THE MAGIC OF MAGNETS
From
Electricity and Magnetism
A Unit of Study
Produced by
Colgren Communications
Written by
John Colgren
Distributed by...
800.323.9084 | FAX 847.328.6706 | www.unitedlearning.com
This video is the exclusive property of the copyright holder.
Copying, transmitting, or reproducing in any form, or by any
means, without prior written permission from the copyright holder is prohibited (Title 17, U.S. Code Sections 501 and 506).
© 2004 Colgren Communications
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . .1
Instructional Notes . . . . . . . . . . . . . . . . .1
Links to Curriculum Standards . . . . . . . . .2
Student Objectives . . . . . . . . . . . . . . . . .3
Assessment Tools . . . . . . . . . . . . . . . . . . .3
Unit Test . . . . . . . . . . . . . . . . . . . . . . . . .4
Teacher Preparation . . . . . . . . . . . . . . . . .4
Introducing the Program . . . . . . . . . . . . .4
View the Program . . . . . . . . . . . . . . . . . . .4
Discussion Questions . . . . . . . . . . . . . . . .4
Description of Blackline Masters . . . . . . .5
Enrichment Activities . . . . . . . . . . . . . . . .6
Answer Key . . . . . . . . . . . . . . . . . . . . . . . .7
Internet Resources . . . . . . . . . . . . . . . . .11
Script of Narration . . . . . . . . . . . . . . . . .11
This video is closed captioned.
The purchase of this program entitles the user to the right to
reproduce or duplicate, in whole or in part, this teacher’s guide
and the blackline master handouts that accompany it for the purpose of teaching in conjunction with this program, The Magic of
Magnets. This right is restricted only for use with this program.
Any reproduction or duplication in whole or in part of this
guide and the blackline master handouts for any purpose other
than for use with this program is prohibited.
CLASSROOM/LIBRARY
CLEARANCE NOTICE
This program is for instructional use. The cost of each
program includes public performance rights as long as
no admission charge is made. Public performance rights
are defined as viewing of a video in the course of face-toface teaching activities in a classroom, library, or similar
setting devoted to instruction.
Closed Circuit Rights are included as a part of the public
performance rights as long as closed-circuit transmission
is restricted to a single campus. For multiple locations,
call your United Learning representative.
Television/Cable/Satellite Rights are available. Call your
United Learning representative for details.
Duplication Rights are available if requested in large
quantities. Call your United Learning representative for
details.
Quantity Discounts are available for large purchases. Call
your United Learning representative for information and
pricing. Discounts, and some special services, are not
applicable outside the United States.
Your suggestions and recommendations are welcome.
Feel free at any time to call United Learning
at 1-800-323-9084.
THE MAGIC OF MAGNETS
from
Electricity and Magnetism A Unit of Study
Grade Levels: 5-8
Viewing Time: 15 minutes
INTRODUCTION
This live-action program is designed for use with the intermediate grade levels (5-8).
This program is about magnetism. Magnetism was probably
discovered by accident when a farmer, or herder, from ancient
Greece came across a natural magnet called magnetite.
Possibly his metal spear was attracted to this rock. This unusual effect was discovered in a part of Turkey called Magnesia, so
the Greeks called the rock magnetite. There are all kinds of
magnets and they are used in a wide variety of ways—from
holding messages on refrigerator doors to generating electrical
power at the local power station. This program explores magnets from their many uses to how certain metals can be made
into magnets.
INSTRUCTIONAL NOTES
Before presenting this lesson to your students, we suggest that
you preview the program and review this guide and the accompanying blackline master activities in order to familiarize yourself with their content.
As you review the materials presented in this guide, you may
find it necessary to make some changes, additions, or deletions
to meet the specific needs of your class. We encourage you to
do so, for only by tailoring this program to your class will they
obtain the maximum instructional benefits afforded by the
materials.
