based on your circuit, this back charge will dissipate as quickly as possible. This is why on most circuits, it is seen as a voltage spike. There are circuits out there that claim to reduce the speed of this back current by using a diode that limits the maximum voltage.

Anyways, YES, the charge-up of a magnetic field in a coil acts as an electrical resistor. So for a limited time, magnetic current acts as a resistor to electrical current. This electrical resistance only occurs until the coil and magnetic current are at equilibrium. Once at equilibrium the field is no longer changing and thus the electrical resistance diminishes. The magnetic charge then sits there waiting to release its stored energy. Once no more electric current is pushing through the coil, the stored energy in the magnetic field returns to electrical current as the field collapses. This current is in the opposite direction of the original current. (It's the BEMF spike)

Think of it like this. You push a stroller up a hill by using an electrical current. As you are actually moving the stroller upwards it takes more energy. This extra energy is manifested by electrical resistance (the stroller's resistance to moving uphill). The higher the stroller goes, the more energy is required. Eventually, you reach your energy peak and can't push the stroller up any higher. If you keep your electrical current applied, the stroller will remain in the same place. However, once you stop your current, the stroller will want to roll back downhill. As it does it will create a backwards current in your circuit because of its backwards motion. The backwards stroller motion and thus backwards electrical current will happen as fast as your circuit will allow. Does that make sense?

I'll get to explaining my question soon. But let's review one more thing. How does Back EMF relate to a steady DC motor? Note: this will be a little different that a pulsed drive coil, but it will still help us understand back EMF. I found this good explanation.

In short, the current a motor consumes, is proportional to the applied voltage minus the induced Back EMF.

Back EMF is simply a voltage induced in a motor's armature, as a result of it spinning in its own magnetic field ...the same way a generator works. This voltage is induced in the opposite polarity of the operating voltage applied to the motor, and thus tends to impede [or resist] the current flow caused by the applied voltage. This is why the "stall current" (the motor current that occurs when the armature is prevented from turning) is far higher than running current. The faster the armature turns, the greater the Back EMF, and the more the Back EMF, the more the motor's operating current is opposed and reduced. [over-simplified, this is because at higher speeds, there is more switching on and off, hence more back spikes and more resistance because your are continually trying to rebuild the field]

The above action explains why a typical motor has its maximum torque at zero RPM (where no BACK EMF can exist, and thus maximum operating current will be drawn), and that torque linearly falls as speed increases (because Back EMF linearly increases as RPM increases, thus reducing operating current).

If a motor had absolutely no frictional losses at all, then your statement that "the max velocity of the motor occurs when the Back EMF is equal to the voltage across the motor", would be true. In the real world, however, motors have friction to overcome, and loads to drive. So in reality, a motor will increase its speed, increasing its Back EMF and reducing its current drawn as its speed goes up, until a balance is reached and the current it uses generates just enough power to overcome friction and load. At that point, the motor no longer accelerates and its speed remains constant.

My question...
Ok, we have pounded that point to death. So now we know that as your electrical current charges the magnetic field in a coil there is actual electrical resistance, and once we remove that current, the extra work it took us to charge the coil is then release backwards through the circuit. Now for my question.

If you have a permanent magnet already influencing the coil opposite the pole you are going to induce, how much magnetic field will the coil have to build in order to reach equilibrium with the electric current going through it? Will it have to negate the PM field before it can build its own field (this would require more energy to build the field thus you would get more electrical resistance) OR, does it only build a field strength that relates the PM field to the electrical current and doesn't build it any bigger than that?

In one sentence, if you induce a magnetic field in a coil that is being influenced in an opposite pole with a permanent magnet, will it require more work for that coil to reach magnetic/electric equilibrium?

[mbrownn]

I don't know is the short answer, but what I can say is that in a motor you do not have to create a big or powerful field to make it work. All you have to do is create an imbalance, the amount of field required is enough to negate the permanent magnets attraction to the armature and a little more for torque to occur plus overcome friction. With a coreless motor you don't have to overcome any attraction so you only have to overcome friction to get the motor turning.

