Making an electromagnet...

You're better off with a closed magnetic path if you can find something magnetic with the correct shape, ie. U shaped with flag parallel ends, the coil wound round the middle, and picking up something that closes the gap like an iron plate or bar. A wide cross section and not-too-long arrangement will work better.

Since you're not interested in the finer points of magnetic behaviour, you may find ordinary iron or steel works better than ferrite.

For something around the size of your fist, maybe a couple of hundred turns of #20 or #22 enamelled wire, a 12 volt DC supply and a bit of resistance to keep the current from getting too high and burning out your coil. #20 is good for a couple of amps IIRC. Google will give you resistance / metre for various wire sizes.

"DD"

** Err - what shape is the core.

Not ring shaped I hope.

** Forget ferrite - it has a low magnetic filed strength.

Try using a 1/2 inch dia, 6 inch long, mild steel bolt with about 250 turns on it.

Even a 1.5 volt D cell should do the trick with that.

...... Phil

Mild steel will work much better than ferrite but magnetically soft iron or silicon steel would work better: if you could salvage the E cores from a plugpack transformer and run power to the low voltage secondary you should have something fairly usable to begin with.

Try about a hundred turns of wire around a roofing nail & power it with a 'D' size battery. That's how the demo was usually done when I was a schoolkid.

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