It is also suggested that the program presentation take place
before the entire group under your supervision. The lesson
activities grow out of the context of the program; therefore, the
presentation should be a common experience for all students.
1
LINKS TO CURRICULUM STANDARDS
This Unit of Study addresses the following National Science
Education Standards for grades 5-8:
Science as Inquiry
Content Standard A:
• Abilities necessary to do scientific inquiry
Plan and conduct simple investigations.
Employ simple equipment and tools to gather data.
Use data to construct a reasonable explanation.
Communicate investigations and explanations.
• Understanding about scientific inquiry
Physical Science
Content Standard B:
• Energy is a property of many substances and is associated
with heat, light, electricity, mechanical motion, sound, nuclei,
and the nature of a chemical. Energy is transferred in many
ways.
• Electrical circuits provide a means of transferring electrical
energy when heat, light, sound, and chemical changes are produced.
Science and Technology
Content Standard E:
• Abilities of technological design
• Understanding about science and technology
People have always had questions about their world.
Science is one way of answering questions and explaining
the natural world. People have always had problems and
invented tools and techniques to solve problems.
Scientists and engineers often work in teams.
Tools help scientists make better observations, measurements, and equipment for investigations.
History and Nature of Science
Content Standard G:
• Science as a human endeavor
Science and technology have been practiced for a long time.
Men and women have made a variety of contributions
throughout the history of science and technology.
2
Although men and women using scientific inquiry have
learned much about the objects, events, and phenomena in
nature, much more remains to be understood. Science will
never be finished. Many people choose science as a career
and devote their entire lives to studying it.
STUDENT OBJECTIVES
After viewing the program and participating in the lesson activities, the students should be able to do the following:
• Describe the differences between permanent and electromagnets.
• Describe how an electromagnet is made and operated.
• Describe ways a permanent magnet can be damaged.
• Define the terms attract and repel with regard to the way magnets affect each other.
• Identify the poles of a magnet as the most powerful parts of
the magnet.
• Describe uses of permanent and electromagnets.
ASSESSMENT TOOLS
This lesson provides you with three different assessment tools.
Together they make it possible to closely follow the progress of
your students and to judge their mastery of the subject matter.
The Pre-Test (Blackline Master 1) can be used to get some
idea of students' understanding of the topic before the program
is presented.
The Program Quiz and its accompanying answer sheet
(Blackline Master 2) can be used either as a way to introduce
the topic prior to showing the program or to judge student mastery once the program has been presented.
The Post-Test (Blackline Master 13) can be used as a final test
for the lesson.
3
UNIT TEST
An optional Unit Test has been provided with this lesson. It can
be used as a final test to gauge student comprehension of the
material presented in all five lessons of this Unit of Study.
Answers to the Unit Test are provided in the Answer Key of this
instructor’s guide.
TEACHER PREPARATION
View the program and review the accompanying activities.
Duplicate any blackline masters you wish to distribute. If you
plan to use the Program Quiz, which immediately follows the
program presentation, you may wish to have copies of the quiz
ready to distribute at the completion of the program. Also, plan
to pause the tape between questions if students require more
time.
INTRODUCING THE PROGRAM
Ask the students to help you list some uses of magnets. The list
should include things such as holding things on refrigerators,
novelty toys or desk displays, clasps for jewelry, and other common uses. However, magnets help our phones to work. In every
phone, there is a magnet that helps change the electrical signals
into sound waves. Magnets are a part of electric motors.
Magnets help guide the electron guns shooting electrons at our
television screens so that we can see our favorite shows.
Probably the most important job magnets have is in the production of electricity in the giant generators at power plants.
VIEW THE PROGRAM
Viewing time for this program is 15 minutes. The program quiz
that follows the presentation will take about three minutes when
you build in pauses for recording answers.
