Magnetism
Electronics
Lesson Plan
Performance Objective
Upon completion of this lesson, the student will be able to demonstrate an understanding of magnetism
concepts by correctly performing the procedures outlined on the lab activity sheets and by scoring 70 % on the
Basic Electronics – DC Magnetism Exam.
Specific Objectives
• Describe magnets and magnetism
• Define terms associated with magnetism
• Name two ways of producing artificial magnets
• Distinguish between high, medium, low, and non-permeable magnetic materials
• Select true statements concerning magnetic lines of force, magnetic fields, magnetic flux, and
flux density
• Discuss the use of the right- and left-hand rules for conductors and coils using an illustration
• Discuss the method and effect of induction
• List practical applications of induction in the electronics field
• Demonstrate the ability to
o Show the existence of magnetic lines of force around a magnet
o Demonstrate that magnetic poles can attract and repel
o Construct a simple electromagnet and check its operation
Terms
 Magnetism- a property of certain materials (e.g. iron, nickel, and cobalt) that exerts a mechanical force
on other magnetic materials, and can cause induced voltages in conductors when relative movement is
present
 Magnet- an object that will attract iron, nickel, or cobalt and will produce an external magnetic field
 Natural magnet- any material found in the earth that exhibits the properties of magnetism (example:
the lodestone, which contains magnetite[ a form of iron] and has been magnetized by the earth’s
magnetic field)
 Artificial magnet- a device that has been made magnetic by induction
 Magnetic Induction- where a magnetic field causes an un-magnetized ferromagnetic substance to
become magnetized
 Magnetic lines of force- a set of imaginary curved lines around a magnet that indicates the strength
and direction of the magnetic field
 Magnetic field- the area around a magnet through which the lines of force flow
 Permanent magnet- a magnetic device that retains its magnetism after it is removed from a magnetic
field
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Electromagnet- a core of soft iron that is temporarily magnetized by sending current through a coil of
wire wound around the core
Permeability- the ability to pass or conduct magnetic field lines (note: some materials, such as iron,
have high permeability, others such as aluminum have medium permeability, and others like silver and
gold have low permeability.)
Magnetic poles- one of the two ends of a magnet where magnetic field lines converge or diverge
(note: by convention, the north-seeking pole is marked with N, a plus, or is colored red.)
Ferromagnetic- magnetic materials with high values of permeability that range from 50 to 5000 (note:
steel, cobalt, nickel, and alnico are ferromagnetic materials.)
Diamagnetic- non-magnetic materials; these have a permeability of less than one (note: diamagnetic
materials include bismuth, antimony, copper, and zinc.)
Time
It should take approximately three 50-minute class periods to teach the lesson and one 50-minute class period
for the lab.
Preparation
TEKS Correlations
This lesson, as published, correlates to the following TEKS. Any changes/alterations to the activities may result
in the elimination of any or all of the TEKS listed.
Electronics
 130.368 (c)
o (3) The student develops skills for managing a project. The student is expected to:
(A) use time-management techniques to develop and maintain work schedules and
meet deadlines;
(B) complete work according to established criteria; and
(C) participate in the organization and operation of a real or simulated engineering
project.

130.368 (c)
o (5) The student implements the concepts and skills that form the technical knowledge of
electronics using project-based assessments. The student is expected to:
(B) demonstrate an understanding of magnetism and induction as they relate to
electronic circuits; and
(C) demonstrate knowledge of the fundamentals of electronics theory.

130.368 (c)
o (6) The student applies the concepts and skills to simulated and actual work situations. The
student is expected to:
(B) apply electronic theory to generators, electric motors, and transformers.
Interdisciplinary Correlations
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Physics
 112.39 (c)
o (5) Science concepts. The student knows the nature of forces in the physical world. The student
is expected to:
(D) identify examples of electric and magnetic forces in everyday life;
(E) characterize materials as conductors or insulators based on their electrical
properties;
(F) design, construct, and calculate in terms of current through, potential difference
across, resistance of, and power used by electric circuit elements connected in both
series and parallel combinations; and
(G) investigate and describe the relationship between electric and magnetic fields in
applications such as generators, motors, and transformers.
