# Help with electromagnet design

Hi everybody,

I just had 100m of copper winding wire arrive in the mail so I can build an electromagnet.

I'm aiming to pull a 5kg weight along, which is already floating on a separate magnetic field so all friction is removed except air resistance.

What I want to do is put an electomagnet in front of this 5kg box, to pull it along on a cushion of air - similar to the Japanese maglev trains.

(except mine is awesome).

So here's the thing.

I'm trying to make the smallest electromagnet I can out of this wire.

I wound it all around a little a plastic air core with a diameter of 6mm. There's 100 turns of wire, wire is 0.2mm, copper, 36SWG.

Hooked up a 9V battery.

Nothing - no force.

I know... you are going to say the number of turns is too low.

But before I spend the next 2 hours going mad winding up this tiny little thing with 100,000 turns, I wonder if someone could help me with a few specs for the design.

Best guess at what size radius core to use (air core), how many turns, and voltage to apply.

I'm stuck with standard battery voltages - multiples of 1.5v, or 9V.

Use an iron core , Up the current .

Use an iron core , Up the current .

I did try with an iron core - no effect.

I'm not sure how to up the current when the resistance is fixed (the length of wire) and the voltage is fixed within those ranges.

You should be able to attract bits of iron with the magnet you have described, air core or iron core. Something is wrong. You did complete the circuit, right? One pole of the battery on one end of the wire, the other pole on the other end? Its possible that you are trying to draw too much current out of the battery, and are dropping its voltage when connected. You really need to be careful in this design. I think SWG36 will only handle about 70 milliamps of current, so you need to make sure that the resistance that your 9v battery sees is about 127 ohms. If the wire does not give you that, then you should drop your voltage until V=IR where I=0.07 amps (70 milliamps) and R is the resistance of your coil.

What I want to do is put an electomagnet in front of this 5kg box, to pull it along on a cushion of air - similar to the Japanese maglev trains.

It isn't on a cusion of air. Air has nothing to do with it.
I know... you are going to say the number of turns is too low.

Sounds like more than enough for a basic magnet.
I'm stuck with standard battery voltages - multiples of 1.5v, or 9V.

Put in an iron core and attach as many batteries as possible. If it doesn't attract, I'd say your batteries are cream-crackered.

However, you're not using AA, AAA and 9V (small rectangle) batteries are you? They can't deliver anywhere near enough current. 9V batteries are rated at around 0.2A. Connecting about 10 of them in parallel and you'll get enough to give a good field - although I wouldn't recommend this as it may be dangerous.

It isn't on a cusion of air. Air has nothing to do with it.

It's a metaphor. As in poetry. Thankyou for pointing out the obvious.

Thanks everyone. I got a tiny bit of pull from the electromagnet now.

It's a metaphor. As in poetry. Thankyou for pointing out the obvious.

Well it reads like a statement, and as such is wrong.