January 1945 Radio-Craft
[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
This Electronic Puzzle Square,
compliments of Lt. C.K. Johnson, appeared in the January 1945 issue of Radio-Craft
magazine. It consists of electronics-related numerical questions whose answers,
if correct, create a 4x4 matrix whose columns, rows, and long diagonals all
add up to 45. Non-integer answers need to be rounded according to standard rules
(do not just truncate). In case you left your slide rule at the office, a link
is provided to assist with Q2. The biggest head scratcher question is Q4, since
it requires the conversion from polar to rectangular coordinates, but hey, you're
an engineer (or a crack technician). Having Euclid on-hand for Q5 might be helpful.
A link is provided to a copper wire parameter table for Q9. Have fun.
Here is another
Square from the July 1945 issue.
Electronic Puzzle Square
By Lt. C. K. Johnson
Here is a new idea in a Magic Square. Work problem No. 1 and put the answer
in square No. 1. The answer to problem 2 goes in square 2, etc. When all 16
problems are completed, the rows, columns diagonals and various other combinations
will total a number which is the type number of a popular power amplifier triode
frequently used push-pull to give a power output of about 18 watts with 275
volts on the plate.
The numbers add up to 45 in every direction,
if answers are correct.
1. The total resistance between A and B is ____ ohms.
2. On a
slide rule, 64 on the right hand side of the A scale is directly over ____
on the D scale.
3. The pentode is a ____ element tube.
4. 21.18/8.1° would equal ____ +3j in rectangular coordinates.
5. If a regular hexagon is inscribed in a circle whose radius is one inch,
the perimeter of the hexagon is ____ inches.
6. What is the voltage between A and B?
7. Two 12 volt batteries hooked in parallel will give ____ volts.
8. 0.142857 is the reciprocal of _____.
9. B&S gage bare copper wire No. ____ has a circular mil area of 1,288
and at 25 °C. has a resistance of 8.1 ohms per 1,000 feet. (see table
10. To find wavelength in meters when frequency in kilocycles is known, we
have a formula λ = (c x 105)/f
. What digit does "c" replace?
11. In the R.M.A. color code, silver represents a tolerance of what percent?
12. What is the total capacitance in mfd. between A and B?
13. Effective voltage (in alternating current of sine-wave form) is to average
voltage as 10 is to ____ .
14. What will be the voltage across the 1-megohm resistor exactly 1.967 seconds
after the switch (S1) is closed, allowing current to enter the resistor-condenser
15. In this circuit the problem is to find the current in milliamperes if
1.62 watts is dissipated in the 500-ohm resistor.
16. Yellow is ____ in the color code.
Posted February 25, 2021