Occupational Correlation (O*Net – www.onetonline.org/)
Job Title: Magnetic Resonance Imaging Technologists
O*Net Number: 29-2035.00
Reported Job Titles: Lead Magnetic Resonance Imaging MRI Technologist, Lead Technologist/Manager,
Magnetic Resonance Imaging MRI Specialist, Magnetic Resonance Imaging MRI Supervisor, Magnetic
Resonance Imaging MRI Technologist, Senior Staff Technologist, Staff Magnetic Resonance Imaging MRI
Technologist, Staff Technologist
Tasks
 Conduct screening interviews of patients to identify contra-indications, such as ferrous objects,
pregnancy, prosthetic heart valves, cardiac pacemakers, or tattoos.
 Operate Magnetic Resonance Imaging (MRI) scanners.
 Select appropriate imaging techniques or coils to produce required images.
 Inspect images for quality, using magnetic resonance scanner equipment and laser camera.
 Take brief medical histories from patients.
 Position patients on cradle, attaching immobilization devices if needed, to ensure appropriate
placement for imaging.
 Explain magnetic resonance imaging (MRI) procedures to patients, patient representatives, or
family members.
 Inject intravenously contrast dyes, such as gadolinium contrast, in accordance with scope of practice.
 Provide headphones or earplugs to patients to improve comfort and reduce unpleasant noise.
 Create backup copies of images by transferring images from disk to storage media or workstation.
Soft Skills
 Active Listening
 Operation Monitoring
 Reading Comprehension
 Critical Thinking
 Service Orientation
 Monitoring
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Speaking
Judgment and Decision Making
Social Perceptiveness
Accommodations for Learning Differences
It is important that lessons accommodate the needs of every learner. These lessons may be modified to
accommodate your students with learning differences by referring to the files found on the Special
Populations page of this website.
Preparation
 Review the slide presentation and lesson document prior to each class.
 Review and become familiar with the terminology and the example problems used.
 Have materials and handouts ready prior to the start of the lesson.
 Have parts and equipment ready before lab.
References
• Buchla, D. & Floyd, T. (2005). The science of electronics DC/AC. (Chapter 4). Upper Saddle River, NJ:
Pearson Prentice Hall.
• Floyd, T. (1993). Principles of electric circuits: Electron flow version. New York, NY: Macmillan Publishing
Co.
• Robertson, L. (1980). Basic electronics I. Mid-American Vocational Curriculum Consortium, Inc.
• NASA website: http://www.nasa.gov/pdf/417438main_Magnetic_Math.pdf
Instructional Aids
1. Magnetism Basic Electronics slide presentation and notes
2. Magnetism Lab Activity Handout #1 - Show the existence of magnetic lines of force around a magnet
3. Magnetism Lab Activity Handout #2 - Demonstrate that magnetic poles can attract and repel
4. Magnetism Lab Activity Handout #3 - Construct a simple electromagnet and check its operation
5. Basic Electronics – DC Magnetism Exam
6. Basic Electronics – DC Magnetism Exam Key
Introduction
•
Say
o Magnets are an important part of the electronics industry, and we need to make sure we understand
how they work and the different places they are used. Magnets are a lot more useful than holding
papers on your refrigerator with your hand!
•
Ask
o Can anyone tell me some of the places where magnets are used in electronics?
•
Show
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4
o A motor (example: a portable drill)
•
Say
o Magnets are used in a lot of places, like the motor in this drill. Motors require magnetism to create the
forces that make them spin. Televisions use them, hard disk drives use them, speakers use them, and
even magnetic levitation (maglev) trains use them. Let’s review how they work.
Outline
MI
OUTLINE
I.
II.
Magnetism basics
A. We all know what a magnet does; describing
exactly what magnetism is can be harder.
B. The field is invisible and lines of force are only
a convenient way to describe the field.
C. Magnetism is a property of certain materials;
the most common example is iron.