DISCUSSION QUESTIONS
You may wish to conduct a discussion after viewing the program based on the following:
1. Review with the class the procedures for turning an iron nail
4
into a magnet. Why do we have to stroke the nail repeatedly in
the same direction with a permanent magnet? (The atoms of the
iron nail need to be magnetically aligned). Why would dropping the nail or heating the nail cause the magnetism to be lost?
(Dropping the nail would cause the atoms to become jostled
and out of alignment. Heating the nail causes the atoms to
move faster and fall out of alignment).
2. What are some advantages of the maglev train?
Non-polluting; high speeds of 300 miles per hour; quiet,
smooth ride.
DESCRIPTION OF BLACKLINE MASTERS
This program contains 13 blackline masters that can be used to
reinforce ideas and information presented in the program.
• Blackline Master 1, Pre-Test, provides a way of finding out
how much students know about the material covered in this lesson before you present it. Students’ scores on the Pre-Test can
be compared with their scores on the final Post-Test (Blackline
Master 13).
• Blackline Master 2, Program Quiz, is to be used at the end
of the program. At the completion of the program, there is a
short quiz. The narrator will read the questions which are displayed on the screen. Students can use Blackline Master 2 to
record their answers. Answers to the questions are provided in
the Answer Key section of this instructor's guide.
• Blackline Master 3, Compass Construction, is an experiment designed to demonstrate how the early Chinese sailors
constructed a compass for navigating a ship at sea.
• Blackline Master 4, What Do Magnets Attract?, is an
experiment to test different objects and determine whether they
are attracted by a magnet or not.
• Blackline Master 5, Lines of Force, is an experiment for
observing the lines of force between two different magnets as
the like and opposite poles are brought closer to each other.
5
• Blackline Master 6, Cut Up, is an experiment to illustrate
what happens when a magnet is cut into pieces.
• Blackline Master 7, Don't Do It, is an experiment to demonstrate what happens when a magnet is dropped or heated.
Students will make magnets out of some small iron nails.
• Blackline Master 8, Magnetism from Electricity, demonstrates that electricity produces magnetism. This is similar to
the classic demonstration of 1820 by the Danish physicist, Hans
Oersted.
• Blackline Master 9, Electricity from Magnetism, is an
experiment that demonstrates the famous experiment by
Michael Faraday, which shows how a bar magnet moving in
and out of a coil of wire will create a flow of electrons.
• Blackline Master 10, Electromagnets, asks students to build
an electromagnet and then test it with paper clips. At the bottom of the page are some ideas for further investigation.
• Blackline Master 11, Maglev, is an experiment for constructing a maglev demonstration.
• Blackline Master 12, Maglev, Version 2, is another method
for illustrating magnetic levitation. This one is very cool
because if it is set up properly, you can spin the pencil and it
will almost magically hover in place for quite a while.
• Blackline Master 12, Post-Test, is an evaluation tool for this
unit.
ENRICHMENT ACTIVITIES
1. Have some interested students do more research into maglev
trains. So far, the countries of Germany and Japan have led the
way in this new technology. In the United States, there are a
few projects that are planned to begin in the next few years.
There is a test facility in Florida.
2. Have students write a paper that discusses the advantages of
a mass transit system that utilizes the technology of magnetic
6
levitation. Have them consider the advantages of high speed
and no pollution. Wouldn't such a system pay for itself within a
short period of time? Imagine all the people who would want
to ride on such a network simply because it is such a novelty.
ANSWER KEY
• Blackline Master 1, Pre-Test
I. Fill in the blank
1. electricity
2. poles
3. repel
4. attract
5. iron, nickel, or cobalt
II. Short Answer
1. To make an electromagnet, you need an iron nail, some wire,
and a dry cell. Wrap the wire around the nail, leaving a few
inches of wire at each end to connect to the dry cell. The more
wraps, the strong the magnetic force.
2. An electromagnet can be turned on and off. That means you
can control the magnetism of an electromagnet. You can't do
that with a permanent magnet.