A motor works by creating an imbalance. You do not have to equal the permanent magnets field.

Remember that resistance and impedance are different, I think you mean impedance.

I think your explanation answers your own question, the magnetic field will create an impedance during field build up but once that has been done you are back to ohms law for current. It makes sense that if you double the field of the magnet you will double the energy required to overcome the impedance in a given coil but I could be wrong. My question is how is inductance effected by magnetic field strength? If I am right then it is increased proportionally. again if I am right capacitance and impedance will increase too but I don't know.

I think we both need the same thing answered.

[SuperCaviTationIstic]

remember Tesla patented a way of rectifying current with an inductor wrapped on a permanent magnet.
Tesla Patent 413,353 - Method of Obtaining Direct from Alternating Currents

[Joit]

Magnetisem can be converted into electricity and so can light, but light does not interefere with or help conduct electricity. You've seen enough wireless examples of electricity on youtube. The trasmission of elecrtrc current is not influenced by the presence or abscence of light. Light, electricity and magnetisem are seperate but related forces along with gravity. Now gravity's another thing, and influences the other three forces. Even though they're interchangable, they fail to influence one another. It does nothing to hold a magnet up to a wire conducting electricity. Put a loop in the wire, and it transforms into magetisem. Conversely, magnetisem does nothing to interfere with or help conduct electricity, but pass the field accross the wire and it transforms into it.

Gravity is actually a Result from a spinning Medium, therefor its a Effect, not a Cause.
Same for Light, Light is created througth Resistance or any other Influence.

I stay with pure Magnetism, because it makes even Sense, when you consider Magnetic Areas in Crystals, where they align, and lead a Magnetic Field.
Like a Core can lead Magnetism over a long distance, so you can do that with a lot small Magnets with a turnable Attachment, what align in a Domino effect.
Any Souces we are producing Magnetism comes from Magnetism first.
The Electrostatic Charge is there no exemption, because you have 2 Bodys what have seperate Charges.
Therefor there would no further Medium, like Electricity or her so called Electrons be needed to transfer a Force.

For the BEMF it is difficult to control it, figure a (Sine)Wave, in a Channel and a surfboard infront of it.
The Load is infront from the Wave, putting a Resistance on it, like turning the Board sideways requires more Power to move the Main Wave.
You could break the BEMF when you decouple the Load at the strongest Moment, but it is more like a pysical Resistance then a induced Resistance.

[nueview]

i think you guys did a great job of going over what is in every text book and it is as clear as mud.

there are so many contradictions and energy does not work like that emf is not mmf and yet you guys keep wanting to make an e-field part of the b-field and h-field

you discuss apples and oranges as if because they are both round there the same and there not and i have seen enough to know better and so have you.

i can't say i understand it all but i know enough to know this is not right.

Martin

[Shadesz]

i think you guys did a great job of going over what is in every text book and it is as clear as mud.

there are so many contradictions and energy does not work like that emf is not mmf and yet you guys keep wanting to make an e-field part of the b-field and h-field

you discuss apples and oranges as if because they are both round there the same and there not and i have seen enough to know better and so have you.

i can't say i understand it all but i know enough to know this is not right.

Martin

What is it that you suggest isn't right? I asked the question because I am trying to understand. How do you fell I am off target? What am I making more complex than it needs to be? Thanks in advance.