D. Iron filings show magnetic field lines, but this is
really just an artifact of the way the iron filings
become magnets and attract each other, end
to end.
E. A magnetic field does have a direction and a
magnitude.
What creates magnetism?
A. Each electron is actually a tiny magnet due to
what is called a “magnetic dipole moment.”
B. The dipole moment comes from an
electron’s spin.
C. According to the Pauli Exclusion Principle, pairs
of electrons must have opposite spins.
D. The net magnetism of electrons that are
grouped in pairs is zero because the individual
moments cancel.
E. Only materials that allow un-paired electrons
(meaning electrons in different orbits) can
allow the magnetic moments to add and
create a measurable magnetic field.
F. There are a lot of ways to categorize magnets.
One way is to look at the difference between
permanent magnets and electromagnets.
NOTES TO TEACHER
Begin Basic Electronics
DC – Magnetism slide
presentation.
Slides 1-8
Slides 9-14
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MI
OUTLINE
NOTES TO TEACHER
III.
Important terms and units
A. Retentivity describes how long a magnet holds
its magnetism and how easy it is to become
magnetized.
B. Retentivity also relates to energy loss due to
hysteresis when changing magnetism (as in an
electromagnet).
C. Permeability is a measurement of how easy a
material conducts magnetic lines of flux.
D. To make a stronger magnet you would use a
core made of material with high permeability.
E. Ferromagnetism is a term used to describe
natural magnets, which are usually made of
iron.
F. Ferro is a Latin term for iron and is used for the
atomic symbol for iron.
Slides 15-18
IV.
Relationships between currents, forces, and fields
A. Magnetic fields are circular.
B. Electrical fields are straight lines.
C. There is an orthogonal (or perpendicular)
relationship between current directions, force
directions, and field line directions.
D. Electric and magnetic fields are also called
transverse waves, which also means they are
perpendicular.
E. Because of the way the directions are at right
angles to one another, we have to use rules to
tell us the relationships.
F. These rules are called the right- and left-hand
rules.
G. The Hall Effect is an example where the use of
the Left-hand rule has a practical application.
Slides 19-23
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MI
OUTLINE
NOTES TO TEACHER
V.
Uses of magnetism
A. One of the most important uses of magnetism
is in motors and generators.
B. These two devices combine both electricity
and magnetism.
C. Motors primarily use the interaction of two
magnetic fields to create physical forces to
produce torque.
D. Generators have a conductor moving through
a magnetic field to create induction.
E. An AC motor creates a rotating magnetic field
that the spinning rotor will try to follow.
Slides 24-28
VI.
Magnetic properties and applications
A. The last part has a variety of topics that cover
additional features and characteristics of
magnetism.
B. Artificial magnets are created by forcing the
magnetic moments of the electrons to align.
C. Different magnetic materials have different
permeability, creating different strength
magnets.
D. Non-magnetic materials are called
diamagnetic.
E. There are good problems and examples for
using mathematics involving magnetism on the
NASA website.
Slides 29-35
VII. Terms and definitions
A. The terms and definitions can be used as a
review of the material.
B. Having covered the material, these terms
should make a lot more sense to the students.
C. Terms and definitions make good test and quiz
questions.
Slides 36-37
VIII.
Lab activities
A. Can be either guided or independent practice
B. Lab Activity Handout #1
C. Lab Activity Handout #2
D. Lab Activity Handout #3
NASA website
http://www.nasa.gov/p
df/417438main_Magnet
ic_Math.pdf
Distribute Lab Activity
Handouts #1, #2, and
#3. Teacher will grade
handouts. Distribute
exam and grade.
Students are required
to make 70% on exam.
IX. Basic Electronics – DC Magnetism Exam
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Multiple Intelligences Guide
Existentialist
Interpersonal
Intrapersonal
Kinesthetic/
Bodily
Logical/
Mathematical
Musical/Rhythmic
Naturalist
Verbal/Linguistic
Visual/Spatial
Application
Guided Practice
The students will answer questions about concepts and terms.
Independent Practice
The students will create flashcards with terms and definitions. Students will complete the lab activity,
Magnetism Lab Activity Handout #1, #2, and #3.
