To show examples of how magnets and electricity work together to make simple motors

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 En...
Author: Jessie Boyd
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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 1 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. 101 Inventions: Make a Motor Page 1 of 8



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. 101 Inventions: Make a Motor Page 2 of 8

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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 #2 101 Inventions: Make a Motor Page 4 of 8

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) 101 Inventions: Make a Motor Page 5 of 8

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: • • •

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. 1

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 101 Inventions: Make a Motor Page 7 of 8

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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