# How do I create an AC electromagnet for a particular type of field generator?

I’m trying to generate a special sort of field in a spherical spinning iron core using two orthogonally oriented coils.

One single-layer coil of 18 AWG magnet wire is wrapped directly onto most of the surface area of the 1” iron sphere that is to be spun, with its direction perpendicular to the spin axis. Some commutators and brushes will be used to deliver direct current to this coil. I’ll refer to this as the rotor of the field generator.

Another single-layer coil of 18 AWG magnet wire is then wrapped onto a fixed hollow spherical shell (not much larger than the rotor, let’s say it has an OD of 1.5”) surrounding the rotor, with its direction parallel to the spin axis. This is the stator.

What is the easiest/simplest/cheapest/most reliable way to go about supplying an alternating current to the stator coil? Getting an exact frequency and amplitude aren’t a concern, as I can simply tune the spin frequency/wattage of the rotor coil to match. But of course ensuring the amplitude is low enough to not damage anything is important.

• Is direction along the axis of a coil (of parallel windings?), or along its conductor? Commented Apr 20, 2023 at 20:44
• @greybeard Direction refers to the axis (length) of the coil in relation to the spin axis of the iron sphere. Commented Apr 20, 2023 at 20:48
• So the direction of the length of the rotor coil is perpendicular to the spin axis of the iron sphere (which the coil spins with, since it’s directly attached), and the direction of the length of the stator coil is parallel to the spin axis of the iron sphere. Commented Apr 20, 2023 at 20:55

• Getting an exact frequency and amplitude aren’t a concern: I thought of a 5, 6, 6.3 or even 3 V transformer, relying on some sort of series resistance to not overload the stator winding. Commented Apr 20, 2023 at 21:13