Summary
Review
Students will quiz each other on terms and concepts using flash cards.
Evaluation
Informal Assessment
The teacher will ask questions and observe students during lab.
Formal Assessment
Students take the Basic Electronics – DC Magnetism Exam that is graded by the teacher.
Enrichment
Extension
The students can research advanced topics on magnetism and Maxwell’s laws.
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Name_____________________________________Class:____________________Date:___/___/___
Basic Electronics - DC Magnetism
Lab Activity Handout #1 - Show the existence of magnetic lines of force around a magnet.
I.
Equipment and Materials
A. One magnet
B. Compass
C. Flat piece of glass or clear Lucite (approximately 8” X 10”)
D. Shaker of iron filings
II.
Procedure
A. With a compass at least five yards away from the magnet, see that the needle points to
earth’s “north.”
B. Bring the compass to within four inches of one pole of the magnet and observe the change
in the compass needle indication.
C. Bring the compass to within four inches of the magnet’s other pole and observe the change
in the compass needle indication.
D. Place the magnet under the center of the flat piece of glass.
E. Using the sketch below, move the compass into the positions indicated by number.
F. Record the needle indication at each of the positions.
G. With the magnet still under the center of the flat piece of glass, sprinkle iron filings on top
of the glass.
H. Observe the lines of flux indicated by the iron filings.
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Name_____________________________________Class:____________________Date:___/___/___
I. Make a sketch of the pattern formed by the filings
Answer the following questions and hand in for a grade.
1. Does the compass indicate that there is a force surrounding your magnet?
2. Do the compass indications show the direction of the flux lines? Explain why your compass indicates
the flow.
3. Do the iron filings concentrate at the poles?
4. Why are the lines of flux spread out when not in the vicinity of the poles? Give two reasons.
5. Do the lines of flux cross each other?
6. Give at least three other characteristics of magnetic fields that are illustrated by the position of the
iron filings.
J. Return the materials to their storage area
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Lab Activity Handout #1 KEY
I.
Make a sketch of the pattern formed by the filings
The sketch should look like the picture on slide 5.
Answer the following questions and hand in for a grade.
1. Does the compass indicate that there is a force surrounding your magnet?
o Yes
2. Do the compass indications show the direction of the flux lines? Explain why your compass
indicates the flow.
o Yes,
o Because the compass needle is magnetized and it will orient in the direction of the
external magnetic field.
3. Do the iron filings concentrate at the poles?
o Yes,
o Because the magnetic field is stronger near the poles.
4. Why are the lines of flux spread out when not in the vicinity of the poles? Give two reasons.
o The magnetic field lines get further apart.
o The magnetic field lines get weaker.
5. Do the lines of flux cross each other?
o No,
o Magnetic field lines never cross.
6. Give at least three other characteristics of magnetic fields that are illustrated by the position of the
iron filings.
o Are continuous and form loops
o Pass through all materials, magnetic and non-magnetic
o Always enter or leave the magnetic material at right angles to the surface
J. Return the materials to their storage area
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Name_____________________________________Class:____________________Date:___/___/___
Basic Electronics – DC Magnetism
Lab Activity Handout #2 - Demonstrate that magnetic poles can attract and repel.
I.
Equipment and Materials
A. Two magnets
B. Piece of flat glass (approximately 8” X 10”)
C. Small piece of iron
D. Small piece of brass
E. Shaker of iron filings
II.
Procedure
A. Place one magnet on a smooth surface.
B. Bring the north pole of the other magnet close to the north pole of the first one.
C. Observe and record the action of the magnets.
D. Repeat steps A, B, and C, but bring the north pole of one magnet close to the south pole of the
other.
E. Observe and record the action of the magnets.
F. Place the magnets under the glass with unlike poles opposite, but not touching, each other.
G. Sprinkle iron filings over the glass, tap glass gently to define lines of force, and sketch the
resulting pattern.
