Here are three more puzzlers from the "What's Your EQ?" section of the May 1963 issue of Radioâˆ’Electronics magazine. The Constant Current circuit has two solutions, of which the first - the one I solved (hint: first solve for the circuit impedance needed for the given voltage and current) - is the simplest and most intuitive. You're probably smarter than I am and will naturally arrive at the more sophisticated solution. Four-Way Switch is a piece of cake it you've done electrical wiring (hint: you can make another configuration switch from a 4-way). Don't let the vacuum tube diodes throw you on Rectified Voltage; just replace the symbols with semiconductor diodes (hint: the fat line is the plate = anode). Good luck.

Three puzzlers for the student, theoretician and practical man. They may look simple, but double-check your answers before you say you've solved them. If you've got an interesting or unusual answer send it to us. We are especially interested in service stinkers or engineering stumpers on actual electronic equipment. We are getting so many letters we can't answer individual ones, but we'll print the more interesting solutions (the ones the original authors never thought of). We will pay \$10 and up for each one accepted. Write EQ Editor, Radio-Electronics, 154 West 14th St., New York, N. Y.

Answers for this month's puzzlers are on at the bottom.

Constant Current

Current flow in the circuit here is 732 ma. When C is shorted, the current remains at 732 ma. Find XC. - S. K. Allen

Four-Way Switch

"Three-way switches" are used when it is desired to operate a device (such as a light on a stairway) that can be turned on or off with either of two switches. Here we have a problem in which it is desired to turn the light on or off with anyone of three switches.

The three switches are dpdt, hooked up as reversing switches, as shown. How are they to be wired so that the light can be turned on or off by switching anyone of them? - John E. Glasner

Rectified Voltage

What is the rectified voltage across RL with both tubes connected, as shown in the above circuit? The indicated plate voltages are peak voltages, and the volt-age drop across each mercury-vapor rectifier tube is considered to be constant at 15 volts when the tube is conducting. - Paul F. Brown

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.

These are the answers. Puzzles are on page 34.

Constant Current

There are two possible answers. The first is that C is shorted, and XC is therefore zero. Putting another short across C would then have no effect on the circuit. The second answer is, since 732 ma flows in the circuit, the total opposition must be 157 ohms. Since XL and XC are in 180° opposition to each other, we can find our answer by simple subtraction. Subtracting XC from XL, we find XC equal to zero. Subtracting XL from XC to get 157 ohms, XC must be equal to 314 ohms. Thus, shorting it out leaves the 157 ohms in circuit.

Note that with XC in circuit, we have a capacitive circuit, the current leading the voltage by 90°; but when XC is shorted out, while the ohmage remains the same, the current now lags the voltage by 90°.

Four-Way Switch

The switches are hooked together as shown, so that the light can be turned on or off with anyone of the three switches. Note that the wiring is repetitive - any number of switches could be connected to the circuit.

Rectified voltage

If the lower tube only is used in the circuit, the voltage across RL is 150 - 15, or 135 volts. If the upper tube only is used, the voltage across RL is 300 - 15, or 285 volts. The top of RL connected to the cathode is positive, of course, in both cases. If both tubes are inserted at the same time, the top of RL is 285 volts (positive) while the plate of the lower tube is 150 volts (positive). Therefore the lower plate voltage is 285 - 150, or 135 negative, with respect to its cathode potential, and the lower tube does not function as a rectifier. The situation remains the same as if the upper tube alone were inserted.

Posted May 26, 2023