[phpBB Debug] PHP Warning: in file [ROOT]/includes/functions.php on line 4464: Undefined array key "Cookie"
Science Buddies: "Ask an Expert" • FAQ for Strength of an Electromagnet Project
Page 1 of 1

### FAQ for Strength of an Electromagnet Project

Posted: Tue Jun 26, 2012 12:08 pm
The following FAQ contains frequently asked questions and answers about the Strength of an Electromagnet project. If you are having trouble with the procedure, you may find assistance in the answers below.

Q: I am having trouble keeping track of how many turns are in my coil. Do you have any suggestions for tracking that better?
A: If keeping track of how many turns of the magnet wire you have made around the iron core becomes difficult, here are two suggestions. First, draw a line straight down the iron core with a permanent marker. Count one turn each time you pass the marker line. Second, each time you add ten turns to your coil, draw a short line on the core next to the wire, and write down how many turns you have so far. If you get distracted, you can unwind to the nearest multiple of ten, instead of unwinding all the way back to the beginning. It is useful to have a helper track how many turns you have made.

Second, if you know the gauge of your magnet wire, you can look up the diameter of the wire in a table, like this one: http://en.wikipedia.org/w/index.php?tit ... =495948718. Once you know the diameter of the wire, you can calculate how much of the iron core should be covered by a certain number of coils. For example, the wire in the Science Buddies kit is 30 gauge wire and has a 0.01 inch diameter. That means that 100 turns of that wire cover 1 inch of the iron core (0.01 inches x 100 = 1 inch), if the turns are right next to each other and do not overlap. So, if you wrap your coil very neatly, you can estimate how many turns are in your coil by measuring how much of the iron core is covered by the coil. This can be a helpful "reality check," especially if you completely lose count of how many turns you have made in a coil. Note that this method does not work if your coil has more than one layer of wire or if there are spaces between turns.

Q: I am having a hard time keeping my coil neat. Any ideas for keeping my turns tight and lined up nicely?

A: We suggest starting your coil as close to the top of the bolt as possible so that you have most of your coil on the non-threaded part of the bolt. The 50- and 100-turn coils should fit completely on the non-threaded section of the bolt. For larger coils, you have a couple of options. First, you can ignore the threads and keep on wrapping, even though it will be harder to keep the turns lined up because the wire will tend to lie in the threads of the bolt. Second, when you reach the threads, you can start wrapping the coil in the other direction, away from the threads and on top of the first set of turns, creating a second layer to your coil. Either option gives good results.

Q: The magnet wire breaks when I try stripping it with sandpaper. How can I stop this?
A: Try using less pressure. You do not need to squeeze the sandpaper sandwich very tightly in order to remove the enamel insulation that coats the magnet wire. Try practicing on a separate piece of wire to get a feel for how much pressure to apply with the sandpaper. If you did break the magnet wire "tail" of your coil while stripping it, do not worry. You can strip the insulation off the remaining part of the wire tail. You do not need to start over or make a whole new coil, as long as you have enough stripped wire for the alligator clip to hold.

Q: How do I know when the wire is stripped?
A: The wire is stripped when the reddish color of the enamel insulation is gone, revealing bright, shiny, golden-colored copper. The wire will also look a little bit thinner.

Q: My electromagnet is not working. How can I make it work?
A: The electromagnet might not be working for a number of reasons, but most of them boil down to an incomplete circuit. In other words, the electromagnet will not work if something is preventing electric current from flowing from the battery through the wire.

First, check that the electromagnet is correctly connected to the battery. Make sure the alligator clips are connected to both the battery and the wire. One end of each clip lead should be connected to one of the terminals of the battery (one lead to each terminal), and the other end of each lead should be clipped to the stripped part of the magnet wire (one lead to each end of the wire). See Figure 1. If the clip leads are connected correctly to the coil and battery, but the electromagnet is still not working, then the problem may be that the magnet wire is not completely stripped. Look at the answer to question 5 and determine if your wire is well stripped. If not, try re-sanding the ends of the magnet wire until all of the reddish insulation is gone, then reconnect and retest the electromagnet. If the electromagnet is still not working, check to make sure the alligator clips are well clamped to the stripped part of the magnet wire tails. They should not be clipped to the insulated part of the magnet wire, as insulation prevents electric current from flowing. If the electromagnet still does not work, then the battery may be dead. Try replacing the battery with a new one.

Figure 1. Connect the electromagnet coil to the battery using two alligator clips. Clip one lead of each alligator clip to each of the battery terminals. Then clamp the second lead of each alligator clip to the stripped part of the wire tails, one lead to each tail, as shown here.

Q: The wire tails of the electromagnet keep falling out of the alligator clips. What can I do about this?
A: Try putting the wire farther back in the clips, closer to the hinge where you squeeze to open the clip. You can also try stripping the insulation off a longer section of the magnet wire tail and folding over the end of the tail to make it thicker. The alligator clips will hold this thicker section of wire more easily. If you have enough stripped wire, you can also wrap the wire around the tips of the alligator clips.

Q: My finished coils are coming uncoiled because the tape holding the end in place is falling off. Do you have any suggestions for preventing that?
A: Try wrapping a piece of masking tape all the way around the bolt, covering the last part of the coil. As you use the electromagnet, the heat that builds up in the magnet can make the tape brittle, so it is a good idea to apply new tape instead of reusing old tape.

Q: I see sparks when I connect the alligator clips to the coil. Is this something to worry about?
A: No, small sparks are not something to worry about. It is completely normal to see a few small sparks as you connect the alligator clips and complete the circuit.

Q: My electromagnet gets warm and starts to smell. Is this something to worry about?
A: The current running through the circuit will heat up the wire. Whenever you detect a smell, or can feel the electromagnet getting hot, disconnect the electromagnet from the battery. You can reconnect the electromagnet after it cools down.

If you have other questions about the procedure or need assistance troubleshooting your Strength of an Electromagnet project, please post your question in the forum for this kit at Ask an Expert: https://www.sciencebuddies.org/science- ... m.php?f=68. Our team of volunteer Experts is available to assist. We attempt to reply to questions within 24 hours. Please note that you will need a free Ask an Expert account in order to post questions.