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Project Summary

Difficulty	5  –  7
Time required	Average (about one week)
Prerequisites	None
Material Availability	Readily available
Cost	Low ($20 - $50)
Safety	Use caution when using a sharp knife or wire cutters. Never try to use a wall socket as a source of power for your motor.

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Abstract

Objective

To learn how to build a simple electric motor and to determine which motor design produces the fastest rate of spin.

Introduction

So, what do windshield wipers, CD players, VCR's, blenders, ice makers, computers, and talking toys have in common? They all contain electric motors! In fact, if you walk through your house, it is possible to find as many as 50 electric motors hidden in electrical devices, appliances, and toys in every room in your home. They are a very important and vital part of modern life.

Have you ever played with magnets before? If so, you are well on your way to understanding how simple electric motors work. Magnets have a magnetic field with a north pole and a south pole. If you play with two magnets and try to push the north poles of each magnet together, the magnets will not go together. They will repel each other. The same thing happens if you try to push two south poles together. If two poles are the same, they will repel each other. If, however, you play with two magnets and bring the north pole of one close to the south pole of another, they will attract each other and stick strongly together—opposites attract!

An electric motor uses the attraction and repelling properties of magnets to create motion. An electric motor contains two magnets: a permanent magnet (also called a fixed or static magnet) and a temporary magnet. The temporary magnet is a special magnet, called an electromagnet. It is created by passing an electric current through a wire. The permanent magnet has a magnetic field (a north pole and a south pole) all the time, but the electromagnet only has a magnetic field when current is flowing through the wire. The strength of the electromagnet's magnetic field can be increased by increasing the current through the wire, or by forming the wire into multiple loops.

To make an electric motor, the electromagnet (the temporary magnet) is placed on an axle so it can spin freely. It is then placed inside the magnetic field of a permanent magnet. This is when things get interesting! When a current is passed through the electromagnet, the resulting temporary magnetic field interacts with the permanent magnetic field and attractive and repelling forces are created. These forces push the electromagnet (the loops of wire), which is free to spin on its axle, and an electric motor is born.

Which direction the loops of wire are pushed in can be predicted by Fleming's Left Hand Rule for Motors. Hold your left hand out, as shown in Figure 1.

Figure 1. This drawing shows Fleming's left hand rule for motors. (ExplainThatStuff.com, 2008.)

Your pointer finger represents the direction of the field (from north to south) of the permanent magnet. Your middle finger represents the direction of the electric current (which flows from the positive terminal of the battery to the negative terminal of the battery). The direction of the force on the loop of wire (the electromagnet) is predicted by the direction of your thumb. The thumb, therefore, tells you which direction the electromagnet will spin. Try Fleming's Left Hand Rule on the example in Figure 2 and see if your thumb predicts the direction in which the electromagnet will rotate.

Figure 2. This animation shows the direction the loop of wire (the electromagnet) will rotate, based on Fleming's Left Hand Rule for Motors. (ExplainThatStuff.com, 2008.)

Terms, Concepts and Questions to Start Background Research

• Electric motor
• Magnet
• Magnetic field
• Repel
• Attract
• Permanent
• Static
• Temporary
• Electromagnet
• Axle
• Fleming's Left Hand Rule for Motors
• Insulate
• Beakman motor

Questions

• Where can you find electric motors? How many can you count in your home?
• What happens when two magnets get close together?
• What is the difference between a permanent magnet and a temporary magnet?
• How do you make a temporary magnet (an electromagnet)?
• How can you increase the strength of an electromagnet?
• What are the parts of a simple electric motor? Which of those parts can spin?
• What causes the spinning an electric motor?
• What does Fleming's Left Hand Rule for Motors tell you?

