I find some material on this subject but nothing seems to directly answer my questions.
Is there a formula that can be used to determine how much current is needed for electromagnets? Or what a known setup will draw? What affects the current draw, wire size, turns, etc?
What affects the strength of the magnet? I know number of turns has a lot to do with it but what about voltage or current?
For a DC electromagnet:
Current = applied coil voltage/wire resistance.
Wire resistance is proportional to wire length and inversely proportional to wire diameter.
Yes,This is true, But you must keep in mind that only the current is directly proportional the the magnetic field and not the voltage it takes to setup the current due to the resistance of the wire.
So what limits the current that the coil draws? Or does it draw what is available? I'm looking to build a fairly strong magnet with as little current draw as possible.
As misterT said, for a given magnetic field with minimum current, you need to use small wire with many turns. Generally you use as small a wire (enameled wire) as can be easily wound without breaking.
Thank you everyone, this is the type of info I need.
When winding the coil and you reach the end of the core, do you wind in the opposite direction for the next layer or start back at the original location and keep the layers ending on the same side?
You wind in the opposite direction (meaning left to right then right to left). You must have all layers in the same rotary direction (e.g. clockwise, as seen from one end of the core).