Electric Motor Revolutionized Human Technology

Home , Electric generator, Electric motor

INVESTIGATION A3 Collaborative Learning This investigation is Exploros-enabled for tablets. See page xiii for details.

A3 How a Motor Works Key Question: How does a motor work?

The electric motor revolutionized human technology. Materials for each group With an electric motor, power could easily be transferred yy From the Electric Motor kit: electric motor with via electricity from one place to another. The electric the battery pack, 7-8 permanent magnets, motor is based on the principles of electricity and 1 electromagnet, and the orange commutator disk magnetism. In this investigation, students learn about the parts of an electric motor and construct a working yy Four D-cell batteries* motor. They learn how permanent magnets and an *provided by the teacher electromagnet work together to cause a motor to spin. They learn that they can control the direction of spin by Online Resources changing the orientation of the magnets. Available at curiosityplace.com yy Equipment Video: Electric Motor Learning Goals yy Skill and Practice Sheets ✔ Construct a working motor. ✔ yy Whiteboard Resources ✔✔Use an electromagnet and explain how it reverses its y north and south poles. y Animation: Rotor Magnets ✔✔Determine the direction a motor will spin given the yy Student Reading: Electromagnets orientation of its magnets. Vocabulary commutator – the device that switches the direction of GETTING STARTED electric current in the electromagnet of an electric motor Time 50 minutes electric motor – a device that converts electrical energy into mechanical energy Setup and Materials electromagnet – a magnet created by a wire carrying 1. Make copies of investigation sheets for students. electric current permanent magnet – a material that retains its 2. Watch the equipment video. magnetic properties 3. Have students work in small groups of three to five. rotor – the rotating disk of an electric motor or generator 4. Review all safety procedures with students.

NGSS Connection This investigation builds conceptual understanding and skills for the following performance expectation. MS-PS2-3. Ask questions about data to determine the factors that affect the strength of electric and magnetic forces. Science and Engineering Practices Disciplinary Core Ideas Crosscutting Concepts

Asking Questions and Defining Problems PS2.B: Types of Interactions Cause and Effect

Electric Motor 15

EM_TG.indb 15 37 7/17/14 11:56 AM How a Motor Works

BACKGROUND

Electric motors convert electrical energy into A commercial electric motor that runs on batteries mechanical energy. Permanent magnets and doesn’t look quite like the spinning disk motor used in electromagnets work together to make electric motors. the investigation. However, the same three mechanisms The secret to making an electric motor work is in the are still there. The difference is in the arrangement ability of an electromagnet to reverse its north and of the electromagnets and permanent magnets. This south poles. illustration shows a small battery-powered electric motor and what it looks like inside with one end of the motor In this investigation, students first try to make the rotor case removed. spin by manually flipping permanent magnets near the rotor magnets. Next, students see how an electromagnet can be used instead. Just as with the finger magnet, the electromagnet must switch from north to south as each rotor magnet passes by to keep the rotor turning.

The device that makes this happen is called a The permanent magnets are on the outside, and they commutator. As the rotor spins, the commutator, stay fixed in place. The electromagnets are in the which is a plastic disk, reverses the direction of the rotor, and they turn. The rotating part of the motor, current in the electromagnet (when the dark and clear including the electromagnets, is called the armature. The segments of the disk interact with the photogate on armature in the illustration has three electromagnets, the electromagnet). This reversing of current makes corresponding to the three coils. the electromagnet’s side facing the disk change from north to south, and then back again. The electromagnet The wires from each of the three coils attach to three attracts and repels the magnets in the rotor, and the metal plates (the commutator) at the end of the motor turns. armature. As the rotor spins, the three plates come into contact with positive and negative brushes. Electric The three things you need to make a motor are 1) a current flows through the brushes into the coils. As the rotating part, called a rotor, with magnets that have motor turns, the plates rotate past the brushes, reversing alternating polarity; 2) one or more electromagnets; and the positive and negative connections to the coils, 3) a commutator that switches the direction of current which make the electromagnets’ magnetic poles switch in the electromagnets back and forth in the correct positions. The turning electromagnets with alternating sequence to keep the rotor spinning. poles are thus attracted and repelled by the permanent magnets, and the motor turns. The three main parts of an electric motor 1 Rotor Motors that run on AC electricity are easier to make Electromagnet because the current switches direction all by itself. Current Almost all household, industrial, and power tool motors are AC motors. These motors use electromagnets for both the rotating and fixed magnets. N

