DR. GADGET'S SCIENCE MACHINE
Make your own electric motor
By Joe Laszlo
A fun look at science working in the world around you, plus a cool gadget or experiment to test it out
Aloha! Let's make a simple electric motor. Get a battery, two paper clips, a small magnet and a piece of thin insulated wire, such as telephone wire, about 2 feet long. You will need some pliers to bend the paper clips as well as some masking tape. Start by making a coil of the wire. Wrap it around something that is about an inch in diameter and use 8 to 10 turns (Figure 1).
Secure the coil so it doesn't come apart by wrapping each of the free ends of the wire around the coil at opposite sides of it (Figure 2.) Have about an inch of the free ends sticking out from the coil, in line with each other at about the half-way point of the coil on both sides of it. Scrape off the insulation from both ends that are sticking out (Figure 3). The coil of wire is the armature.
Bend the paper clips into brackets (Figure 4). They will be taped to each end of the battery and will support the armature and also carry electricity from the battery to the coil. You should have a loop in one of the paper clips that fits over the "button" on the top of the positive side of the battery (Figure 5).
Tape the brackets to each end of the battery. The point where the straight ends sticking out of the armature sit and rotate must be level, or your motor won't work well (Figure 6). These ends sticking out act as commutators and the paper clip brackets act as brushes, besides giving the armature support.
Put the armature onto the support brackets and spin it a couple of times to see if it is balanced and turns level. If not, adjust it. When it is balanced, place the magnet onto the battery. The magnetism will cause it to attach to the battery. The motor should start going almost immediately when the magnet is in place. A note of caution, the armature will get warm, or even hot depending on the voltage of the battery, so be careful.
Why does it work? The armature becomes an electromagnet and, depending on the way you wrapped the coil, it is either attracted or repelled by the magnet. The contact between the commutators and the brushes isn't that great, but that's good. It causes a "make and break" in the current flow. The current starts and stops. This allows the polarity of the armature to change as it rotates. The magnet is always North on one side and South on the other. The changing of the poles of the armature causes the rotation.
You might try making it with fewer turns in the armature, or more turns, or the same coil but double up on the magnets. Change one thing at a time and observe the results. It might be interesting to see if this works with an AAA battery, or a calculator battery. Maybe one of you "Gadgeteers" out there will do it. Let me know what you discover. A hui hou!
Do you have a question or suggestion for Dr. Gadget? Mail your letter with your name, age, school and telephone number, to: Dr. Gadget, c/o The Honolulu Advertiser, P.O. Box 3110, Honolulu, HI 96802, or fax 535-8170. Send e-mail to ohana@honoluluadvertiser.com only if you're 13 or older; otherwise, have your parents do it for you. "Dr. Gadget's Science Machine" is written by Joe Laszlo , a retired science teacher.
