Build an Electric Motor the Easy Way

Polish version is here

Simplified but Functional Model

There are many types of electric motors, and they can be classified according to various criteria. One of these is the type of current supplied to them. We can distinguish between direct current (DC) motors and alternating current (AC) motors.

One of the first DC electric motors was Faraday's disk, which, like many motors, was a reversible machine. When supplied with mechanical energy, it produced electrical energy.

Today, we will build one of the simplest possible but functional models of a DC motor.

Materials

The materials needed to make this toy can be found in any household. We need:

A small amount of enameled wire, with a diameter of 0.3-0.6 mm (0.012-0.024 in.)
1.5V battery (AA battery)
A small magnet
Tools: scissors, combination pliers

A soldering iron will also be useful.

Let’s Get to Work

Wrap the enameled wire around the battery a few times, creating a small loop that will serve as the motor’s coil. Then secure the coil by wrapping the wire ends around it so that it doesn’t unwind.

Source: http://sci-toys.com/scitoys/scitoys/electro/whole_coil.jpg, accessed: 05/13/2013

To prepare the rotor, remove the insulating enamel from the ends of the wire, which will act as the axle. Additionally, one end will also serve as a primitive commutator. Therefore, while one end must be stripped of enamel around its entire circumference, the other end should be stripped only on one side—either from the top or bottom:

The easiest way to do this is to lay the straightened end of the wire on a flat surface, such as a tabletop, and then scrape off the enamel from the top using a razor blade. Remember that the other end must be stripped of enamel around its entire circumference!

Finally, straighten the axle so that the rotor is as balanced as possible.

Next, create two small loops (bearings) that will allow the rotor to spin. The diameter of the loops should be approximately 3 mm (about 0.12 inches) (it’s best to use a nail to shape them).

Solder the wire pieces with the bearings onto the battery. Then attach a small magnet to the battery so that one of its poles faces upward. The whole setup should look something like this:

Now, if you place the rotor on the bearings, it should spin rapidly around its axis. Sometimes a slight push is needed to start the rotation. You can see this simple electric motor in action in the video below:

You can also build a more durable version of this physics toy. I used a larger magnet from an old speaker, which I attached to a universal printed circuit board using small pieces of wire. I also soldered more rigid supports to the board. A 4.5V flat battery is placed under the board, with wires running underneath to supply voltage to the supports. The jumper visible on the right side acts as a switch. The construction looks as follows:

Kliknij, aby powiększyć

Kliknij aby powiększyć

The operation of this model is also shown in the video:

How and Why Does It Work?

The trick lies in using the electrodynamic force. This force acts on any conductor through which an electric current flows when placed in a magnetic field. Its action is described by the left-hand rule.

When current flows through the coil, it experiences an electrodynamic force because it is in the magnetic field created by the permanent magnet. This force causes the coil to rotate until the current flow is interrupted. This happens because one end of the axle, which supplies the current, is stripped of enamel only on half of its circumference. Although the force no longer acts, the coil continues the second half of its rotation due to inertia. This cycle repeats when the axle rotates back to the stripped side, closing the circuit again.

The electric motor presented here is a simple yet impressive physics toy. Since it has no practical applications, playing with it is pure fun.

Enjoy and have fun experimenting! :)

Weird Science