H. Lift the glass and replace the iron filings into the shaker.
I. Place the magnets under the glass with like poles opposite, but not touching, each other.
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Name_____________________________________Class:____________________Date:___/___/___
J. Sprinkle iron filings over the glass, tap glass gently to define lines of force, and sketch the
resulting pattern.
K. Replace the filings into the shaker.
L. Place one magnet under the glass.
M. On one end of the glass, place the small piece of iron close to the pole of the magnet but not
directly over the pole.
N. On the other end of the glass, place the small piece of brass close to the other pole of the
magnet but not directly over the pole.
O. Sprinkle iron filings on the glass, brass, and iron pieces.
P. Sketch the resulting pattern.
Answer the following questions and turn in for a grade.
1. Explain the reactions of the magnets in steps A, B, C, and D.
2. Explain how the sketches of like poles and of unlike poles show that there are forces of repulsion and
attraction.
3. What happened to the lines of force as they passed through the small piece of iron?
4. What happened to the lines of force as they passed through the small piece of brass?
5. Do the lines of force also pass through the glass?
6. Explain your sketch made in step P.
7. Clean up and return all materials to their storage area
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Lab Activity Handout #2 KEY
J. Sprinkle iron filings over the glass, tap glass gently to define lines of force, and sketch the
resulting pattern.
The sketch should look like the picture on slide 6.
P. Sketch the resulting pattern.
The sketch should look like the picture on slide 6.
Answer the following questions and turn in for a grade.
1. Explain the reactions of the magnets in steps A, B, C, and D.
o Like poles repel, unlike poles attract.
2. Explain how the sketches of like poles and of unlike poles show that there are forces of repulsion and
attraction.
o Like poles repel, and the field lines curve away from each other; unlike poles attract, and the
field lines go from one magnet to the other.
3. What happened to the lines of force as they passed through the small piece of iron?
o Iron is a good conductor of magnetic field lines; the lines of flux will bend and distort to go
through the iron.
4. What happened to the lines of force as they passed through the small piece of brass?
o Brass is not a magnetic material or a good conductor of magnetic field lines, so there is no
effect.
5. Do the lines of force also pass through the glass?
o Yes
6. Explain your sketch made in step P.
o The filing line up according to the external magnetic field lines of force.
7. Clean up and return all materials to their storage area.
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Name_____________________________________Class:____________________Date:___/___/___
Basic Electronics – DC Magnetism
Lab Activity Handout #3 - Construct a simple electromagnet and check its operation.
I.
Equipment and Materials
A. 1 ½ - volt battery (CAUTION: Use no more than 1.5 volts!)
B. 4 feet hook-up wire (insulated)
C. ¼” iron bolt, 3” long
D. Compass
E. Paper clips
II.
Procedure
A. Start at one end of the hook-up wire and wrap all of the wire around the bolt, leaving
approximately eight inches on both ends so you can hook your coil to the battery.
B. Before connecting the coil to the battery, check to see that the iron bolt is not a magnet.
(note: Do this by bringing the compass within four inches of each end of the bolt and observe little or no
change in the compass needle.)
C. Connect the coil to the battery.
D. Bring the compass within four inches of the bolt ends and observe the needle indications for
north and south poles.
E. See if the bolt will pick up the paper clips.
(note: Try both ends of the bolt.)
F. Disconnect the coil from the battery.
G. Carefully remove the bolt trying to keep the coil in its same shape.
H. Reconnect the coil to the battery.
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Name_____________________________________Class:____________________Date:___/___/___
I. Check for polarity and magnetism with the compass by bringing it close to the coil ends.
J. See if the coil will attract a paper clip.
(note: Try both ends of the coil.)
K. Disconnect the battery.
Answer the following questions and hand in for a grade.
1. Explain why both ends of the electromagnet, with the bolt in position, will pick up the paper clips.
2. Why was the coil weaker without the bolt?
3. Explain why the polarity observed with the compass was the same
with or without the bolt.
L. Clean up and place all materials back in their storage area.
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Lab Activity Handout #3 KEY
I. Check for polarity and magnetism with the compass by bringing it close to the coil ends.
o The opposite ends of the coil have different magnetic poles, so each coil end will attract the
opposite end of the compass needle.
