When I was a kid, I wound a nail with enamel-coated wire, starting from the head of the nail, then when I reached the tip, I would wind towards the head again (still in the same direction of rotation though).
Was this a mistake?
Would I have had a stronger electromagnet if I had a straight run of wire back to the head of the nail, then proceeded with winding?
In short, no.
It's the direction of rotation that matters, going straight back to the top and doing a second layer waould have wasted wire, and also made the turns looser, two bad things.
Ok thanks guys!
Michael
No. It's the number of turns all going in the same direction that make it work.
As a thought experiment, consider replacing 100 turns of enameled wire with 100 turns of really thin insulated foil -- your electromagnet would behave pretty much the same at DC, although I wouldn't answer for any inter-winding capacitance issues.
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