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

[sm0ky2]

Simple things like what that profesdor told me: current will always flow from a high potential to a low potential.

This is true in a broad sense
But as it pertains to back-emf, you have to take the whole situation into perspective
Where is your potential?


Faraday's law of induction states that the reverse emf is of Opposite polarity to
the change in current.
This means the current is in the Same direction as the inducing field
And the voltage is of Opposite Polarity.


The current does not reverse directions!

[tomd]

I think allaboutcircuits offers a good explanation.

I find the thing you have to keep in mind is that the coil is the source when the magnetic field is collapsing and in order for the current to not change direction the voltage across the coil must change polarity.

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/inductor-commutating-circuits/

[Magluvin]

I think allaboutcircuits offers a good explanation.

I find the thing you have to keep in mind is that the coil is the source when the magnetic field is collapsing and in order for the current to not change direction the voltage across the coil must change polarity.

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/inductor-commutating-circuits/

Pretty much what I just said in my last post..  Also some books on switching power supplies are a great reference also.

Mags

[sm0ky2]

I expect you'll bend the knee and kiss the ring if I am awarded?

more likely that I will just assimilate your enlightened knowledge

[sm0ky2]

Sometimes it's just a matter of perspective
or rather putting things in their proper perspective


Like, for instance a battery
You have a potential, and it is capable of producing some current
it has an internal resistance, which prevents the (+) from just
going through itself to the (-).
So when we connect it to our coil, the current runs through the coil
around to the battery's (-).


Now we have a coil, (let's assume we just switched it off)
It has a collapsing magnetic field, which induces a potential
This is parallel to the source now (opposite polarity)
Our coil has very little internal resistance
So the current runs through the coil from its (+)
to its (-).


In both cases, the current runs through the coil in the same direction.
The current takes the path of least resistance.
Which is through the coil.