How does the core material affect a transformer? Such as if you use steel vs. air. Or wood vs. magnet.
A transformer is a gadget that converts an alternating (A/C) modern of a definite voltage to an alternating modern of diverse voltage, without substitute of frequency, via electromagnetic induction. A 'step up' transformer gets a low voltage and converts right into a miles better voltage, and a 'step down' transformer does in basic terms the opposite.
In 50 or 60 Hz transformers putting in a laminated magnetic iron core greatly increases the amount of magnetic flux which is generated by the primary current with the secondary on open circuit (the so called magnetising current). This enables the windings to generate a relatively high voltage with relatively small magnetising current. If you tried to make a 50/60 Hz transformer without a magnetic core (with say air or any other non-magnetic insulating material) it virtually wouldn't work because the magnetising current would be so high (the primary winding practically a short circuit). If you used a non-magnetic conducting material you'd be even worse off because eddy currrents generated in the material would prevent any flux being established and you'd have plenty of core heating but no coupling between primary and secondary. For this reason even the iron core must be laminated (unless it's non-conducting ferrite). The story is quite different for high frequencies where the inductive impedances of coils are enhanced by the frequency. There you can make quite effective air cored transformers; small ones at least - but you'd still better avoid conducting material in the core - that's what food is in a microwave oven; conducting material in the core of a high fequency transformer.
