And I mean what is happening on an atomic level that is not happening with DC so that induction can occur? I’ve been doing a lot of reading to wrap my head around it but I can’t seem to get an answer that explains what is happening throughly, just a lot of “just because”. What is going on with the electrons that allows them to transfer over to the second coil that does not occur with DC?
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Electrons do NOT move from the the primary to the secondary (unless you are talking about an autotransformer). There are in fact transformations intended to solely provide power to the secondary without a galvanic (wire) connection (isolation transformers). Transformers connect circuits through magnetic and not electric coupling.
A constant current generates a constant magnetic field. DC by definition has a constant voltage which will produce a constant current. It should be noted that a DC circuit will not always have a constant voltage or current, but the frequency content is usually not very high for most linear circuits.
In the simple transformer the primary is coils of wire wrapped around one side of an iron loop. Closely coiled wire is what is known as a solenoid, and generates a relatively constant magnetic field on the interior of the loop whose strength is proportional to the current flowing in the wire.
The secondary is another solenoid wrapped around the opposite side of the iron loop. Since both wires are insulated there is no direct galvanic (electrical) connection between the two solenoids.
With AC, the current flowing through the primary generates a magnetic field that varies with the varying current. Iron (and other ferrous materials) operate as a kind of wire for magnetic fields. The changing magnetic field originating from the primary travels through the iron core and through the secondary coil. Just as a changing current creates a changing magnetic field, a changing magnetic field will induce a current to flow. Thus a changing current is created in the secondary.
Since DC does not have a changing current it cannot create a changing magnetic field and thus a transformer will not work with a typical DC circuit. It should be noted that the iron core is not strictly necessary, and they do make air core transformers, but the iron core greatly increases the magnetic coupling between the primary and secondary.
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