2 Fixed magnets 3 Commutator on a rotor Switches the direction of current in the electromagnet at the right time

EM_TG.indb 16 38 7/17/14 11:56 AM A3

5E LESSON PLAN

Engage Explain Ask students, “When do you think the first electric car was Revisit the Key Question to give students an opportunity built?” They may think that current designs of electric and to reflect on their learning experience and verbalize hybrid cars are a brand new green technology. Explain to understandings about the science concepts explored in students that the original electric cars were the horseless the investigation. Curiosityplace.com resources, including carriages of the 1800s. Electric motor technology has been student readings, videos, animations, and whiteboard around for over 200 years! resources, as well as readings from your current science textbook, are other tools to facilitate student communication about new ideas.

Animation Ask students, “Can you name something other than a car Rotor Magnets that has a motor?” List answers on the board. From the variety of answers, point out how many different places in Elaborate our lives we use electric motors. Electric motors transform electrical energy into mechanical energy. Have students draw all the Explore transformations of energy that take place in their electric Have students complete Investigation A3, How a Motor motors. Then have them think up and draw a type of Works. Students learn about the parts of an electric work the electric motor could do with the mechanical motor. In particular, they learn how permanent magnets energy from the output. and an electromagnet work together to cause a motor to spin. They learn that they can control the direction of Evaluate spin by changing the orientation of the magnets. yy During the investigation, use the checkpoint questions as opportunities for ongoing assessment. yy After completing the investigation, have students answer the assessment questions on the Evaluate student sheet to check understanding of the concepts presented.

Electric Motor 17

EM_TG.indb 17 39 7/17/14 11:56 AM How a Motor Works

Explore INVESTIGATION A3 Explore INVESTIGATION A3

Name ______Date ______4. Try to make the rotor spin by using your magnet to “push and pull” on the rotor magnets. It may take some time to perfect your technique because the magnets in the rotor easily jump out of the rotor and stick to the magnet in your hand. Materials: A3 How a Motor Works a. Describe how you got the rotor to spin in one direction. What did you have to do with the magnet in your ✔ 7-8 ceramic magnets hand to get the rotor to spin? How does a motor work? from the Electric Motor kit Did you know that magnets are important parts of electric motors? In this I flipped the magnet over each time another magnet passed by. My investigation, you will be using permanent magnets and an electromagnet to ✔ Electric Motor with magnet attracted the magnets in the rotor. build a simple motor and learn how magnets work in a motor. A permanent magnet the battery pack, is a type of magnet that always has its magnetic properties. An electromagnet is a an electromagnet, device that is magnetic when electricity is flowing through it. and the orange commutator disk What is an electromagnet? ✔ 4 D-cell batteries   Looking inside the electric motor Electromagnets are devices that become magnets when electricity flows through them. An electromagnet is usually made with a coil of wire wrapped around a Take your electric motor apart and set it up like the picture shows. steel or iron core. Electricity flows through the coil of wire. This causes the steel pin to become magnetized with a north and south pole. 1. First, uncover the rotor. Then, take out all the magnets. One difference between an electromagnet and a permanent magnet is that an electromagnet can reverse its north and south poles. This is done by changing the direction of the electric 2. Now, place six of the magnets in current in the electromagnet. If you know the direction the current flows, you can tell which end of the the rotor so they are evenly spaced. electromagnet is the north pole. Alternate the orientation of the north The north pole is at the top of the steel pin when the current is and south poles as shown in the picture. going counter-clockwise around the pin. The north pole is on the bottom of the pin when the current is going clockwise. 3. Put another magnet in your hand. Bring it close to the motor so that it repels a Look at the electromagnet that comes with the electric motor. magnet in the rotor. What happens? You will see a coil of copper wire wrapped around a thick steel I held my magnet so pin. The north and south pole of this pin switches when the current going through the electromagnet changes direction. The electromagnet that comes with the electric motor has a light-beam switch. Blocking the light that the north pole was beam causes the current to change direction in the coil of wire. The little green lights tell you where the north pointing toward a magnet pole is located on the electromagnet. in the rotor with its north pole facing outwards. The result was that the rotor turned clockwise, but stopped when the next magnet (with its south pole facing out) jumped out of the rotor and stuck to the magnet in my hand.

