I want to generate a magnetic field from a coil made of copper. Let's consider a simple circuit with a power source (12VAC), a transformer and a coil.
I always see that step-up transformer increases the voltage and reduces the current while a step-down transformer increases the current and reduces the voltage because the power is conserved (P = VI). Since the magnetic field depends on current, I guess I should use a step-down transformer.
However, the coil has some resistance. So if I use a step-up transformer, I could generate a really large voltage across the coil and the current (I = RV) would also be large.
From my understanding, the current is dependant on the load following Ohm's law. If I use a step-down transformer, the voltage across the coil would lower and the current would lower as well. So I don't get why we say that step-up transformer (or a buck converter) would increase the current if it's decided by the load and the voltage across it and the power is conserved.
The way I see it is that the 12V is fixed at the primary. I feel like I'm missing something, please correct me if my understanding is wrong.