Transformers
Transformers work this way: An AC voltage:
VAC-1 = V1 sin(wt) , is used to generate a current: IAC-1 = I1sin(wt) in coil #1 which generates an oscillating magnetic field in coil #1 since B is proportional to I: BAC-1 = B1sin(wt); a second coil (#2) is inside coil #1; this #2 coil then, by Faraday’s Law, DV = D[ (N B A cos(qBA) ] / Dt
has a voltage, VAC-2, induced in it. By adjusting the number of loops in both coils, the induced (AC) voltage in #2 can be different than that in coil #1. We can adjust (or transform) the voltage up or down!