Copyright © CPO Science A3 How a Motor Works Copyright © CPO Science A3 How a Motor Works Can be duplicated for classroom use 1 of 7 Electric Motor Can be duplicated for classroom use 2 of 7 Electric Motor

Guiding the INVESTIGATION Guiding the INVESTIGATION

 Looking inside the electric motor  What is an electromagnet? Circulate among the groups, making sure that each Turning a motor using magnets is fun and helps student is an active participant in the investigation. students see how the motor works. But if the only If students have trouble making the disk spin, way to turn a motor was to stand there and flip suggest that they hold the magnet slightly above the magnets all day, it wouldn’t be a great invention. rotor magnets and push downward until the rotor With an electromagnet, the north and south poles magnet is repelled. Then they must quickly pull the can be switched with electricity. magnet backward as the rotor spins. Otherwise they may pull the next magnet right out of the motor. Electromagnets involve a connection between The secret is to keep reversing the magnet in their electricity and magnetism. They are a type of magnet fingers to push and pull each magnet in the rotor created when there is electric current flowing in a as it passes by. With a little practice, each student wire. Electromagnets are a temporary magnet, and should be able to spin the rotor. Another technique their magnetic field only exists when the electric is to stack two magnets together in your hand for a current is flowing. Their poles can be reversed, back stronger magnet. and forth between north and south, by reversing the direction of their current.

EM_TG.indb 18 40 7/17/14 11:56 AM A3

Explore INVESTIGATION A3 Explore INVESTIGATION A3

1. Take the magnets out of the rotor. Place the orange commutator disk on the rotor and gently secure it 3. Slide the electromagnet back in place toward the center of the rotor and gently tighten down the thumb- with the nut. The orange disk has three black spaces and three clear spaces around the edge. nuts to make electrical contact. 2. Place the electromagnet on the electric motor. Slide it toward the center of the rotor and gently tighten down the thumb-nuts to hold it in place and make electrical contact. 3. Connect the battery pack with the red wire in the red socket and the black wire in the black socket. 4. Hold down the RUN button and slowly rotate the rotor with your hand. a. What do you notice about the position of the north and south poles of the electromagnet as you spin the rotor? The poles of the electromagnet switch positions.

b. When is the north pole of the electromagnet closest to the rotor? When is the south pole of the electromagnet closest to the rotor? The north pole is closest to the rotor when a clear section is under the light beam switch. The south pole is closest to the rotor when a black section is under light beam switch. This happens independently of which way the rotor is turning. 4. Hold down the RUN button. The rotor will start spinning! You may need to give the rotor a little push at first. Now, you have a working electric motor!  Working with the electromagnet  Analyzing the motor’s motion 1. Now, take off the orange disk and put the six magnets back in place as shown below. You will need to loosen the thumbscrews on the electromagnet and slide it back before removing the disk. Now, you will analyze the motor’s motion. Hold down the RUN button and slowly turn the rotor by hand. Watch the green light on the electromagnet as the alternating black and clear sections of the rotor pass under it. 2. Replace the disk on the rotor like the picture shows. Make sure that the boundary lines between the black and clear sections are positioned at the centers of your six magnets. a. What do you notice? How do the poles of the electromagnet change compared to the poles of the permanent magnet in the rotor? The poles keep switching. When the south pole of a permanent magnet is close to the electromagnet, the north pole of the electromagnet is closest to the rotor. The opposite occurs when the north pole of a permanent magnet in the rotor is close to the electromagnet.