3. Electromagnets are used in motors, doorbells, telephone
receivers, maglev trains, etc.
4. If the same poles of two magnets are facing each other, the
magnets will repel, or move away, from each other. Like poles
repel and unlike poles attract.
5. If one magnet is flipped around so that opposite poles are facing each other, then the magnets will attract. Unlike poles
attract.
• Blackline Master 2, Program Quiz
1. b
2. a
3. c
4. a
5. d
• Blackline Master 3, Compass Construction
Observations:
1. The cork and needle should spin around to be oriented with
the earth's magnetic poles.
7
2. The cork and needle should realign with the earth's magnetic poles.
Conclusions:
1. The needle has been magnetized, so it will now respond to
the earth's magnetic poles.
• Blackline Master 4, What Do Magnets Attract?
Answers will vary depending on the objects selected to be tested. However, only things made of iron, nickel, and cobalt will
be attracted to a magnet.
• Blackline Master 5, Lines of Force
• Blackline Master 6, Cut Up
Observations:
1. It should have become magnetic.
2. Yes
3. Yes
Conclusion:
A magnet can be cut into smaller pieces and still retain its magnetism.
• Blackline Master 7, Don't Do It
Observations:
1. Yes
2. No
3. No
Conclusion:
Dropping and heating will cause a magnet to lose its magnetism.
• Blackline Master 8, Magnetism from Electricity
Observations:
1. The compass needle will begin to spin.
2. The needle of the compass would stop spinning.
8
Conclusions:
1. It demonstrates that electricity causes a magnetized needle to
respond and spin. This means that the electricity is producing
a magnetic field in the coil of wire.
2. If more wire is used, there will be more of an effect.
• Blackline Master 9, Electricity from Magnetism
The compass needle will move as the magnetic bar is drawn in
and out of the coil of wire. If you watch closely, you will see
that the needle moves one way when the magnetic bar goes in
the coil and the needle moves the opposite way when the magnetic bar is moved out of the coil of wire. This is called alternating current.
• Blackline Master 10, Electromagnets
1. No
2. Yes
3. The magnetism stops and the paper clips fall.
Conclusions:
The electromagnet only works when electricity is flowing
through it. When the electricity is turned off, the electromagnet
loses its magnetic force.
• Blackline Master 11, Maglev
It bounces back up.
• Blackline Master 12, Maglev Version 2
When the pencil is given a spin, it will turn quickly as it hovers
over the magnets. There is very little friction in this set-up
because the only thing making contact is the pencil tip on the
smooth surface of glass. The pencil will spin for quite awhile.
• Blackline Master 13, Post-Test
Definitions:
1. Repel means to move away from or force away.
2. Attract means to come together or pull towards each other.
3. An electromagnet is a magnet that only works when electricity is flowing through it. Its magnetism can be controlled.
4. The poles of a magnet are the opposite ends of the magnet.
They are the most powerful parts of the magnet.
5. Magnetite is a natural stone that has magnetic properties.
9
II. Short answer
1. Wrap wire around an iron nail and then connect the ends of
the wire to a dry cell.
2. Electromagnets are used in motors, doorbells, telephones,
magnetic levitation trains, etc.
3. Electromagnets can be controlled. Their magnetism can be
turned on and off. Permanent magnets can't be turned on and
off.
4. A magnet spinning inside a coil of wire or a coil of wire spinning inside a magnetic field will cause electricity to flow.
5. Bring a compass near a wire that has electricity flowing
through it and the needle will move around.
• Unit Test
I. Matching
1. d
2. h
3. f
4. a
5. i
6. g
7. c
8. e
9. b
II. Short Answer
1. copper, silver, gold
2. wood, glass, rubber, cloth, plastic
3. Insulators are used to stop the flow of electricity. In-sulators
around a wire will stop the electricity from moving out of the
wire and into another conductor.
4. A generator produces electricity. It is made of either a coil of
wire spinning in a magnetic field or a magnet spinning in a coil
of wire. In either case, a flow of electrons is created.
