In this lesson we'll create two simple motors and measure their relative performance. We'll also see how a few different resistors change the performace. To begin, we need to create the rotors for our motor. For this simple case, the rotor is a coil of wire. Follow along with the pictures to create two rotors.

Using the 1 inch plastic spacer in the kit, start a coil of wire. For the first rotor, we'll wrap the wire around the spacer 10 times. Make sure to leave some wire uncoiled at both ends.

Take one end of the wire that's uncoiled and wrap it around the coil to make a little arm. This will help hold the coil together, and it will also support the rotor in the body of the motor, or stator.

On the opposite side of the first arm, wrap the other uncoiled end of wire the same way. You'll now have two arms, directly opposite from each other.

Set that coil aside for now and create another. This time wrap the wire around the spacer 15 times. Then create two arms by wrapping the ends around the coil on opposite sides.

The wire we're using for our rotors is coated with enamel that doesn't conduct electricity. To make our motor work, we'll need to strip all of the enamel off of one end, and half of it off the other. Follow along with the pictures below to strip the ends of your rotors.

The easiest way to strip the enamel is with a razor knife. Lay one arm of the rotor flat on the table and scrape the knife across it to remove the enamel. You don't need to press down, just place the blade on the wire and scrape sideways. Then, rotate the arm a little and repeat until it's bright copper all the way around. Make sure you get all the enamel off.

On the other arm, we only want to remove one side of the enamel. Look carefully at the picture. Remove enamel the same way you did with the last arm, but only half of it. On the half you stripped, make sure there aren't any lingering pieces of enamel.

Repeat this process for the arms of your other rotor. Remember, one arm will be stripped completely. The other arm will have half the enamel removed.

To get the best performance from your motor, the rotor will need to be balanced. Part of this is ensuring that the arms are directly opposite of each other. To test the balance of the rotor you can suspend it by the arms from your fingers and see how it rotates. (It's much easier to do before you insert it into the rest of the motor.)

If one side is much heavier than the other try to adjust it by slightly bending the arms or sliding them around the coil. It can also help to very slightly squish the circle into more of an oval with the arms at the long ends. The balance doesn't have to be perfect, but the better it is, the faster your motor will turn.

After you've balanced the rotor with 10 windings, place a small plastic spacer on each arm if there's room, and insert it into the motor body. You can turn the metal arms of the stator out slightly and then turn them back in with the rotor in place. Make sure that the motor doesn't scrape the magnet when it rotates, and that it it rotates freely. Now we're ready to run some tests!

Now we'll use an infrared sensor to measure how many revolutions your motor makes in a minute. First connect one alligator clip from the red and black wires to the corresponding colors on the battery holder. Next, connect the other clip of the black wire to one of the bolts on the stator. Connect the other end of the red wire to a 4.7 ohm resistor. Then, connect a yellow alligator clip wire to the other end of the resistor. Finally, connect the other end of the yellow wire to the other bolt on the stator.

Don't worry if your motor doesn't start spinning right away. Almost all of them need a little push. Give it a small push to start spinning in one direction. If it seems to resist that direction, try spinning it the opposite way. If you notice a balance problem and need to correct it, disconnect the power from one side first and reconnect it when you've got the rotor back in place. If left spinning for a long time, the rotor could get a little warm, so be careful.

After the motor has stabilized, note the RPM and try again with a 3 ohm resistor. Then with a 1 ohm resistor. What do you notice about the RPM in relation to the resistor? You may need to balance the rotor again after it spins for a while. If so, disconnect the power first.

Now we'll repeat the same process using the rotor with 15 windings. Start with the 4.7 ohm resistor again. Then move to the 3, and finally, 1 ohm resistors.

What difference do you notice between this rotor and the rotor with 10 windings? Do the resistors have different effects on this rotor than they did on the other? Given the results of the experiment, what can you guess about the relationship between the number of windings and the RPM of the motor?