Science Buddies: "Ask an Expert"

We are encountering an issue with our experiment making an electromagnet (see question at the bottom).

Items:
3.5 inch nail
22 AWG enamel coated copper wire
6v dry cell battery.

Project is testing whether adding multiple individual coils of wire around a nail will increase the electromagnet power.
We know that if you take a single wire and wrap it around the nail 30, 60, or 90 times the power will increase as you increase the wraps around the nail. However what if you wrap a nail with wire 90 times. Then take a new piece of wire wrap the nail in the same direction directly on top of the other wire again 90 times and repeat it a 3rd time. So you have a total of 3 individual wires wrapped around the nail?

Test:
1.) Take the first wire and attach each end to the battery (+ and -), see how many paper clips it will pick up.
2.) Attach the first and the 2nd wire coils and attach each end to the battery (+ and -), see how many paper clips it will pick up.
3.) Finally attach the first, second, and third wire coils and attach each end to the battery (+ and -), see how many paper clips it will pick up.

Results:
1.) 1 wire - picked up 26 paperclips
2.) 2 wires - only picked up 6 paperclips
3.) 3 wires - only picked up 11 paperclips

Question (confusion):
The assumption was that like wrapping a nail with a copper wire 30,60,90 times would increase the power of the electromagnet, so would adding separate individual wires (as described above). However we found that was not the case. Can someone explain why this would not work or what we are doing wrong?

Thank you in advance for your help and guidance!

The current has to always flow in the same direction through any of the coils. Looking from one end of the nail it has to go either clockwise or counterclockwise. I agree that powering more coils should increase the magnet's strength and I'm wondering if you may have connected the additional coils backwards.

When yo wound the first coil, you had one end of the wire sticking out - we'll call that end A. You wrapped the wire around multiple times and and up with end B. On the second coil you started with one end (call that C), wrapped the same direction as the first coil and ended up with end D. When you connect the battery to the two coils, one battery terminal goes to A and C and the other to B and D. I'm wondering if you connected A and D to one terminal and B and C to the other. Is that possible?

Howard

Hi Howard,
I appreciate the response. To answer your question I made sure that I connected the wires correctly to the battery. Per your explanation wire ends A and C to positive and B and D to negative.

I'm finding all sorts of articles on the internet about making electromagnets that way and no one is suggesting they get the same results you are. I'm going to read some more but maybe someone else here has a suggestion. It's especially odd that two coils is weaker than one, but three is stronger than two.

I'm sure there's a logical explanation here somewhere.

Howard

Thanks Howard... yes this is very frustrating. I initially thought we were doing something wrong or causing some issue with sending current through two different wires from the same battery or some other scientific reason as to why this would not work.

The other day we wrapped a new nail with new wire, etc to see if the results were any different or if one of the wires had bad enamel coating thus causing a short or something. Unfortunately the results were the same.

Last night I wrapped another nail but after I wrapping the first wire I put down a layer of electrical tape to ensure the next wire sat on top of the first rather than working its way in-between the first wire,etc. Again, that didn't work. So I am completely perplexed as to why we get the best results with only the first wire and when connecting the other wires to the battery decreases the magnetic power.

Again, I appreciate your help in troubleshooting this issue. Hopefully one of us or someone else on this will have or find the answer.

What *would* be true with the coils connected in parallel but powered off of one battery is that the could may not power evenly. Even if you have the same amount of wire, the electrical and magnetic properties of a coil will appear as resistance and affect the amount of current flowing through each. No matter what though, adding more coils should result in a lot more current being drawn off the battery and hence a stronger field.

One thing that occurs to me is that a 6V lantern-type battery can't put a huge amount of current. It's possible that you're trying to pull too much current from the battery and limiting the overall amount of power it can put out.

If you have extra batteries, what happens if you power each coil from a separate battery? Keep the polarities correct as you did in your other test - maybe giving the coils the power they want without starving them would give you the results you expect. Or put three batteries in parallel first and then try the experiment as you did it.

Do you have access to a multimeter? Measuring the current draw from the battery might tell you something revealing.

Howard

Sorry for the late response. Volt meter definitely reflected that attaching additional coils to the same 6V battery reduced the amount of total voltage, so it makes sense. We ran out of time to try a higher voltage battery or try multiple batteries. We went with the results and modified his conclusion and final thoughts based in the results and what we expected.

Thanks for your help.