Bibliography

These sources show the parts of a simple electric motor, how they work, and where to find them:

• Woodford, C. (2007, June 27). Electric Motors. Retrieved August 26, 2008, from http://www.explainthatstuff.com/electricmotors.html
• Brain, M. (2008). How Electric Motors Work. Retrieved August 26, 2008, from http://electronics.howstuffworks.com/motor.htm

This source provides troubleshooting advice for Beakman motors:

• Pozmantir, S. (2007). Assembly Instructions: Conventional Motor (Beakman's Motor Kit). Retrieved August 28, 2008, from http://www.simplemotor.com/bmotor.htm

How to calculate the rate of motor spin using a voltage probe is described in the following source:

• Lamore, B. Measuring Motor Speed. Retrieved August 29, 2008, from http://www.vernier.com/innovate/innovativeuse93.html

Materials and Equipment

Many of the following parts can be purchased at Radio Shack:

• Measuring tape or ruler
• Battery (AAA size) or ballpoint pen
• Knife
• Magnet wire, enamel-coated, 22-gauge (or thicker), Radio Shack part # 278-1345
• Piece of cardboard, about the size of a piece of paper
• Wire cutters
• Bare copper or brass wire, 18- or 20-gauge, Radio Shack part # 278-1217 or # 278-1216, or 6 straightened paper clips
• Nail, small
• Battery holders, Radio Shack part # 270-402 (holds a "C" cell) or # 270-403 (holds a "D" cell) (3)
• Batteries to fit the holder, C or D cell, depending on your battery holders (3)
• Strip of paper (3)
• Magnet, Radio Shack part # 64-1877, # 64-1895, # 64-1883, # 64-1879, or # 64-1888 (3)
• Voltmeter
• Lab notebook

Experimental Procedure

You will be building and comparing three simple electric motors, called Beakman motors. The first motor will have 10 coil windings, the second will have 30 coil windings, and the third will have 50 coil windings.

Building Your Electromagnet

1. Measure out about 2 inches of magnet wire, and from that point on, begin winding your magnet wire 10 times around the AAA battery or ballpoint pen. Cut the wire with the wire cutters, leaving about 2 inches free (uncoiled) at each end.
2. Carefully slide the loops of wire off the AAA battery or ballpoint pen.
3. Now you need to wrap the loops so that they stay bunched together and form a tight coil. Wrap each free end of wire around the loops of coil two times in the 3 o'clock and 9 o'clock positions, as shown in Figure 3. If desired, you can then knot the wire to help the coils stay tightly bunched. The free ends of the magnet wire should form a straight line through the coil. The free ends will be the axle upon which your electromagnet (the loops of wire) spins.

Figure 3. This drawing shows how the electromagnet and the axle that it spins on will look when it is formed.

4. Using a sharp knife, strip off the insulating material on half of the axles, as shown in Figure 4. The easiest way to do this is to hold the coil between your thumb and forefinger so it is standing upright (the coil is perpendicular to the floor) and then hold the coil off to one side of a table. (If you want to see an image of how to hold the coil, view the sixth figure in these assembly instructions for a Beakman motor.) Lay the axle on a piece of cardboard (to protect the table underneath) and scrape off the top half of the wire with a knife. Be careful not to press too hard when you are scraping or you might cut the wire or cut into the table. Flip the coil around and then scrape the other axle. Scraping off half of the insulating material is done to provide a period of time when current can flow through the coil and create a temporary magnetic field, and a period of time when it cannot. When the bare copper of the axle is rotated down, bare copper will be touching the axle supports, and current will flow to the coil, creating a temporary magnetic field. When the bare copper is rotated up, insulated copper will be touching the axle supports, and no current will flow to the coil.

Figure 4. This drawing shows the parts of the axles to strip of insulating material.

Building Your Axle Support

1. With the wire cutters, cut two equal lengths of stiff, bare copper or brass wire, approximately 3-4 inches long. Two straightened paper clips are also possible alternatives.
2. Bend each wire around a small nail to form a loop. Slip the wires off the nail. Now each axle support should look like the end of a safety pin. Each one should look like a loop with two legs.

Building Your Electric Motor Base

1. The battery holder makes a good electric motor base because it is heavy and stabilizes the electromagnet as it spins. Wind the free ends of your axle supports (the two legs) into the holes in the plastic at each end of the battery holder, as shown in Figure 5.

Building Your Electric Motor

1. Insert each axle into an axle support. Adjust the axle supports so that they are close to the coil, but not touching it.
2. Place the magnet on top of the battery holder, below the coil. Give the coil a few turns to makes sure it can spin freely and does not rub against the magnet.
3. Place the battery and a strip of paper inside the battery holder. The strip of paper is the on/off switch. When the paper is in place, it acts as an insulator and prevents current from flowing (the switch is off). When you pull out the paper, current can flow. It is like turning the switch on. Your finished electric motor should appear similar to the setup shown in Figure 5.

