The objective of this experiment is to demonstrate how electricity can
be used to make a motor. This helps us to see how
electrical energy is converted into mechanical energy. It also allows
the user to see a practical application of electromagnetism.
Several feet of wire
Empty spool of thread
Two strong permanent magnets
Two identical nails
1 ft by 1 ft board
6 Volt Battery
How to Build It
Sharpen a long pencil at both ends. This will serve as our rotor axle.
The spool should fit perfectly around the pencil. Take the two nails and
tape them, point to head, around the pencil. Wrap the wire around the nails
as shown in the diagram. Pay close attention to the direction the wire
is wrapped around the nails. The spool will be our commutator. The aluminum
foil should be prepared in the following way. It should be fit in two strips
around the spool. Each strip should be exactly the same length. The strips
should be approximately one-eighth of an inch apart. Before taping the
aluminum to the spool, strip the wire ends which are wrapped around the
nails and place them on opposite sides of the commutator as shown in the
diagram. The ends stay in place better if placed beneath the foil. Align
the one-eighth inch separations with the nails before securing them to
the commutator. The sharpened pencil ends will serve as makeshift bearings
for the rotor. Make small indentations in two pieces of wood that will
support the rotor and allow it to spin freely. There should be as little
friction as possible. The rotor should spin several times with only a slight
Up until now, our instructions have followed the
diagram. In order to produce an easier to assemble and more functional
motor, we will now vary from the diagram. The leads to the commutator should
be as shown in the diagram—facing directly upward, and slightly touching
the aluminum foil. Instead of connecting these leads to the other nails,
simply connect them directly to the terminals of the battery. The permanent
magnets replace these nails.
Attach the leads to the battery as shown in the diagram. Hold the two
permanent magnets about one centimeter away from the ends of the nails
on the motor when they are parallel to the ground. If offset a little bit,
the motor should start to work on its own. If not, it could require a small
push to get it going. The motor should now run smoothly as you hold the
magnets in their proper position.
If there does not appear to be any current through the motor,
try the following:
If it appears that there is no current through the motor, you probably
have a break in the circuit. Check the wire ends, which are connected to
the aluminum foil, to see if they are still connected. Make sure that some
of the exposed wire is in contact with the aluminum.
- Try holding a small paper clip or other small metal object close
to the ends of the nails. If there is a current flowing, then the nails
should act as electromagnets.
- Check the leads to commutator to see if they work. This can be done
with a multimeter, or any device which allows you to see if current is
present. You could attach the leads to a small light bulb, or even to an
electromagnet. This should tell you if you have current passing through
If there is current in the motor, but the motor still will not run,
try the following:
Questions for Thought
- Spin the motor manually. If it does not spin very well, then there
is probably too much friction. Try laying the pencil ends across some other
object in order to get better spin and less friction.
- Hold the magnets at slightly different angles. Try holding different
sides of the magnets to the motor. Experiment with different angles and
- Make sure that the breaks in the aluminum foil are aligned with the
- Give the motor a good push to start it spinning.
- Make sure that your battery is not drained because it has been attached
to the circuit for too long.
- Try a more powerful battery. This can be done by connecting several
batteries in series with each other.
- What makes the motor run?
- ANSWER: The coils around the nails attached to the shaft of the motor
act as electromagnets. The leads to the commutator send current running
through the wires wrapped around the nails, and convert those nails into
electromagnets with poles. Each electromagnet has either a north or south
pole at its end, depending on the direction of the current. When the spin
of the motor causes the wire lead on one side of the commutator to come
in contact with the other strip of foil, the current changes direction.
This is why during half of its turn the electromagnet on one side of the
nails is attracted to the permanent magnet, and during the other half it
is repelled. This attracting and repelling action is what causes the motor
- How can I make the motor spin faster or slower?
- ANSWER: In order to make the motor spin faster or slower you must increase
or decrease the strength of the magnetic field. This is done by either
changing the amount of current running through the motor or varying the
distance of the permanent magnets from the motor.
- The Crazy Cantilever and Other Science Experiments
by Robert Kadesch, Harper and Brothers, 1961, pp.102-107.
- More Science Projects You Can Do by George K. Stone, Prentice-Hall,
1970, p. 98.
Last Updated: June 21, 2002
Original Page Development by: Matt Dayley and Keith Holbert
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