September 1961 Popular Electronics
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Have you ever heard
of a "swinging choke?" I surely hadn't, so my probability of getting Inductance
Quiz, which appeared in a 1961 issue of Popular Electronics magazine, question
number 5 correct was 50% at best. I guessed wrong - just my luck. As a result my
score was 8/9 = 89%. Oh, the shame. Maybe you will have a better time of it. Be
careful with Q6 as well. Otherwise, if you understand the fundamentals of inductor
circuit analysis, you will have no problem. Bonne chance.
Inductance, as you may know, is the electrical property frequently compared to mechanical
inertia. To gauge your "inductance" knowledge, solve the problems below, then check
By Robert P. Balin
1 - The larger the resistance, the
greater the voltage developed on opening the switch.
3 - Increasing the supply frequency
will cause the lamp to glow more brightly.
5 - The inductance of a "swinging"
choke decreases as the current through it increases.
7 - The lamp will glow more brightly
as the iron core is moved out of the coil.
9 - The tuning slug on an oscillator
coil is most withdrawn at the top end of the band.
2 - Current will continue to flow,
even after the supply voltage has dropped to zero.
4 - Bunching a number of turns together
in a coil will increase its inductance.
6 - Inserting a brass-tipped tuning
wand into a coil will increase its inductance.
8 - Since a bifilar winding is "doubled
back" on itself, it boosts inductance.
See answers below.
Quizzes from vintage electronics magazines such as Popular
Electronics, Electronics-World, QST, and Radio News were published
over the years - some really simple and others not so simple. Robert P. Balin
created most of the quizzes for Popular Electronics. This is a listing
of all I have posted thus far.
Sawtooth Sticklers Quiz - November 1960 Radio-Electronics
Radio Quiz - December 1947 Radio-Craft
Quiz - October 1955 Radio & Television News
- Electronics Physics
Quiz - March 1974 Popular Electronics
- A Baffling Quiz
- January 1968 Popular Electronics
- Electronics IQ
Quiz - May 1967 Popular Electronics
- Plug and Jack
Quiz - December 1967 Popular Electronics
Switching Quiz - October 1967 Popular Electronics
Angle Quiz - September 1967 Popular Electronics
Electronics Quiz - July 1967 Popular Electronics
- FM Radio
Quiz - April 1950 Radio & Television News
- Bridge Circuit
Quiz -December 1966 Popular Electronics
- Diode Function
Quiz - August 1965 Popular Electronics
- Diagram Quiz,
August 1966 Popular Electronics
- Quist Quiz - November
- TV Trouble Quiz,
July 1966 Popular Electronics
- Electronics History Quiz,
December 1965 Popular Electronics
- Scope-Trace Quiz,
March 1965 Popular Electronics
Circuit Analogy Quiz, April 1973
Test Your Knowledge of Semiconductors, August 1972 Popular Electronics
- Ganged Switching
Quiz, April 1972 Popular Electronics
- Lamp Brightness
Quiz, January 1969 Popular Electronics
- Lissajous Pattern Quiz, September 1963 Popular Electronics
Quizoo, October 1962 Popular Electronics
- Electronic Photo Album Quiz, March 1963 Popular Electronics
- Electronic Alphabet Quiz, May 1963 Popular Electronics
- Quiz: Resistive?
