Coffee Cup Motor

FIELD: Physical Science DURATION: 1.5 hr.
OBJECTIVE: Students will know the basics of how electric motors work.
METHOD: Students construct a simple electric motor using a battery and household items.
KEY VOCABULARY: Motor, magnetic field, current, electricity. GROUP SIZE: Any


Electric motors are found in a huge number of common appliances: fans, hairdryers, toy cars, weed whippers.

Electric motors all work on the same principle. This basic principle is that an wires carrying electrical current feel a force in a magnetic field. There are two key components to a motor: a permanent magnet and an electrical current. Permanent magnets are composed of particular materials, such as iron, which always emit a magnetic field around them because of small electrical currents always flowing inside. When a wire or coil of wires carrying a current is in this permanent magnet's field, it is pushed in a particular direction.

When a motor is plugged in, current flows in a coil of wire (we use a coil because the amount of force is proportional to the amount of current and a coil adds extra current with every loop). Because of the physical arrangement of the coil, the force it feels will start to spin it. As the coil comes around again to this original position in the magnetic field, it gets another 'kick' and spins again, and so on. When you get your coffee cup motor working, this will make perfect sense!

In this experiment you will arrange a coil of electric current-carrying wire and a permanent (bar) magnet to create a simple electrical motor.

MATERIALS (per group):

Wire with painted insulation covering - 1 meter (40 in.)
NOTE: You need light wire with a very light painted-on coating of insulation that can be scraped half-bare. Rubber insulated wire will not work.
Stryofoam cup
1 flashlight battery (1.5 volts D Cell)
2 paper clips
1 bar magnet - 1 in diameter or so.
Masking tape
Sandpaper (rough)


1. Wrap the wire around the D cell battery several times to make a tight coil.
2. Leave 3-4 centimeters free at each end.
3. Loop the free ends around the coil to hold it together leaving an inch or so sticking out.
4. Remove 1-2 centimeters of the insulation from only half of the circumference of the wire sticking out. See fig.1.
5. Place the styrofoam cup upside down on the table and position the battery on top of it.
6. Cut the bottom of the cup so the battery fits snugly inside. The coffee cup serves as a stand for the round battery.
7. Bend the paper clips as shown in fig.2 and tape one to each of the battery's terminals (you can also use a rubber band to help keep the paper clips up against the battery).
8. Tape the bar magnet to the top of the battery, lying flat.
9. Carefully lay the coil across the paper clip supports, making sure the stripped ends of the coil are touching the clips.
10. If all is well, the coil should start to oscillate. It might need a little push to start.

Figure 1

Figure 2


1. Take apart an unplugged general appliance with an electric motor like a fan and try to identify the bar magnets and coils. Can you see how it works like your coffee cup motor?

Created April 24, 1997 by Danica Nuccitelli.
Maintained by
Last updated April 24, 1997.