Download Make a Motor

Make a Motor
Activity Goal
To show examples of how magnets and electricity work together to make simple motors.
NGSS Domain(s)
PS3.A Definitions of Energy
PS3.B Conservation of Energy and Energy Transfer
PS3.C Relationship between Energy and Forces
Related Invention
• Electric Motor
History and Context of Activity (background information for museum staff)
The development of the electric motor begins with Michael Faraday (1791–1867), a brilliant
chemist, physicist, and inventor. Though he received only a basic education and had little
understanding of complex math such as calculus and trigonometry, he made numerous
discoveries through reason and experimentation.
Faraday built on work by other scientists such as Hans Oersted’s discovery of electromagnetism
in 1820, and in 1821 Faraday demonstrated the first example of an electric motor. With it he
showed that electrical energy could be converted into mechanical energy. This early motor
consisted of a free-hanging wire whose end was dipped into a dish of mercury. A magnet was
placed in the mercury. When a current from a battery was run through both the wire and the
mercury, the free-hanging wire would swing in circles around the battery indicating that the
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current caused a close circular magnetic field around the wire.
This first kind of motor designed by Faraday is known as a homopolar motor. It has electric
current and a magnetic field that is along the axis of rotation but is limited to being able to turn
just one coil and, therefore, doesn’t have a lot of useful applications. It also has current running in
just one direction, which is known as DC (direct current.) Motor #1 in the activity below is a type
of homopolar motor.
Another related kind of motor, as seen in Motor #2, also uses magnetism and electricity to turn a
coil. There is a stationary magnet and an electromagnet that can be turned on and off in a way to
cause it to spin. In the activity below the spinning is a result of the copper wire in the coil being
partially insulated. However, in other more complex motors, the current is actually turned on and
off or the magnetism is continually reversed, and as a result, the electromagnetic coil is
continually attracted in different places and spins accordingly. Because the changes direction
within the motor, this is known as AC (alternating current).
Supplies
Motor #1 (simpler)
•
One C or D size battery
•
One or more small disc-shaped neodymium magnets (it may require more than one
magnet, depending on strength). Disc shaped is ideal because it will allow the motor to
spin smoothly.
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A metal screw or nail (make sure it has a pointed tip)
•
Approximately 15–20 cm (6–8 inches) of coated or bare copper wire, between
0.8 mm–2.0 mm thick (#20–#12 gauge, United States)
•
(Optional) Wire strippers, if using coated wire
•
(Optional) Adhesive tape
Motor #2 (more complex)
•
Around 50 cm (1.5 feet) of coated or enameled copper wire between 0.8 mm–2.0 mm
thick (#20–#12 gauge, United States). You may wish to experiment with different lengths
or thicknesses of wire to see which work best.
Note: Bare copper wire will NOT work.
•
One AA battery, a thick pen, or some other cylindrical object of similar width
•
Wire strippers
•
A sharp knife or single razor
•
One D size battery (C batteries may not have enough power)
•
At least one rubber band
•
Two large paper clips
•
One or more small, strong magnets
•
(Optional) Small pliers
•
Adhesive tape
Safety Notice:
• When using wire, pointed screws, or nails, take precautions so that visitors
(particularly children) do not poke themselves.
• If using strong magnets, be aware that two strong magnets snapping together
can cause painful pinching of skin.
• Keep magnets away from cell phones and other electronics.
Advance Preparation
Motor #1
If you are using coated copper wire, strip about 12 mm (0.5 inches) of coating from each end.
Test the motor at least once before showing visitors to insure that the battery charge and magnet
strength are sufficient.
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Motor #2
It is recommended that you assemble this motor before taking it onto the exhibition floor to
interact with visitors. Coiling and stripping the wire can take a bit of time, and you may want to
make sure the motor works first.
There are many pictures and videos of this kind of motor available online with some requiring
more tools and planning. This is a simple version of this motor, but a quick online search of terms
such as “battery, motor, and magnet” will help you find other, more elaborate motor designs.
1. Wrap the copper wire around the battery or thick pen, creating a coil similar to the one
pictured below. Leave around 5 cm (2 in) sticking out from either side of the coil, and
make sure the two ends are directly opposite each other.
Note: You can wrap the ends of the wire around the inside of the coil to make it hold together
better and/or look cleaner (as pictured below), but it’s not required. The pliers may make the
wrapping and coiling easier.
Picture #1
2. Use the wire strippers to remove the coating on ONLY ONE of the ends
3. Lay the other end on a table or flat surface and carefully use the sharp knife or razor to
scrape off only half of the coating, leaving the other half of the coating intact
Picture #2
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4. Wrap the rubber band around the battery so it wraps lengthwise around both the
positive and negative ends.
5. Bend the paperclips to form a support for the coil. There is no correct way to bend
them, but something like the picture at right will work.
6. Use the adhesive tape to tape down the battery to the table to keep it secure.
7. Slip the paperclips under the rubber bands, one each on both the positive and
negative ends of the battery so that the hook end of the paperclip sticks up
vertically. Make sure the two paperclips stick up to about the same height.
8. Stick the magnet(s) to the side of the battery just in between the two paperclips.
9. Hang the coil on the paperclip supports. The two ends of the coil—the bare side
and the side with half of the covering removed—should both be in contact with
the paperclips.