5. An electromagnet can be made with a source of electrons,
some wire, and an iron nail. Wrap the wire around the nail.
Connect the wire ends to the terminals of the battery and you
have an electromagnet.
6. An electromagnet can be turned on and off, but a regular bar
magnet can't.
7. A source of electrons, a path for the electrons to flow along,
and something to use the electrons.
8.
battery
battery
10
9. A series circuit has one path on which electricity flows. If a
bulb in a series circuit burns out, all the lights go out. A parallel circuit has two paths on which the electricity flows. If one
bulb burns out, there is still a path for the electricity to flow
along so other bulbs in the circuit stay lit.
10. Fuses and circuit breakers will automatically trip, or stop,
the flow of electricity if the circuit becomes overloaded by the
flow of current.
11. Answers will vary.
12. The sun's energy through the use of solar cells, wind turbines, geothermal energy, chemical energy.
13. They would move apart because they would be repelled.
14. They would come together because they are attracted.
15. a. 4 amps
b. 8 amps
c. 6 amps
INTERNET RESOURCES
The following websites may be valuable sources of additional
information to reinforce the objectives of this lesson:
1. http://www.school-for champions.com/science/magnetism.htm
2. Canada Science and Technology Museum
http://www.sciencetech.technomuses.ca/english/schoolzone/Info
_magnets.cfm
SCRIPT OF NARRATION
Look. Nails hanging from a rock.
Paperclips picked up by a piece of rock. What’s going on here?
Well, you are seeing a natural occurring magnet called magnetite or a lodestone in action. These rocks have the ability to
attract certain objects with an invisible force called magnetism.
It is thought that possibly two thousand years ago some ancient
Greeks discovered by accident the ability of certain rocks to
attract some metals. Maybe a farmer had a metal tool or spear
head magically stick to a piece of magnetite.
11
They discovered this unusual effect in a part of Turkey called
Magnesia, so the Greeks called the rock responsible for this
attractive force magnetite.
Today we have permanent magnets that are used in hundreds of
ways, from holding pictures on the refrigerator to producing
electricity inside huge generators.
It’s fun to mess around with magnets. They come in all kinds
of sizes, shapes, and strengths. Some magnets are round, some
are bar-shaped, some are shaped like horseshoes, and some are
donut shaped.
Magnets have two poles: a north and a south pole. Sometimes
the magnet is colored to distinguish from north and south.
These donut magnets are an excellent way to show how magnets attract and repel. When opposite sides of the magnets are
facing each other, the magnets are attracted and come together.
If the similar sides are facing each other, then the magnets
repel, or push away, from each other.
We can illustrate this with bar magnets as well. When the same
sides are brought near, they push apart. However, when opposite sides are near, they attract or pull together.
Magnets don’t attract all objects. You can experiment with various objects to see what is attracted and what isn’t attracted to
a magnet. It might appear that objects made of metals are all
attracted but that isn’t necessarily true. Only certain metals are
attracted by magnets.
These coins are made of metal but are not attracted to the magnet. But this paper clip and these staples are definitely attracted
to the magnet.
You’ll find that only metals made of nickel, iron, and cobalt are
attracted by magnets.
Magnetism can penetrate objects as demonstrated by this magnet moving the paper clip through the wood.
12
If we put a bar magnet into a bowl of paperclips, we will find
that most of the clips attach to the ends of the magnet. The
magnets are strongest at the ends.
We can see the lines of force around a magnet by placing a
piece of glass or thin cardboard on top of the magnet. Then we
sprinkle iron fillings onto the glass or cardboard and the little
bits of iron line up along the invisible lines of force that are
found around the magnet. We can view the lines of force created when the ends of two different magnets are brought near
each other. Remember that unlike ends of magnets attract each
other and like ends repel. Let’s look at the lines of force when
unlike sides of two magnets are brought near. Now let’s turn
one magnet around so that like ends are facing each other. You
can see the lines of force are repelling each other.
