I do this more as an activity than anything else. I end up trying to cover electricity and magnetism in about two weeks, not anywhere near what is needed. I try to make the material relevant because it’s above most of the students in my conceptual physics classes. This is one of those activities where they amaze themselves.
I got the plans for an electric motor design from the book “Teaching Physics with Toys” by Taylor, Poth, & Portman. This book is really geared towards K-9, but I figure that if I find the activity cool, then why wouldn’t an 11th or 12th grader. I have the 1995 edition, they have a new edition that I haven’t seen. I don’t even know if this activity is in the new edition.
You can find similar activities on the web. (Build It: Electric Motor), but I like the design in the book better. Basically, you need a D cell, a doughnut magnet (available at Radio Shack), some bare heavy wire, like 14 or 16 gauge, some transformer or magnet wire (22-28 gauge), and a piece of sandpaper.
You take an arms length of the transformer wire, leave about 2 inches and wrap the rest around a dowel 5/8″ dowel or a white board marker, then leave another 2 inches at the other side.
As you may be able to see from the picture to the left, the leads are wrapped around the coil to tie it all together. It is important to try to balance the coil so that the leads are along the centerline of the loop. Next, sand the ends of the magnet wire so that the red coating is gone and you can see bare copper.
The magnet goes on top of the battery and will hold the top lead in place. You bring the negative voltage up with a bare copper wire, we use tape to hold the negative lead in place. Make a loop at the top of each with a pair of plyers. Try to make the loops on top at the same height so the motor doesn’t slide sideways.
To start the motor, just put it all together. You usually have to remove the positive lead to fit the winding coil into the loops. Put the leads back on and pop the magnet in place. If its really well made, the motor will begin spinning on its own. That rarely happens. Just give it a light spin. You will need to play with the leads to get them centered, but then when you get it right, it can run for hours.
Can I expand on your post?
I want to add something about electric motors:
An electric motor uses electrical energy to produce mechanical energy. The reverse process, that of using mechanical energy to produce electrical energy, is accomplished by a generator or dynamo. Traction motors used on locomotives often perform both tasks if the locomotive is equipped with dynamic brakes. Electric motors are found in household appliances such as fans, refrigerators, washing machines, pool pumps, floor vacuums, and fan-forced ovens.
The classic division of electric motors has been that of DC types vs AC types. This is more a de facto convention, rather than a rigid distinction. For example, many classic DC motors run happily on AC power.
The ongoing trend toward electronic control further muddles the distinction, as modern drivers have moved the commutator out of the motor shell. For this new breed of motor, driver circuits are relied upon to generate sinusoidal AC drive currents, or some approximation of. The two best examples are: the brushless DC motor, and the stepping motor, both being polyphase AC motors requiring external electronic control.
There is a clearer distinction between a synchronous motor and asynchronous types. In the synchronous types, the rotor rotates in synchrony with the oscillating field or current (eg. permanent magnet motors). In contrast, an asynchronous motor is designed to slip; the most ubiquitous example being the common AC induction motor which must slip in order to generate torque.
Comment by Dave — June 2, 2008 @ 9:35 pm |
I did this when I was student teaching with 8th graders. The looks of excitement on their faces when their motor spun on it’s own was priceless.
Our plan was a little different and easier in a middle school environment (i.e. less science supplies on hand, like thick copper wire) We used an upside down disposable cup as the base. Two paper clips for the armatures/leads and mounted the battery sideways on the cup.
Good fun.
Comment by Bryan — September 22, 2008 @ 2:00 am |
Bryan, I am looking for the instructions for the motor you describe. Could you post it or email it to me? D.
Comment by dana — March 19, 2009 @ 6:31 pm |
I’m having some difficulty with this project, as my teacher requires the 22 gauge wire to move something as it spins.
Do you (or anyone else for that matter) have any suggestions on a way to increase the power, or ideas on what this would work to move?
Comment by Mayde — December 8, 2008 @ 11:07 pm |