Can I safely build an electromagnet?

Alright, I have a AA battery, a whole bunch of wire and some nails. My plan is to wrap the wire around the nail, and connect the two ends of the wire to the two ends of the battery.

Bottom line: Will the battery explode? I’m afraid that just running a wire from one end of the battery to the other will make it explode, even if the wire goes around a nail along the way.

Depends on how long the wire is. The longer the wire, the more resistance it has, and the less current it will draw.

It also depends on the cell chemistry and internal resistance. Some cells will rupture or explode if shorted, some will merely get hot.

Using a AA battery? No, the battery will not explode. I used to build electromagnets all the time using batteries larger than AA. So have at it, you will have no problems.

I did an electromagnet as a fourth grade science project, using a big lantern battery. No explosions. Go for it.

Of course, with a AA battery, you’re not going to get a particularly mighty electromagnet, nor a particularly long-lasting one.

I don’t think there’s much risk if you’re using a primary cell (e.g. Carbon Zinc or Alkaline). At worst the cell might get a little warm. But be careful if you’re using a NiCad or lead acid battery; shorting these types out could cause them to catch on fire.

A nail electromagnet? C’mon, to get any kind of decent effect, you need to wrap the wire around a cannon: To wit, from the March, 1917 QST:

If you are using a NiCd battery and a short piece of wire then you may burn up the wire but the batt. won’t explode. (Alk’s have too much internal resistance to burn up the wire)

I based my response on: a) What I’ve heard, and b) claims such as this:

“Consequently, some cells are inherently able to produce high currents. Others can only product weak currents. For example, the currents produced by lead-acid batteries and nickel-cadmium cells are so high, such batteries can melt metals and start fires when shorted out. Put an unpackaged NiCad battery in your pocket, and it may short out against your keys and change. The high current and heat from the short circuit could start a fire. Consequently these high-current cells often wear warning labels.”

But to be honest, I’ve never tried it. So do an experiment for the good of us all: Charge a NiCd, short it out, then report back. If you feel extra-adventuresome, use a D-size NiCd with 10 A capability.

Crafter_Man I didn’t read you responce before I posted (I just posted what I knew from experence to the OP) but NiCd can produce dangerous amounts of current. IIRC a D cell radioshack high capacity NiCd will cause a standard thin (forgot the gauge) wire to heat up and glow red and melt. I think it will blow a fuse in 10 A DC multimeter if shorted (alks will produce something like 2A if shorted across the meter).

I think the fire is from heat of the wire (or change in your pocket) not from the battery - but I guess it’s possible to.

I agree NiCds are probably designed to not melt or catch on fire if shorted, and the bigger risk is the load. But who knows? Maybe I’ll try it and see what happens…

Recursion, that would make a very poor electromagnet and the battery would last no time. If you tell us what you are tryimg to accomplish I may be able to give you better ideas.

Thanks to everyone for your responses to my question. I have not gotten the chance to try out the electromagnet because I’ve been pretty busy. (Or maybe I’m just afraid the battery will explode.)

sailor: Just because you were curious, I will tell you exactly what I’m up to. I decided to build a “computer” (really, just a simple calculator). I was going to build a whole bunch of electromagnets, and use them to make relays* to make the really, really slow “computer”. I know enough about Boolean logic gates to actually do it if I had enough time. Unfortunately, I don’t know enough about actual electric circuits, so the project hasn’t really gotten off the ground. I really didn’t think I’d go much farther than making a 1-bit full adder, anyway.

I had planned to introduce myself to this idea by making a simple electromagnet with a AA battery to get myself started. Obviously, I wasn’t planning to use AA batteries in the final product.

*Why relays? Because I wanted the “adding machine” to make mechanical noises whenever it ran.