Figure 5. This drawing shows how to connect the electromagnet and its axles, the permanent magnet, axle supports, battery, and its paper switch to form a simple electric motor.

4. Repeat the steps Building Your Electromagnet through step 3 of Building Your Electric Motor, replacing the 10 windings with 30 windings, to form your second electric motor.
5. Repeat the steps Building Your Electromagnet through step 3 of Building Your Electric Motor, replacing the 10 windings with 50 windings, to form your third electric motor.

Testing Your Electric Motors

1. Use Fleming's Left Hand Rule for Motors to predict which way the motor should spin.
2. Remove the strip of paper from your first motor. The electromagnet should start to spin on its axles. If it does not, consult the Bibliography for troubleshooting tips. Write down the direction of spin in your lab notebook. Just for fun, flip the magnet over. What direction does the motor spin now? Does this agree with Fleming's Left Hand Rule for Motors?
3. Use the voltmeter to measure the voltage across the axle supports and record your measurement in a data table, like the one below, in your lab notebook.
4. Measuring the speed of the motor (in revolutions per minute [rpm]) is difficult without specialized equipment, such as a voltage probe or an oscilloscope, but visually inspect your motor and describe whether it is spinning at a slow, medium, or fast rate of speed. Record your observation in your data table.
5. Replace the strip of paper to stop the motor from spinning.

Trial 1 Data Table

6. Repeat steps 2-5 of Testing Your Electric Motors for the other two motors.
7. Repeat steps 2-6 of Testing Your Electric Motors two more times for each motor, for a total of three trials each. Record your data in two additional data tables.
8. Average and record the voltages for each motor from each of the data tables.

Average Voltage Data Table

9. Which motor spun the fastest? Which motor spun the slowest? Was the average voltage lower for the fastest spinner?

Variations

• Evaluate different coil shapes. Do circular loops of wire work better than square loops of wire?
• Evaluate different magnets. Do stronger (or multiple) magnets make the motors spin faster than weaker magnets?
• Use a voltage probe, digital multimeter (set to measure frequency), or an oscilloscope to calculate the rate of motor spin for each motor, as described in the following source. How to calculate the rate of motor spin using a voltage probe is described in this Vernier source.

• For more science project ideas in this area of science, see Electricity & Electronics Project Ideas.

Credits

Kristin Strong, Science Buddies

The simple electric motor design described in this science fair project follows the materials and procedure presented in:

• Field, S. Q. (2007). Science Toys You Can Make with Your Kids. Retrieved August 27, 2008, from http://scitoys.com/scitoys/scitoys/electro/electro.html

This project was inspired by a 2008 California State Science Fair Science Buddies Clever Scientist winner:

• Weis, C.J. (2008). Electric Motors Are Everywhere! Retrieved August 28, 2008, from http://www.usc.edu/CSSF/Current/Projects/J0837.pdf

Last edit date: 2008-11-10 11:39:00

Career Focus

If you like this project, you might enjoy exploring careers in Electricity & Electronics.

	Electrician Electricians are the people who bring electricity to our homes, schools, businesses, public spaces, and streets—lighting up our world, keeping the indoor temperature comfortable, and powering TVs, computers, and all sorts of machines that make life better. Electricians install and maintain the wiring and equipment that carries electricity, and they also fix electrical machines.			Electrical and Electronics Engineer Just as a potter forms clay, or a steel worker molds molten steel, electrical and electronics engineers gather and shape electricity and use it to make products that transmit power or transmit information. Electrical and electronics engineers may specialize in one of the millions of products that make or use electricity, like cell phones, electric motors, microwaves, medical instruments, airline navigation system, or handheld games.
	Electrical Engineering Technician Electrical engineering technicians help design, test, and manufacture electrical and electronic equipment. These people are part of the team of engineers and research scientists that keep our high-tech world going and moving forward.			Semiconductor Processor What do traffic lights, lasers, and microchips have in common? They are made from special materials called semiconductors. Semiconductors have helped revolutionize technology. If you enjoy hands-on work and are interested in participating in cutting-edge semiconductor technology, then a career as a semiconductor processor maybe of interest to you!

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