A bigger motor
Our next motor is simply a larger version of the first one, with a base
made of wood like this:
In the middle of the base we have placed the magnet. Around the magnet
we have drilled four small holes for the support wires.
We wind the coil using thick wire (this wire is 20 gauge enameled copper
wire). We use a "D" cell as the coil form:
We use brass wire for the supports, and we make all the connections under
the base, so everything looks nice and neat. For a battery connection,
we use a 9 volt battery clip.
The finished motor looks like this:
How does it work?
When electricity flows through a coil of wire, the coil becomes
. An electromagnet acts just like a
regular magnet. It has a north pole and a south pole, and can
attract and repel other magnets.
Our coil becomes an electromagnet when the bare copper half of the
armature wires touch the bare wire of the supports, and electricity
flows into the coil. The electromagnet has a north pole which is
attracted to the south pole of the regular magnet. It also has
a south pole that is repelled by the south pole of the regular
When we scraped off the insulation from the armature wires, we were careful
to do it with the coil standing up, and not lying flat on the table.
This makes the poles of the electromagnet point to the left and right
(as if there was an invisible regular magnet that had the wire wrapped
around it). If the coil was flat on the table, the poles would point
up and down.
Since the poles point left and right, they have to move in order to line
up with the magnet at the bottom, whose poles are aligned up and down.
So the coil rotates to line up with the magnet. But once the coil is
exactly lined up with the magnet, the insulated half of the wire is now
touching the supports instead of the bare half. The electricity is cut
off, and the coil is no longer an electromagnet. This leaves it free
to coast on around until the bare copper can again touch the bare support,
and start the whole process over again.
A faster motor
One easy way to make the motor run faster is to add another magnet.
Hold a magnet over the top of the motor while it is running.
As you move the magnet closer to the spinning coil, one of two things
will happen. Either the motor will stop, or it will run faster.
Which of these happens will depend on which pole of the magnet you
have facing the coil. Make sure you hold the motor down so the magnets
will not jump together and crush the little motor!
There is another way to speed up the motor. The motor only gets electricity
during half of the cycle. During the other half, the insulation blocks
the flow of current. This is necessary because once the coil has spun
around to face the magnet, if we let the current continue to flow, it will
stay stuck there, facing the magnetic pole to which it is attracted.
But suppose instead of just stopping the current, we reversed it, so the
north pole of the electromagnet became the south pole, and vice versa.
The coil would want to flip over again!
And since it is already going in one direction, that is the direction
it will choose to continue going (due to the inertia and momentum of the
Now all we need to do is to figure out how to get the current to reverse,
and how to get it to happen at the right time.
It turns out to be pretty easy. Place the motor in front of you, so that
the axle goes left to right. Now attach a bare wire to the left support, and
let it rest on the right axle, just past the right support. Do the same
thing with the right support and the left axle.
On one half of the cycle, the bare half of the axle will face down and
touch the bare wire of the support, just like before. On the other half
of the cycle, the bare half of the axle will touch the new wires that are
resting on top of the axle. Since these wires are connected to the opposite
supports, the current will flow in the opposite direction. The motor will
get two kicks per cycle instead of one, and will never be coasting, it will
always have power. It will go twice as fast.
Below is a photo of a motor built this way. The connections are hidden
underneath the base for neatness, but you can see the wires resting on
the top of the axles, and know that they are connected to the opposite
Below is a closeup view of the same motor. Notice that there are two
tiny glass beads placed on the axles. These beads speed the motor up
even more, as they reduce the friction of the armature against the
supports. Since this reduction in friction balances the extra friction
of the new wires, the motor still goes about twice as fast as the older,
A 10 minute motor with no magnet.
For more information on electromagnetism, see the
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Simon Quellen Field