1. How to Make a Simple DC Motor

2. You will need:
 Magnet wire
 A Magnet
 Styrofoam base
 9-volt battery
 2 paperclips
 2 test leads (w/ alligator clips)
 “C” size battery
 Sandpaper or razor blade

3. Some Basic “Need to Know’s”
 A motor converts electrical energy into mechanical
energy.
 When current is flowing through a coil of wire in a
magnetic field, a force (torque) is induced.
 The strength of this force depends on three things:
 Amount of current
 Length of wire
 Strength of the magnet
 You can determine the direction of the force by using
the three-finger rule.

4. The Three-Finger Rule
 Shape your right hand as
shown at the right:
 index finger is pointing
straight forward
 thumb is pointing up at a
right angle to your index
finger
 middle finger is pointing
straight out from the
plane of your palm.
 With your hand in this
shape, you are ready to
use it!

5. The Three-Finger Rule (cont.)
 Point index finger in the
direction of the magnetic field
(the direction of the arrows,
for this example).
 Point your thumb in the
direction the current is
flowing.
 Your middle finger will then
be pointing in the direction of
the force.
 Using the 3-finger rule, figure
out the direction of the force
at the top of the coil, the
(Notice that the direction of the force will bottom of the coil, and which
be different at the top of the coil than at the direction the coil will spin.
bottom of the coil.)

6. The Three-Finger Rule (cont.)
 Top of coil: Force is
directed toward us (away
from the screen).
 Bottom of coil: Force is
directed away from us
(into the plane of the
screen).
 Coil will spin with the top
moving toward us. In
other words, if it were a
wheel, it would roll out
from the screen.

7. But wait…
Once the coil has spun 180 degrees, the direction of the current at the top
of the coil will be flowing the opposite direction than at the beginning, as
shown below, because the bottom is at the top.
•Assuming that the magnetic field still points up, which way will the coil
spin now?
•How might this cause the motor to be ineffective?

8. Understanding the Problem
In order to solve this problem, we need to
understand what causes the problem:
 Current can only flow through a wire if
there is a connection. This means that
we need to remove the enamel coating
so that the copper wire can make a
direct connection with the paperclips.
 If we completely remove the enamel
coating from both ends, the current will
flow continuously. This will result in a
coil of wire that wobbles back and forth,
rather than a motor that spins as it
should.

9. Solving the Problem
 By removing only part of the Cross-section
enamel on each side of the coil, we of magnet wire
can control when the current flows
and when it doesn’t.
 If the current is not flowing, there Copper
will be no force to make it spin. Wire
 In order to make the motor work
properly, we need to remove the
Enamel coating
enamel coating from only half of
the wire, as shown at the right. The current only flows for one half
 Each time the coil reaches a of a revolution. The other half of the
connection point, current flows revolution receives no current (and
through the wire. The coil, then, therefore, no force) but continues
experiences a force in the same spinning because of momentum.
direction each time. This allows the This is repeated so the motor will
motor to spin properly. spin until disconnected.

10. Let’s test it!
 Coil the magnet wire
around a “C-size” battery
12-15 times. Leave about
2 inches on each side of
the coil.
 Next, we need to remove
the enamel from the wire
so that current can flow.
WAIT—not all of it!

11. Removing the Enamel
 To remove only half of one
side, hold the wire on a table
so that the coil is oriented
vertically.
 Use a file, blade or sandpaper
to rub off the TOP SIDE of the
wire only. To ensure a good
connection, completely
remove the enamel on the top
half of the wire from the base
of the windings (near the coil)
through the end.
 Now turn the coil around and
remove the enamel
completely from the other end
(top, sides, and bottom).
Again, make sure it is clean
for a good connection.

12. Preparing the Paperclips
 Bend your paperclips in the
succession to the left.
 They should end up looking
something like the ones below.
 It’s easiest to use pliers if
available, but not necessary.

13. Preparing Your Base
 Put your magnet in the
center of your Styrofoam.
 Trace around the magnet
with a blade or knife.
 Remove the inner portion
of Styrofoam.
 Replace Styrofoam with the
magnet. Try to get the
magnet as flush with the
top of the Styrofoam as
possible for a flat base.
 Put your paperclips in
place, as shown in the
picture.

14. On Your Mark, Get Set…
 Place your coil in the
center of the paperclip
holders, making sure the
ends are parallel to the
base.
 If possible, use a
voltmeter to test the 9-
volt battery to make sure
it is good. (If not
possible, we’ll find out in
a second.)

15. Give It a Whirl!
 Connect one end of each
alligator clip lead to the
battery terminals of the
9-volt battery (one to
negative, one to
positive).
 Connect the other ends
of the leads to one side of
each paperclip, as shown.
 If your coil does not spin
at first, give it a little
push start.

16. Doesn’t work?
Some possible problems:
 Was the enamel removed correctly? (The copper should be
exposed completely on one end but only on the top of the other end of
the coil.)
 Is the enamel removed enough to make a clean
connection? (The copper should be shiny and without spots of
enamel still attached.)
 Is your battery providing power? (Use a voltmeter to test it.)
 Is the circuit complete? (Current should flow from the negative
terminal of the battery  one side of a paperclip  through the coil 
through the other paperclip  through the other test lead  into the
positive terminal of the battery.)
 Is the coil close to and directly above the magnet?