[nueview]

to all
i can say i am making the same mistakes as you all are making as well i was clasically trained for electronics and it is an impedement to me at times so i am against no one here.

i have a motor that self runs when it is turned off the only difference in it is a spark arcing to ground it is a standard induction motor and i have been working on it for ten years.

my problem is i keep putting it back to what i have been tought in electronics and everytime i do it fails.

a few weeks ago i did something i know to be all wrong for these motors and somehow i got it all upside down and the results were very interesting.

i was given a bunch of papers by eric dollard and it seems he is going along the same way this motor does as well.

i can say that most of the power in a motor seems to have a magnetic base and its flow is were we find resistance as it does not seem to propagate well without a metal path per say.

on the other hand charge seems to be very content at passing its potential along unlike magnetics the fields are different and the actions are not the same and the interactions are confusing even to me charge potentials seem to know how and were to go by there very nature and will go opposite and or with a magnetic field but they seem to follow there set of rules reguardless of the magnetic.

the magnetic also have there rules and do not deviate as well so within a system one can have magnetic fields aiding and charge e-fields canceling as dollard says and then all the vectored derivitaves as well.

this makes much more sense and is much like what i am seeing and when it is all vectored correctly it seems to grow in total potential but yet it seems to have a balance point as well.

i have a few static machines i have killed by working them in different ways as well the materials seem to become very brittle and stop moving charge more like plastic becoming stone were the metal charge carriers insulate themselves off from each other.

i see this effect in tesla coil demonstrations as well and also with hairpin circuits as well as with certain other oscillating circuits and i do not have an answer as to how or why but i know it is not as i was told in the books or as you guys went through above.
Martin

[Joit]

Nueview
talking about Vectors, when you figure each Coil as a more or less flat Field, would it help to figure, how to align them and drive them seperate?
I still figured out, that a Coil can have a sweet spot at 90° or 120° from its axle, depends on the direction from the Wire, cw or ccw and the Pole, what is passing.

[nueview]

i think some things about field action need to be cleared up before we can go to far if i say emf some of you may think i am talking electromagnetic force for me this is a butcher explanation.

if i say emf i mean electro-motive force it is separate of the magnetic or mmf for magneto-motive force and yet as don smith says they are interconnected but more like dollards magnetic to dielectric and back to magnetic.

the problem seems to be in the difference between the two and any real power seems to come from the proper alignment of the different fields so let me try to explain a bit.

lets say we start with a low Q tank circuit and have a magnet at one end of the coil and the magnet is 90* to the coil if the magnet is turned so the south end is to the coil the charge is driven to the far end of the coil and stored as a dielectric charge on the capacitor and as the magnet crosses top dead center the field begins to drop and charge begins to neutralize across the capacitor this forms a magnetic field in the coil driving off the south pole and attracting the north pole of the magnet and starts stacking the charge on the capacitor on the plate nearest to the magnet end of the coil there is never a back emf in the phase shift as the magnet goes 90* to the coil there is no dielectric charge present until the north pole crosses top dead center again.

the capacitor cancels the back emf as for charge close is good enough across the dielectric. so the emf and mmf are running synchronous at a 90* phase shift.

this is a true relationship as long as the magnet is not dropping in speed and remains synchronous field relationship with the tank circuit.

now lets remove the capacitor and replace it with a resistor and start through the cycle again the magnet is 90* to the coil the south field is turned to the coil and it pushes the charge to the far end of the coil through the resistor and back to the near magnet end all the time that the south end is relating to the coil the charge is accelerated going in and when coming out it is decelerating the field in the coil while leaving it so there is a breaking force applied.

as the magnet goes 90* to the coil again and the north side is coming into the coil it repeats the cycle again but in the opposite direction.

in short the dielectric phase has been removed from the cycle so there is a difference.

if the coil is open and the coil field is only allowed to build potential then the charge required is small and filed action is minimal.
Martin

[Allen Burgess]

remember Tesla patented a way of rectifying current with an inductor wrapped on a permanent magnet.
Tesla Patent 413,353 - Method of Obtaining Direct from Alternating Currents

The magnet and the inductor flux field interact in these inventions. The magnet field has no direct influence on the current in any of Tesla's circuits.

[nueview]

@ allen
i do not see yor reply as valid that he is stating that the E fields can be caused to move in conjunction with different properties of the magnetic action is ok and demonstrated but it is not assumed that the magnetic is not present.

martin