Picture #3
10. Give it a little spin!
Note: If it doesn’t spin, try one or more of the following:
• Try spinning the coil the other direction. It will only spin one way.
• Make sure the coil is in contact with the paperclips.
• Make sure that one of the coil ends has half of the covering still intact.
• Add more or stronger batteries.
• Make sure the each of the paperclips are securely touching their respective ends of the
battery.
• Make sure the battery has a charge.
Introducing the Activity (background information for visitors)
What do blenders, DVD players, remote control cars, washing machines, and computers have in
common? They all contain electric motors! In fact, you can probably find 30+ small electric motors
in appliances and gadgets in your house alone.
So how do electric motors work? Most electric motors (including the two in this activity) have two
key components: magnetism and electricity. If you’ve ever played with magnets you probably
know that they have a magnetic field with a north pole and a south pole. If you try to push the
north poles of two magnets together, the magnets will push apart and repel each other. The same
thing will happen if you try to push the south poles of two magnets together. If, however, you
bring the north pole of one magnet close to the south pole of another, they will attract each other
and stick strongly together—opposites attract!
The electricity for a motor can come from a battery or some other source of power. When the
electricity in a motor is turned on, it will send a current through a wire in the battery and turn that
wire into an electromagnet.
So how does that make a motor work?
An electric motor uses the attraction and repelling properties of magnets to create motion. An
electric motor contains two magnets:
• A stationary magnet that stays in a fixed position in the motor
• A temporary magnet that is created when current runs through a wire (electromagnet)
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Motor #1 is a kind of homopolar motor, meaning that the polarity of the motor does not change
(the positive and negative sides of the motor always stay the same). When you touch the wire
from the top of the battery to the magnets below, electromagnetic force is created. That force
runs parallel (the same direction) to the battery, and that is also parallel to the magnetic field
caused by the current running through the wire. When this happens, there is a push out
perpendicular (at a 90 degree angle) from the direction of the magnetic field, and that push is
what causes the magnet to spin.
In Motor #2, since the stationary magnet doesn’t move, its north and south poles point in the
same direction all the time. On the other hand, the temporary magnet is an electromagnet and
only has a magnetic field when current is running through it, and the strength of the temporary
magnet can be changed depending on how much current it has and how many coils are in the
wire.
The basic structure of Motor #2 consists of a power source (battery), a stationary magnet, a
copper coil, and supports to hold up the coil. When you attach all of the parts together, the
electricity will flow out from the battery, up through the support, through the coil, and back down
the other support to the other side of the battery. When the electricity is flowing through the coil, it
temporarily turns it into an electromagnet that is attracted and repelled by the stationary magnet.
If you up the motor with the battery, magnets, and supports as in in Motor #2 and place the coil
into the two supports as directed, the electricity will flow and the coil will be turned into an
electromagnet. Now the coil will be attracted to the stationary magnet and will turn to become
aligned with it. Since the end on one side of the coil still has coating on half of it, when the coil
turns, the coating breaks the magnetic attraction briefly and the electromagnet shuts off.
However, since the coil has momentum, when it turns just a bit more so the bare wire is touching
again, it will be attracted to the stationary magnet again, and it will keep spinning. In essence, the
coil is spinning because the electromagnet is being turned on and off in pulses.
Doing the Activity
Motor #1
Snap the small disc-shaped magnet to the head (flat end) of the screw/nail.
Hold the pointed tip of the screw/nail up to either the positive or negative end of the battery. The
screw/nail and magnet should be attracted to the battery and should hang on their own. If they do
not hang properly, you may need to do one of the following:
• Add more batteries
• Remove batteries if the screw/nail/battery combination is too heavy
• Get a stronger battery
Take one end of the copper wire and touch it to the top of the battery on its free terminal (the
opposite side of the battery from where the screw/nail is hanging). Take the other end of the wire
and touch it to the side of the magnet. The screw/nail and magnet will start spinning. There may
even be a few small sparks!
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Picture #4
Hints:
•
•
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Center the screw/nail head in the middle of the magnet disc for more symmetrical
rotation.
You may find that it spins more easily if you just touch the very end of the wire to the
battery.
You may wish to tape the copper wire to the top of the battery to more easily hold it in
place, but it’s perfectly safe to hold it with your hand if you wish.
Motor #2
See instructions in Advance Preparation above. You can take the motor apart and let the
visitors put it back together or simply use it as a demonstration device to talk about motors.
Questions to Ask Visitors
Besides an automobile, can you think of something that has a motor in it? (Example:
household appliances such as blenders or washing machines.)
Once you got a motor spinning, what could you do with it? (Example: attach a belt to it and
turn a wheel.)
How long do you think these motors would last? How would you make them last longer?
_______________________
“Make a Motor” is based, in part, on the activity entitled “Make a Motor” from the book Science
Rocks, by Ian Graham (New York: DK Publishing, 2011) pp 116–117.
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http://en.wikipedia.org/wiki/Electric_motor
Pictures #1 and #2 are from http://www.simplemotor.com/bmotor.htm
Picture #3 is a sketch by the author of this activity
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Introducing the activity is largely based on text from: http://www.sciencebuddies.org/sciencefair-projects/project_ideas/Elec_p051.shtml
Picture #4 is from http://en.wikipedia.org/wiki/Homopolar_motor
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