Back-EMF Manifesto - A Key, hidden in plain Sight.

[forest]

Someone should confirm it Magluvin. Proof is simple but a long core is needed. If indeed flux is passing in center hole of core then the secondary could be very loosely wound on the opposite leg of core and still get more induction then in the same arrangement of coils without core.

[tinman]

Someone should confirm it Magluvin. Proof is simple but a long core is needed. If indeed flux is passing in center hole of core then the secondary could be very loosely wound on the opposite leg of core and still get more induction then in the same arrangement of coils without core.

Yes,a loosely wound secondary will produce an EMF across it-->but it is not the magnetic field that is the cause of this EMF across the secondary.


Brad

[partzman]

Now, very quickly as I have a job to work on tonight, below is how I see the way mag fields engage the core of a toroid or any closed loop core and how the fields of a say primary winding on the left side of the core can 'cut' a secondary on the right side of the core. All the action is in the hole of the core, other than leakage on the outer sides. So no, I dont believe that the mag field is only in the core.  The core is only a path material that allows the fields to come together and be able to make sharp turns, etc.  When we look at the field mushroom out of the end of a magnet, those like fields repel and are pushed outwards away from one another. A magnetic core 'helps' to negate or better to say, reduce that like field repulsion that happens outside a magnet or a core and allows the fields to be denser and to bend and turn in the cores path much much easier than when the fields are outside the magnet or core. That is my contention on that subject.

Mags

One of the best papers I've found on this subject which closely agrees with your analysis is attached below.  The authors Edwards and Saha have done much bench work and theoretical analysis on the S flow or power flow in wire, coils, transformers, capacitors, and even including core flux diffusion.

Regards,
Pm

Edit:

[sm0ky2]

Tinman is right


The current will flow in the direction of the inducing current
But the voltage potential in in the reverse direction.


It may be easier to think of it as a series-parallel configuration
For instance, in a simple case of:
a voltage source (battery),
a switch
and an inductor (R)


When the switch is closed, the inductor voltage is in series.
(-) facing the (+) of the battery, (+) facing the (-) of the battery.


when the switch is open, the inductor voltage is in parallel
(+) facing (+), and (-) facing (-).


Current is in the same direction as the closed circuit.

[sm0ky2]

What is interesting is when you saturate the coil with magnetism rather than inducing current


In this case, the direction of current of the collapsing field is determined by the direction of winding.
it will follow left/right hand rules, respectively.


This is because of the c dependency of electromagnetism
which is not present in permanent magnetism.
(Einstein's relativity doesn't allow for greater than c interactions)