Copyright © CPO Science A3 How a Motor Works A3 How a Motor Works 3 of 7 Copyright © CPO Science Can be duplicated for classroom use Electric Motor Can be duplicated for classroom use 4 of 7 Electric Motor

SCIENCE AND LANGUAGE TEACHING TIP

Commutator – (from Latin mutare meaning “to If the electric motor doesn’t work properly, try the change altogether”) following troubleshooting procedures:

Commutator shares its origin with two other 1. Check the batteries. Is one of the green lights on words that should be familiar to students: when the RUN button is held down? Sometimes mutate and commute. Ask students to think the battery holders are tight and prevent the about what happens when something mutates. batteries from touching in the center. Rolling the Steer students toward using the word change to battery around usually works to fix this problem. describe mutations. Then ask, “What does it mean 2. Check that the electromagnet is not touching when someone commutes to and from work?” A the rotor. If it is, slide it back a little. commuter travels from home to work and then back 3. Check that the thumb nuts on the again home. “Commutator” combines meanings electromagnet are making a good connection from both of these words. The commutator changes to the circuit board. the direction of current altogether, like a commuter 4. Check that the commutator disk is lined up so travels to work and back again, or a mutation the edges from clear to black are aligned with changes something completely. the centers of the four magnets in the motor.

Electric Motor 19

EM_TG.indb 19 41 7/17/14 11:56 AM How a Motor Works

Explore INVESTIGATION A3 Explore INVESTIGATION A3

b. How do you think the electromagnet, the permanent magnets, and the disk work together to make the c. Look at the following pictures and determine where the north pole is when the disk is in each position. rotor spin? Write down your ideas as a short paragraph or as a series of steps. Circle the picture that shows the correct location of the north and south poles for each disk position. Be The poles of the electromagnet switch every time a black/clear sure to use the electric motor to see if your answer is correct. boundary passes the light beam on the electromagnet. The switch of the pole is such that the next permanent magnet in the rotor is attracted (or pulled) toward the electromagnet. The orientation of the magnets relative to the sections indicates whether the rotor will spin clockwise or counterclockwise. For example: (1) The clear section of the disk is under the beam and the north pole of the electromagnet is closest to the rotor; (2) This north pole is attracting the outward facing south pole of the next permanent magnet in the rotor; (3) The south pole of this permanent magnet reaches the beam of the electromagnet at the same time as the boundary from clear to black; (4) The poles of the electromagnet switch—now the south pole of the electromagnet is closest to the rotor; and (5) The permanent magnet under the beam is repelled and the next magnet in the rotor (with the north pole facing out) is attracted to the electromagnet.

When the black section is under the electromagnet, the south pole of the electromagnet is closest to the rotor. The permanent magnet nearest the electromagnet is being repelled and the next permanent magnet in the rotor (with the north pole facing out) is being attracted. When the clear section is under the electromagnet, the north pole is closest to the rotor. The permanent magnet nearest the electromagnet is being attracted.

Copyright © CPO Science A3 How a Motor Works A3 How a Motor Works 5 of 7 Copyright © CPO Science Can be duplicated for classroom use Electric Motor Can be duplicated for classroom use 6 of 7 Electric Motor

STEM CONNECTION

Hybrid Cars Electric motors are quiet, produce no emissions, and are able to generate powerful forces Conventional car Hybrid car very quickly. Despite these advantages, electric cars Gas tank Small high-efficiency have not been widely accepted in the marketplace. engine Their biggest drawback is battery weight: one kilogram of gasoline yields more than 30 times the energy Gas tank High-powered Electric stored in one kilogram of batteries. In order to store engine motor enough energy to be practical, electric cars are heavy Batteries and have a range of only 50 to 100 Conventionalmiles before the car Hybrid car batteries need to be recharged. Gas tank Small high-efficiency Hybrid cars combine the advantages of gasoline and engine electrical power. In the most promising hybrids on the market today, a small, efficient gasoline engine is combined with a battery-poweredGas tank electric motor.High-powered The Electric engine motor two power sources work together to achieve good Batteries performance and excellent fuel efficiency.

