SIMPLE DC MOTOR
What You Need:
What You Do:
- To make a bundle, wrap each end of wire several times around the
loops to hold them in place. Position the ends so they are directly
across from each other and extending out in a straight line on either
side of the bundle, to form an axle. What you just made is called the armature.
- Hold the wire bundle you have made so that it would be flat against
a wall, rather than a table, and color the top side of each wire end
using the marker. Leave the bottom side of each wire bare.
- Carefully bend each paperclip, forming a small loop by wrapping one
end around a small object such as a pencil or pen. Thick wire and
pliers may be used instead of a paper clip if you want. Be sure to use
caution when using the pliers.
- If you are using a battery holder, attach a paper clip to either
side, and insert the battery. If you don't have a battery holder, wrap
the rubber band tightly around the length of the battery. Insert the
paperclips so each one is touching one of the terminals, and they are
securely held by the rubber band. Attach the curved side of the battery
firmly to a table or other flat surface using the clay or sticky tack.
- Set one neodymium magnet on top of the battery, in the center.
Position the armature in the paper clip loops, with the shiny, uncolored
side touching the paperclips. Make sure it doesn't touch the magnet.
- If your motor doesn't start immediately, try giving it a start by
spinning the wire bundle. Since the motor will only spin in one
direction, try spinning it both ways.
- If your motor still is not working, make sure that the paperclips
are securely attached to the battery terminals. You may also need to
adjust the insulated wire so both ends are straight, and the bundle you
have made is neat, with the wire ends directly opposite of each other.
- With the motor spinning, hold up the other magnet, above the
armature. As you move it closer, what happens? Turn the magnet over and
try again to see what happens.
What Happened:
The armature is a temporary magnet, getting its force from the
electrical current in the battery. The neodymium magnet is permanent,
meaning that it will always have two poles, and cannot lose its force.
These two forces - electricity and magnetism - work together to spin the
motor. The poles of the permanent magnet repel the poles of the
temporary magnet, causing the armature to rotate one-half turn. After a
half-turn, the insulated side of the wire (the part you colored with
permanent marker) contacts the paperclips, stopping the electric
current. The force of gravity finishes the turn of the armature until
the bare side is touching again and the process starts over.
The motor you created uses direct current, or DC, to rotate the
armature. The magnetic force is only able to flow in one direction, so
the motor spins in only one direction. AC, or alternating current, uses
the same principle of electron flow, but the pole is rotating rather
than in one place. AC motors are often more complex than DC motors,
like the simple one you were able to make. Unlike a fixed DC motor, AC
motors can switch the direction of rotation. (The DC motor you made is
only able to spin in one direction because its direction is determined
by the poles of the permanent magnet. If you turn the magnet over, so
the other pole is facing up, it will change the direction the motor
spins.)
When you held the second magnet over the top of the armature, it
either stopped or made the motor rotate more rapidly. If it stopped,
it's because the pole was in the opposite direction of the first magnet,
in a sense canceling out the rotation of the armature. If it moves
faster, the same poles of the first and second magnets, which repel each
other, work to spin the armature more quickly than with only one
magnet.
Building Bigger, Faster Motors
Experiment with batteries of higher voltage, as well as more powerful
magnets. You can also try using ceramic magnets. One design we found
worked well was to set the armature over 4 ceramic ring magnets and
connect the supporting paperclips to a 6V battery. You can also try
increasing the size of the armature, and how many coils there are, to
make a stronger electromagnet. When using batteries of higher voltage,
and bare wires, be very careful. The circuit can emit enough heat to
cause a burn if the wire is held too long.