J. See if the coil will attract a paper clip.
o Yes, it will.
(note: Try both ends of the coil.)
K. Disconnect the battery.
Answer the following questions and hand in for a grade.
1. Explain why both ends of the electromagnet, with the bolt in position, will pick up the paper clips.
o The induced field in the paper clip mirrors the coil field and the paper clips can rotate to allow
opposite polarities to attract.
2. Why was the coil weaker without the bolt?
o The bolt is a good conductor of magnetic field lines, so the field gets stronger with the bolt.
3. Explain why the polarity observed with the compass was the same with or without the bolt.
o The bolt only affects the magnetic field strength, not the polarity.
L. Clean up and place all materials back in their storage area.
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Name_____________________________________Class:____________________Date:___/___/___
Basic Electronics – DC Magnetism Exam
Match the terms with their correct definitions.
1. Magnetism
A The portion of a magnet where the magnetic lines appear to
converge or diverge
2. Magnet
B A set of imaginary curved lines around a magnet that indicates the
strength and direction of the magnetic field
3. Magnetic poles
C A property of certain materials, which exerts a mechanical force on
other magnetic materials, and can cause induced voltages in
conductors when relative movement is present
4. Magnetic lines
D An object that will attract iron, nickel, or cobalt, and that
will produce an external magnetic field
Match the terms with their correct definitions.
5. Ferromagnetic
A A measure of the effectiveness of a material as a path for magnetic
lines of force as compared with the effectiveness of air
6. Induction
B Non-magnetic materials with a permeability of less than one
7. Permeability
C The process of magnetizing an object by bringing it into the magnetic
field of an electromagnet or permanent magnet
8. Diamagnetic
D Magnetic materials with high values of permeability that range
from 50 to 5000
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Name_____________________________________Class:____________________Date:___/___/___
Match the inductance abbreviations with their correct definitions.
9. Artificial magnet
A Any material found in the earth that exhibits the properties of
magnetism
10. Permanent magnet
B The area around a magnet through which the lines of force flow
11. Electromagnet
C A device that has been made magnetic by induction
12. Magnetic field
D A core of soft iron that is temporarily magnetized by sending current
through a coil of wire wound around the core
13. Natural magnet
E A magnetic device that retains its magnetism after it is removed
from a magnetic field
14. Which of the following items is not a high permeability material?
A Iron
B Steel
C Cobalt
D Aluminum
15. Which of the following items is not a low permeability material?
A Copper
B Zinc
C Cobalt
D Bismuth
16. Which of the following items is not a medium permeability material?
A Copper
B Aluminum
C Manganese
D Chromium
17. Which of the following items is a nonmagnetic material?
A Antimony
B Paper
C Alnico
D Iron
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Name_________________________________Class:__________Date:___/___/___
18. Which of the following items is a high permeability material?
A Antimony
B Aluminum
C Alnico
D Zinc
19. Select the true statement from the following concerning magnetic lines of force, magnetic fields, magnetic
flux, and flux density.
A The direction of flow is from south to north pole
B Parallel lines going in opposite directions repel each other
C Magnetic lines of forces exert tension along their lengths, tending to lengthen themselves
D The magnetic lines of force are continuous and form complete loops
20. In the figure above, the fingers point in the direction of
A Current flow
B The magnetic field
C The force on the conductor
D Magnetic induction
21. Select the true statement from the following concerning Right-hand rule of thumb for conductors in the
figure below
A The thumb points in the direction of the current
B The right hand holds the key to magnetism
C The thumb points in the direction of the force
D The magnetic lines of force are opposite the pointing
fingers
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Name_____________________________________Class:____________________Date:___/___/___
22. What creates magnetism?
A Electrical charge
B The right hand holds the key to magnetism
C Iron filings
D The dipole moment of an electron
23. Which of the following is not a practical application of induction in the electronics field?
A Transformers
B Radio tuners
C The magnetic memory
D Motors and generators
24. Which of the following are ways of producing artificial magnets?
A Soldering and fabrication
B Pounding and welding
C Stroking and electrical coil
D Wetting and wicking
25. Which of the following is considered to be a natural magnet?
A Lodestone
B Electromagnet
C Permanent magnet
D Artificial magnet
26. What is retentivity?
A The ability to pass or conduct magnetic field lines
B The degree which a material will become magnetized due to an external magnetic field
C How long a magnet retains its magnetism
D The strength of attraction of unlike poles
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Basic Electronics – DC Magnetism Exam Key
Match the terms with their correct definitions.