If we tie a string to a bar magnet and let it hang, it will rotate
around until one end is pointing north and the other end is
pointing south.
The end of the magnet that points north is called the magnet’s
north pole and the opposite end is called the south pole. The
magnet lines up this way because the earth is a giant magnet.
It is as if a giant bar magnet went through the center of the
earth, as shown in this picture. The magnet isn’t really there.
In fact, scientists believe that the magnetic effect is caused by
very hot liquid metals in the outer core of the earth, creating
electrical charges that cause a magnetic field to develop. The
invisible magnetic field extends out into space, protecting the
earth against solar particles released constantly by the sun. This
stream of particles is called the solar wind. These charged particles make contact with the earth’s magnetic field lines and
travel towards the poles. As the particles make contact with
oxygen and nitrogen atoms in the atmosphere, a beautiful show
of lights in the sky is displayed. These are referred to as auroras or the northern and southern lights.
The ancient Chinese were the first navigators to use magnets to
help them sail the seas. They found that they could use natural
magnets held by string as a method for identifying north and
13
south. These were the first compasses. Later, it was discovered
that a needle, or thin piece of iron, could be turned into a magnet by stroking the magnetite across it repeatedly. This needle
suspended on a piece of bamboo, or cork, and floating in water
would rotate around until one end pointed north. Sailors could
then determine what direction they were sailing in by comparing this needle with the direction of the boat.
WHAT MAKES CERTAIN MATERIALS MAGNETIC?
All matter is made up of atoms. Inside atoms are orbiting electrons that speed around the atom’s center, or nucleus. The
movement of electrons causes a magnetic effect and atoms
develop a north and south pole.
In most materials, the magnetic fields cancel each other out, so
these materials have no magnetism. However, the atoms of
iron, nickel, and cobalt are different. They have domains, or
groups of atoms, that line up together creating a magnetic field.
Objects made of iron, nickel, or cobalt can be magnetized by
stroking them with a magnet.
You must stroke them in the same direction to get the atoms to
align properly. A magnet made this way is called a temporary
magnet. This iron nail is turned into a temporary magnet after
repeatedly rubbing a permanent magnet along its length. It
attracts the staples because the magnetic force in the nail causes the atoms of the staples to slightly line up with the nail’s
magnetic field. This creates a temporary magnetic effect in the
staples and they are attracted to the nail. When the staples are
knocked free, they loose that magnetic effect.
Magnets can be damaged and loose their magnetic ability if
they are dropped or heated. Dropping causes the domains in the
atoms to be jumbled around. They fall out of alignment and the
magnetic effect is lost. Heating can also damage a magnet.
When atoms are heated, they move faster and, as a result, move
out of alignment.
ELECTROMAGNETS
In 1820, the Danish physicist Hans Oersted discovered that
electricity could cause a magnetic effect. During a demonstra14
tion he brought a compass near a wire that had an electric current flowing through it. The needle spun in a new direction. He
found this to be very unusual, as compass needles always pointed north and south. With further experimentation, he found that
electricity flowing through a wire created a magnetic effect.
An electromagnet can be made with some simple materials. An
iron nail, some wire, and a battery can be used to make an electromagnet. Wind the wire around the nail. Attach the ends of
the wire to the battery and the electricity flowing through the
wire creates a magnetic field around the wire and nail. The
domains of the atoms in the nail are temporarily lined up to
form a temporary magnet. When one of the ends of the wire is
disconnected, the flow of electrons stops and the magnetism
stops.
Electromagnets are used in various ways. Doorbells use electromagnets. Notice the coiled wires and the way they attract the
doorbell clapper when the electricity is applied.
There are electromagnets in a phone receiver that change the
electric signals into sound waves.
There are electromagnets in many motors. This motor has magnets with a driveshaft between them that contains the electromagnets.
