People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular
Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged. See all articles from
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
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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.
||1 - The north pole of a compass
points to the earth's north magnetic pole.
2 - If the separation
between two unlike magnetic poles is reduced by half, the
attraction between them will become four times as great.
3 - If a compass is placed beneath a wire
passing electrons from A to B, its north pole will point
to the right.
4 - Bar magnets should be stored
by placing them so that like poles are side by side.
5 - There is no insulator for
magnetic fields. Some metals simply offer more resistance
to magnetism than others.
||6 - A "D-ring" is usually found
on d.c. electromagnetic relay coils.
7 - When a nickel-iron
rod is magnetized, it will grow shorter in length.
8 - The electromagnet shown here
will have its north pole located at the top of the coil.
9 - An electron passing through
the deflection yoke magnetic field and out of the page will
be deflected to the right.
10 - A "keeper" is placed across
the poles of a horseshoe magnet to prevent the magnet's
field from passing through nearby ferrous objects.
Here are other Popular Electronics quizzes:
- Lamp Brightness Quiz, January
- Graph Interpretation
Quiz, April 1967
Quizoo, October 1962
Electronic Photo Album Quiz, Mar 1963
Electronic Analogy Quiz, Nov
- Electronic Alphabet Quiz,
- RC Circuit Quiz, Jun 1963
- Diode Quiz, Jul 1961
Kool-Keeping Kwiz, Jun 1970
- Electronic Curves Quiz, Feb
- Electronic Numbers
Quiz, Dec 1962
Conversion Quiz, Apr 1963
Coil Function Quiz, Jun 1962
- Electronics Analogy Quiz, Aug
- Audio Quiz, April 1955
- Electronic Unit Quiz, May
- Capacitor Circuit Quiz, Jun
- Magnetic Phenomena
Quiz, Feb 1962
Electronics Geography Quiz, Apr 1970
Electronic Menu Quiz, Aug
- Electronic Noise Quiz, Aug
- Electronic Current
Quiz, Oct 1963
Electronic Inventors Quiz, Nov
- Resistor Function Quiz, Jan
- Electronic Measurement
Quiz, Jan 1963
- Vacuum Tube
Quiz, Feb 1961
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
7 TRUE. This is the principle of "magnetostriction"
used in ultrasonic transducers for sonar and in ultrasonic cleaning
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.
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