1. Magnetism
C
A The portion of a magnet where the magnetic lines appear to
converge or diverge
2. Magnet
D
B A set of imaginary curved lines around a magnet that indicates the
strength and direction of the magnetic field
3. Magnetic poles
A
C A property of certain materials, which exerts a mechanical force on
other magnetic materials, and that can cause induced voltages
in conductors when relative movement is present
4. Magnetic lines
B
D An object that will attract iron, nickel, or cobalt, and that
will produce an external magnetic field
Match the terms with their correct definitions.
5. Ferromagnetic
D
A A measure of the effectiveness of a material as a path for magnetic
lines of force as compared with the effectiveness of air
6. Induction
C
B Non-magnetic materials with a permeability of less than one
7. Permeability
A
C The process of magnetizing an object by bringing it into the magnetic
field of an electromagnet or permanent magnet
8. Diamagnetic
B
D Magnetic materials with high values of permeability that range
from 50 to 5000
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Match the inductance abbreviations with their correct definitions.
9. Artificial magnet
C
A Any material found in the earth that exhibits the properties of
magnetism
10. Permanent magnet
E
B The area around a magnet through which the lines of force flow
11. Electromagnet
D
C A device that has been made magnetic by induction
12. Magnetic field
B
D A core of soft iron that is temporarily magnetized by sending current
through a coil of wire wound around the core
13. Natural magnet
A
E A magnetic device that retains its magnetism after it is removed
from a magnetic field
14. Which of the following items is not a high permeability material?
A Iron
B Steel
C Cobalt
D Aluminum
15. Which of the following items is not a low permeability material?
A Copper
B Zinc
C Cobalt
D Bismuth
16. Which of the following items is not a medium permeability material?
A Copper
B Aluminum
C Manganese
D Chromium
17. Which of the following items is a nonmagnetic material?
A Antimony
B Paper
C Alnico
D Iron
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18. Which of the following items is a high permeability material?
A Antimony
B Aluminum
C Alnico
D Zinc
19. Select the true statement from the following concerning magnetic lines of force, magnetic fields, magnetic
flux, and flux density.
A The direction of flow is from south to north pole
B Parallel lines going in opposite directions repel each other
C Magnetic lines of forces exert tension along their lengths, tending to lengthen themselves
D The magnetic lines of force are continuous and form complete loops
20. In the figure above, the fingers point in the direction of
A Current flow
B The magnetic field
C The force on the conductor
D Magnetic induction
21. Select the true statement from the following concerning Right-hand Rule of thumb for conductors in the
figure below
A The thumb points in the direction of the current
B The right hand holds the key to magnetism
C The thumb points in the direction of the force
D The magnetic lines of force are opposite the pointing
fingers
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22. What creates magnetism?
A Electrical charge
B The right hand holds the key to magnetism
C Iron filings
D The dipole moment of an electron
23. Which of the following is not a practical application of induction in the electronics field?
A Transformers
B Radio tuners
C The magnetic memory
D Motors and generators
24. Which of the following are ways of producing artificial magnets?
A Soldering and fabrication
B Pounding and welding
C Stroking and electrical coil
D Wetting and wicking
25. Which of the following is considered to be a natural magnet?
A Lodestone
B Electromagnet
C Permanent magnet
D Artificial magnet
26. What is retentivity?
A The ability to pass or conduct magnetic field lines
B The degree which a material will become magnetized due to an external magnetic field
C How long a magnet retains its magnetism
D The strength of attraction of unlike poles
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