Here is an experiment conducted at the Museum of Science in
Boston to illustrate the power of an electromagnet. The power
drill has been set up with a handle, or crank, in its bit. The batteries are removed and instead, wires are attached from the drill
motor to a light bulb and to the coil of wire of an electromagnet. Using the crank, the electric motor becomes a generator as
demonstrated by the light bulb.
You could run a series of experiments to test what factors effect
the strength of the electromagnet. Does the size of the iron core
effect the strength? How about the number of turns of wire? Or
maybe the strength, or voltage, of the battery used will determine the strength of the electromagnet. Set up an experiment to
test all these variables one at a time.
15
ELECTRICITY FROM MAGNETISM
After Hans Oersted discovered that electricity created a magnetic effect, other scientists wondered if magnetism could create electricity.
In 1831, Michael Faraday, an English scientist, set up an experiment that proved that electricity could be produced when a
magnet was pushed in and out of a coil of wire.
Notice that the needle, which illustrates the flow of electricity,
only moves when the magnet first moves. Also, notice that the
needle changes direction as the magnet moves in different
directions in and out of the coil of wire. Electricity produced in
this fashion by a changing magnetic field is called electromagnetic induction. Faraday found that a greater electric current is
induced if there are more coils of wire. He also found that if the
magnet moves faster, the induced electric current is stronger.
Faraday also discovered that it didn’t matter if the magnet was
moved inside a coil of wire, or a coil of wire moved inside a
magnetic field. In either situation, electric current is induced.
At power plants, they use electromagnetic induction to produce
electric current. In most large generators, a giant magnet is
turned inside a coil of wire. Remember that the current electricity produced in this fashion changes direction continuously.
This is called ac or alternating current.
A battery produces dc or direct current. Direct current flows
steadily in one direction.
MAGLEV
This train is traveling 355 kilometers per hour, or 220 miles per
hour. That speed might seem impossible for a train but that
isn’t the most exciting thing about this train. You see this train
is traveling because of electricity and magnetism. This is a
maglev train. Maglev stands for magnetic levitation. As you
know, opposite ends of a magnet attract and similar sides repel.
This train is making use of these facts to race down the track.
This is the German magnetic levitation train called “transrapid.” It is designed to go as fast as 550 kilometers per hour,
which is 342 miles per hour. There are magnetized coils run16
ning along the track, or guideway. On the underside of the train
are large magnets. When electricity flows into the guideway
coils, a magnetic field develops. The opposing magnetic fields
of the guideway and train lift, or levitate, the train about one
centimeter, or about one third of an inch, above the track. Once
levitated, the electromagnet coils in the guideway are used to
push and pull the train along on a cushion of air. Because the
train is floating, there is no friction between the train and track,
which allows the train to reach unbelievable ground transportation speeds. This form of transportation has been in development since the 1970s.
Look at this maglev demonstration model. The device is easily suspended in mid air because inside are two donut magnets
that are repelled by magnets in the base. With a little twist, the
device spins effortlessly. There is only one place where contact
is made, so the friction is minimal. That’s why the device spins
for such a long time. With little friction between the moving
parts, the device can continue to spin for long periods of time.
Now it is time for the program quiz. There are five multiple
choice questions.
1. If two magnets have opposite poles facing each other, they
will be ________.
a. repelled
b. attracted
c. neutralized
d. opposed
2. If two magnets have the same poles facing each other, they
will be _________ .
a. repelled
b. attracted
c. neutralized
d. opposed
3. ___________ are controlled by electricity.
a. lodestones
b. pieces pf magnetite
c. electromagnets
d. permanent magnets
17
4. Iron nails can be made into magnets because of their
___________.
a. domains
b. lodestones
c. magnetite
d. protons
5. Mangets are used in electric motors and __________ .
a. horseshoes
b. lodestones
c. turbines
d. generators
18
19
20