EM_TG.indb 20 42 7/17/14 11:56 AM A3

Explore INVESTIGATION A3 Evaluate INVESTIGATION A3

d. Suppose you have a rotor with magnets Name ______Date ______like the ones in the picture to the right. The electromagnet has a north pole facing 1. What is the difference between a permanent magnet and an electromagnet? in towards the rotor. Which way will it turn? Circle the correct direction. The north and south poles in a permanent magnet are fixed and It will spin clockwise. don’t change positions. The poles for an electromagnet are created when electricity is flowing. The orientation of the poles depends on

e. How can you make your motor spin the the direction that the current is flowing, so they can be easily other way? Explain your procedure. reversed. The motor will spin the 2. Electric motors are everywhere. List at least 5 things you own or use that contain electric motors. How other way if all of the permanent magnets many electric motors have you used today? (shown in the diagram) are flipped. For example, all the magnets Common objects that have motors are: cars, blenders, hair dryers, with the north pole facing out would be flipped to have the south food processors, and fans. Today, I have used two objects that have pole facing out, and all the magnets with the south pole facing out electric motors—a car and a fan. would be flipped to have the north pole facing out.

3. Would the motor at right spin? Why or why not? No, the setup would not spin because the permanent magnets all have their north poles facing outward. This setup would spin if the orientation of the magnets alternated.

4. Examine the two motor designs at right. Which one will spin faster? Explain your answer. Disk B will spin the fastest because there are more opportunities for the poles to switch. Each time the poles of the electromagnet are switched is an opportunity for the disk to be pulled around. In these terms, disk B gets “pulled” six times for each rotation, while disk A gets pulled two times.

STEM CONNECTION

(continued from previous page) hybrid model has an engine that weighs a mere Ordinary car engines are built with extra power 124 pounds yet produces 67 horsepower. capacity to provide rapid acceleration when passing or Hybrid cars do not need to be “plugged in” overnight starting. Cruising at constant speed requires less than to be recharged like pure electric cars. The gasoline 15 percent of a typical engine’s maximum power. Fuel engine includes an electric generator that continuously efficiency suffers because large engines are inefficient recharges the batteries while you are driving. at the low power levels used for 95 percent of driving. One of the most innovative developments in hybrid Conventional engine designs are a compromise technology is regenerative braking. Conventional between the high power needed for acceleration and braking systems dissipate a car’s kinetic energy the low power needed for normal driving. through friction, resulting in heat. In a hybrid car, In a hybrid car, the small, high-performance gasoline however, the electric motor also works as a generator. engine is used for normal driving. The electric Regenerative braking uses some of the car’s kinetic motor supplies extra power for fast starts and rapid energy to turn the motor into a generator that charges acceleration. The gas engine can be relatively powerful the batteries during slowing or stopping. This process while producing ultra-low levels of emissions. One recycles kinetic energy that would otherwise be lost.

Electric Motor 21

EM_A3_TG.indd 21 7/17/14 3:21 PM How a Motor Works

Notes and Reflections Evaluate INVESTIGATION A3

5. Magnetically levitated (also called “maglev”) trains use electromagnets to lift a train a few inches above the track and to pull it forward. Research maglev trains and find out where they are in use today. In an effort to reduce traffic, the U.S. government is supporting research on the development of the first maglev train for the country. Maglev trains are much faster than traditional rail systems because they travel on air, held off the track by a magnetic field. By “floating” the train on a powerful magnetic field, the friction between wheels and rails is eliminated. Maglev trains achieve high speeds using less power than a normal train. The first commercially operated maglev train is in China and runs between the city of Shanghai and the Pudong Airport. The train travels the 30 km (19 mile) distance in 7 minutes 20 seconds, reaching a speed of 431 km/h (268 mph).

WRAPPING UP

Have your students reflect on what they learned from the investigation by answering the following questions: 1. What are the important parts of an electric motor? 2. What is an electromagnet? 3. How can you control the direction that a motor spins?

EM_TG.indb 22 44 7/17/14 11:56 AM