Inductive? or Capacitive?, October 1960 Popular Electronics
- Vector-Circuit Matching Quiz, June 1970 Popular Electronics
Quiz, September 1961 Popular Electronics
- RC Circuit Quiz,
June 1963 Popular Electronics
- Diode Quiz, July
1961 Popular Electronics
- Electronic Curves Quiz, February 1963 Popular Electronics
- Electronic Numbers Quiz, December 1962 Popular Electronics
- Energy Conversion Quiz, April 1963 Popular Electronics
- Coil Function
Quiz, June 1962 Popular Electronics
Co-Inventors Quiz - January 1965 Electronics World
"-Tron" Teasers Quiz - October 1963 Electronics World
- Polarity Quiz
- March 1968 Popular Electronics
I.Q. Quiz - October 1948 Radio & Television News
- Amplifier Quiz
Part I - February 1964 Popular Electronics
Quiz - February 1967 Popular Electronics
Frequency Quiz - September 1965 Popular Electronics
Metals Quiz - October 1964 Popular Electronics
Measurement Quiz - August 1967 Popular Electronics
Quiz, June 1966 Popular Electronics
Geometry Quiz, January 1965 Popular Electronics
Factor Quiz, November 1966 Popular Electronics
Math Quiz, November 1965 Popular Electronics
- Series Circuit
Quiz, May 1966 Popular Electronics
Quiz, March 1966 Popular Electronics
Quiz: Test Your Sales Ability - April 1947 Radio News
Analogy Quiz, November 1961 Popular Electronics
Coupling Quiz, August 1973 Popular Electronics
- Electronics Analogy Quiz, August 1960 Popular Electronics
- Audio Quiz, April
1955 Popular Electronics
- Electronic Unit
Quiz, May 1962 Popular Electronics
Circuit Quiz, June 1968 Popular Electronics
- Quiz on AC Circuit Theory, December 1970 Popular Electronics
- Magnetic Phenomena Quiz, February 1962 Popular Electronics
- Electronics Geography Quiz, April 1970 Popular Electronics
Menu Quiz, August 1963 Popular Electronics
- Electronic Noise Quiz, August 1962 Popular Electronics
- Electronic Current Quiz, October 1963 Popular Electronics
- Electronic Inventors Quiz, November 1963 Popular Electronics
- Resistor Function
Quiz, January 1962 Popular Electronics
- Electronic Measurement Quiz, January 1963 Popular Electronics
- Vacuum Tube Quiz,
February 1961 Popular Electronics
- Kool-Keeping Kwiz, June
1970 Popular Electronics
- Find the Brightest
Bulb Quiz, April 1960 Popular Electronics
Where Do the Scientists Belong? - Feb 19, 1949 Saturday Evening
1 - True. When the switch is opened, the inductance of the coil
tends to maintain the same value of current flow in the circuit. And the higher
the value of the series resistance, the greater the e.m.f. which will be developed.
2 - True. Since current lags voltage by 90 degrees in a purely
inductive circuit, current will continue to flow after the voltage has dropped to
3 - False. Because of the back e.m.f. induced in the coil as
the current through it changes, the greater the rate of current change, the greater
is the opposition to such change. Thus, the higher the frequency of the current
through the coil, the greater the inductance, and the smaller the voltage delivered
to the lamp.
4 - True. Closely spacing a number of turns in a coil will increase
the strength of its magnetic field and thus its inductance.
5 - True. A swinging choke is an inductor which is designed
to reach a maximum amount of magnetization or "saturation" at low values of rated
current. From this point on, an increase in the amount of current reduces the degree
of magnetization and hence the inductance. A greater portion of the source voltage
therefore becomes available to compensate for the larger resistive voltage drops
occurring within the power supply.
6 - False. Eddy currents induced in the brass will produce a
magnetic field which opposes that of the coil and thus effectively reduces the coil's
7 - True. The iron core serves to increase the coil's inductance,
leaving only a small voltage available to light the lamp. Removing the core therefore
increases the voltage applied to the lamp.
8 - False. The current in this type of coil flows in opposite
directions in adjacent turns. Back e.m.f.'s of self-induction are produced in all
of the turns; but since the back e.m.f.'s of mutual induction will all have the
opposite polarity, they cancel out the back e.m.f.'s of self-induction and thus
make the coil "non-inductive."
9 - True. When the slug is moved out of the coil, the "core"
consists of air, and the inductance of the coil is decreased. Since the smaller
magnetic field is able to expand and contract at a faster rate, the coil is now
able to transfer its electrical energy into the resonating capacitor at a higher
Posted October 6, 2020(original