Making Magnet Out of Copper Wire and Battery

[bostonman]

Is there a difference between using "thin" copper wire for wrapping it around a nail and attaching a battery versus standard wire?

I've wrapped a standard (solid) wire around a nail and attached a 9V. All I get is the 9V dropping to 0v. Although, now that I think about it, maybe the nail is zinc plated - if that matters.

[TimFox]

"Magnet" wire, with thin enamel-like insulation, allows more turns in a given volume than "hook-up" wire with thicker plastic insulation.  "Solid wire":  is it insulated?  If not, you will get shorts between turns and extremely low resistance.  It sounds like your coil has very low resistance and is just shorting out the 9 V battery.  The zinc plating should not matter for a DC electromagnet.  How long a piece of wire and what gauge did you use, and did you look up the expected resistance in a wire table (easily found online)?  What current do you expect out of your 9 V battery?

[bostonman]

Most things I’ve seen use enough wire to wrap around a 3” nail or screw. I’ve never built one and this is why I’m curious and thought a relay would use many more turns than what I’ve seen.

I agree, the wire isn’t long enough, but most things I’ve seen don’t seem to use many turns.

[ArthurDent]

A 9 volt battery typically has a load that draws 10 ma and if you're not concerned about battery life, 100 ma. You're not too clear about what wire you're using and probably used a few turns of wire that has almost zero ohms resistance which will be a dead short across the battery as mentioned above.

If you want to make an electromagnet that would draw 100 ma from a 9 volt battery it would take about 1000 feet of #30 magnet wire to meet those specs. If you check a copper wire table you can find the resistance per 1000 feet of all wire sizes to help calculate the wire needed. If you look at the photo below of a relay, that is basically a electromagnet use to switch circuits, you can see the very large number of turns of very tiny magnet wire used to create the magnet coil.

Consider that as the number of turns doubles and the current used by the coil halves, the strength of the magnet remains about the same. Try using about 100-200 turns of small wire or replace the 9 volt battery with a 1.5 volt D cell to be able to pump more current at a lower voltage through the coil. You still should be careful not to cause heating of the wire by having too low a resistance.

[tkamiya]

You CAN use thin insulated wire like wire-wrap wire, make 100 turns around a big nail, and it does work - I've done it.  it's not the copper or wire that produces magnetism, it's the current that flows through it.  Though amount of magnetism such can create is just enough to move a compass needle, or a small amount of fine iron dust.  Speaking of compass, a wire, a single wire, no turns - is enough to make compass needle move.   Yes, connecting to 9V battery will make it awfully hot....

Use of many turns of magnet wire is more practical for making a useful magnet.

By the way....  if you use THICK wire and make 5 turns, then apply 100A to it, you can create a HUGE flux.  Put a lot more, and it's enough to crush cans.

[bostonman]

I never tinkered with making my own magnetic, and didn't give this much thought. I knew a length of wire that could only make it around a nail 15 or 20 times wasn't long enough to avoid shorting the battery, but thought I'd try it anyway.

The wire I'm using is probably 24AWG and regular insulation.

The parts I didn't give much thought to was using a 9V battery instead of 1.5. I figured the more voltage, the greater magnetic field.

In any case, I don't have magnetic wire, but at least I know where I went wrong.

[tkamiya]

In old days, there were LOTS of kits for "Morse Code trainer" which used the type of construction you mention.  Even with 24 wire gauge, there isn't enough resistance, so battery will get awfully hot.  Please don't use Lithium type!  Insulation will probably melt and before that, it will become too hot to handle.

200 turns or more can probably pick up a small paper clip with 1.5 volts.

Yes, more voltage = more magnetic flux, but more current = more heat, too.

[james_s]

More voltage doesn't get you more flux directly, it gets you more current which gets you more flux, IF your source can supply the current. A 9V battery has a rather high source impedance, they're not meant to deliver a lot of current, it's likely that a 1.5V D cell will push a LOT more current through a coil with so few turns and result in a much stronger magnet.

I made electromagnets like this when I was a kid. A couple dozen turns connected to a 1.5V battery will pick up a few tacks or iron filings. To make a reasonably efficient magnet you'll want a lot more turns of thinner wire though.