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Table
of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
from
Popular Electronics,
published October 1954 - April 1985. All copyrights are hereby acknowledged.
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If
terms like 'magnetostriction,' mu-metal,' and 'D-ring' arouse your
technostimulus receptors, then this quiz on magnetics should be
just what you've been waiting for. It appeared in a 1962 edition
of Popular electronics, but the principles therein have not changed
since then. I must admit that I had never given thought to the orientation
in which bar magnets should be stored when in close proximity to
each other.
See all articles from
Popular Electronics.
Magnetic Phenomena Quiz
By Robert P. Balin
Neither magnets nor magnetism are mysteries
to the experimenter. But this quiz will test your knowledge of the
basic principles of magnetic phenomena. Mark each statement "True"
or "False" and check your answers at the bottom.
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1 - The north pole of a compass
points to the earth's north magnetic pole.
TRUE
FALSE
2 - If the separation
between two unlike magnetic poles is reduced by half, the
attraction between them will become four times as great.
TRUE FALSE
3 - If a compass is placed beneath a wire
passing electrons from A to B, its north pole will point
to the right.
TRUE
FALSE
4 - Bar magnets should be stored
by placing them so that like poles are side by side.
TRUE FALSE
5 - There is no insulator for
magnetic fields. Some metals simply offer more resistance
to magnetism than others. TRUE
FALSE
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6 - A "D-ring" is usually found
on d.c. electromagnetic relay coils.
TRUE
FALSE
7 - When a nickel-iron
rod is magnetized, it will grow shorter in length.
TRUE FALSE
8 - The electromagnet shown here
will have its north pole located at the top of the coil.
TRUE FALSE
9 - An electron passing through
the deflection yoke magnetic field and out of the page will
be deflected to the right.
TRUE
FALSE
10 - A "keeper" is placed across
the poles of a horseshoe magnet to prevent the magnet's
field from passing through nearby ferrous objects.
TRUE FALSE
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Popular Electronics published many quizzes over the years
- some really simple and others not so simple. Robert Balin created many of the quizzes.
This is a listing of all I have posted thus far.
- TV Trouble Quiz,
July 1966
- Electronics History Quiz,
December 1965
- Scope-Trace Quiz,
March 1965 Popular Electronics
- Electronic
Circuit Analogy Quiz, April 1973
- Test
Your Knowledge of Semiconductors, August 1972
- Ganged Switching
Quiz, April 1972
- Lamp Brightness
Quiz, January 1969
- Lissajous Pattern Quiz, September 1963
- Electronic
Quizoo, October 1962
- Electronic Photo Album Quiz, March 1963
- Electronic Alphabet Quiz, May 1963
- Quiz: Resistive?
Inductive? or Capacitive?, October 1960
- Vector-Circuit Matching Quiz, June 1970
- Inductance
Quiz, September 1961
- RC Circuit
Quiz, June 1963
- Diode Quiz,
July 1961
- Electronic Curves Quiz, February 1963
- Electronic Numbers Quiz, December 1962
- Energy Conversion Quiz, April 1963
- Coil
Function Quiz, June 1962
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-
Series Circuit Quiz,
May 1966
-
Electrochemistry Quiz, March 1966
- Electronic Analogy
Quiz, November 1961
- Electronic
Coupling Quiz, August 1973
- Electronics Analogy Quiz, August 1960
- Audio Quiz,
April 1955
- Electronic
Unit Quiz, May 1962
-
Capacitor Circuit Quiz, June 1968
- Quiz on AC Circuit Theory, December 1970
- Magnetic Phenomena Quiz, February 1962
- Electronics Geography Quiz, April 1970
-
Electronic Menu Quiz, August 1963
- Electronic Noise Quiz, August 1962
- Electronic Current Quiz, October 1963
- Electronic Inventors Quiz, November 1963
- Resistor
Function Quiz, January 1962
- Electronic Measurement Quiz, January 1963
- Vacuum
Tube Quiz, February 1961
- Kool-Keeping Kwiz, June
1970
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Magnetic
Quiz Answers
1 TRUE. The north pole of a compass
points to the earth's north magnetic pole which is actually the
south pole of a large magnet inside the earth.
2 TRUE. The
force of attraction between unlike magnetic poles varies inversely
as the square of the distance between them.
3 TRUE. The
north pole of a compass always indicates the direction of the magnetic
field in which it lies. To determine the direction of the magnetic
field, grasp the wire with your left hand with the thumb in the
direction of electron flow, from A to B. Your fingertips will point
in the direction of the magnetic field.
4 FALSE. Bar magnets
should be stored so that opposite poles lie adjacent to each other.
The magnetic field from each bar will then have a closed magnetic
circuit lying entirely within the bars themselves. Hence, the magnetic
fields are least likely to go into nearby metallic objects.
5 TRUE. There are no materials which resist magnetic fields.
However, magnetic shields made of high-permeability materials such
as mu-metal are used to bypass magnetic fields around the devices
to be isolated from the effects of the magnetic fields.
6 FALSE. The D-ring is a shorted turn of copper used on a.c. relay
coils to prevent armature chattering. When the magnetic field set
up by the coil starts to collapse on alternate half cycles, a circulating
current in the D-ring builds up a magnetic field which holds the
contacts closed.
7 TRUE. This is the principle of "magnetostriction"
used in ultrasonic transducers for sonar and in ultrasonic cleaning
devices.
8 TRUE. Electrons will enter the coil from the
bottom and exit at the top of the coil. Grasp the coil with your
left hand with the fingers wrapped in the direction of the electron
flow. Your thumb will point to the north pole.
9 FALSE.
Use your left hand to determine the magnetic field around a moving
electron. The thumb points in the direction of electron flow and
the curled fingers point in the direction of its magnetic field.
Hence, the electron coming out of the page will have a clockwise
field around it. The magnetic field to the right of the electron
will have the same direction as the field of the deflection coil.
Since magnetic lines which have the same direction repel each other,
the electron experiences a force to the left.
10 TRUE. Almost
all of the magnet's magnetic lines of force will pass through the
soft iron bar. The "keeper" is usually employed when storing permanent
magnets in order to preserve the magnetic strength.
Posted June 12, 2013
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