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What's Your EQ?
February 1963 Radio-Electronics

February 1963 Radio-Electronics

February 1963 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

Three more problems await your attention here to challenge your Electronics Quotient (EQ), compliments of the February 1963 issue of Radio-Electronics magazine. First in line is figuring a way to determine which of five boxes of resistors contains mismarked components. It's a variation on a fairly common way to test components. The second is another Black Box; it's a bit simpler than usual. Hint: WWTD? (What would Thévénin do?). The third is a typical method of wiring a series of switches so that a device can be turned on or off from any number of locations. I recently implemented such a wiring job to control basement lights from four doorways - no big deal. Have fun.

What's Your EQ?

What's Your EQ?, February 1963 Radio-Electronics - RF CafeEfficient Measurement

A dealer receives five boxes full of carbon resistors. Each resistor is marked with three red bands and one gold. The factory sends notice that one of the boxes should have had orange rather than red for the second band. The dealer tells his assistant to locate the defective box with four ohmmeter measurements. The assistant does it with only one measurement. How?

- Albert S. Lombard

 

Open Circuit - RF CafeOpen Circuit

Here we have a two-terminal black box which apparently has some kind of internal power supply. Shorting the terminals gives us a circuit carrying 5 amperes (Fig. 1). The researcher picks up a convenient resistor and places it across the terminals (Fig. 2). Now 3 amperes flow, and the voltage drop across the resistor is 32. What will the terminal voltage be if no current is drawn?

- Charles S. Bryant.

 

Lights and Chicken Farmer - RF CafeLights and Chicken Farmer

A chicken farmer has four chicken houses and his home arranged as shown. He uses one powerful lamp in the center to illuminate the whole area so he can see to go from one house to another. When he arrives at any building, he wants to turn the lamp off. When night catches him indoors, he wants to turn the light on before going out. This can be done with only two hot wires from house to house and, of course, the lamp will have to be connected. (Hint: one lamp wire from the farmer's home, and one from one of the chicken houses.) Use only three dpdt switches and two spst switches.

- Ray McQueen

Quizzes from vintage electronics magazines such as Popular Electronics, Electronics-World, QST, Radio-Electronics, 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.

RF Cafe Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Answers to What's Your Eq?

(These are answers-See puzzles p. 47)

 

Efficient Measurement Solution - RF CafeEfficient Measurement

The assistant takes one resistor from box A, two from B, three from C, four from D, connects them in series and applies the ohmmeter as shown.

If the series runs 100 ohms over 22,000 ohms, box A is the mismarked one; 200 ohms high points to B; 300 to C, and 400 to D. If the series is exactly 22,000 ohms, obviously E is the high box.

 

Open Circuit Solution - RF CafeOpen Circuit

Use Thevenin's theorem. Assume a Thévénin voltage source and a series Thévénin resistance. With output shorted, V = RI, Vt = 5Rt. With the series resistor inserted, Vt = 3Rt + 32. Substituting, we find that 5Rt = 3Rt + 32.

Thus 2Rt = 32, and Rt = 16 ohms. Going back to our original, R = 16 ohms, I = 5 amperes. V, then, equals 80 volts. If no current is drawn, there is no drop across Rt, output voltage is 80.

 

Lights and Chicken Farmer Solution - RF CafeLights and Chicken Farmer

The drawing is self-explanatory.

 
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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a lady's voice announced "You've Got Mail" when a new message arrived...

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