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These two circuit analysis challenges from the March 1967 issue of Radio-Electronics magazine were simple enough that even I figured them out on the first try. The first one requires simply summing currents given the stated resistor and voltage values. For the second problem, note the configuration is that of an autotransformer, then used the provided load current and voltage to work it out based on power out versus power in. That should make it a cinch for anyone else, too. I'm glad there was no "black box" type problem in this set, since those take too much thinking, and my solutions rarely match the author's, and I end up feeling like an idiot. Bon chance.

Conducted by E. D. Clark

Two puzzlers for the student, theoretician and practical man. Simple? Double-check your answers before you say you've solved them. If you have on interesting or unusual puzzle (with an answer) send it to us. We will pay \$10 for each one accepted. We're especially interested in service stinkers or engineering stumpers on actual electronic equipment. We get so many letters we can't answer individual ones, but we'll print the more interesting solutions-ones the original authors never thought of.

Write EQ Editor, Radio-Electronics, 154 West 14th Street, New York, N. Y. 10011.

Transistor Current

In the circuit illustrated, forward bias (base-emitter and base-collector) is 0.5 volt. Is IB (1) greater than IE, (2) smaller than IE, or (3) equal to IE?

- Allan C. Schoening

Current Mystery

In the circuit to the right, the fuse does not blow. Why not?

- Clarence L. Chinn

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.

Transistor Current

Correct answer is (1), for IB is greater than IE. Here's how to figure the currents:

Current Mystery

That portion of the autotransformer winding from B to C appears to the load as a separately wound secondary. Thus the 6-amp current flows only like this:

Section B to C, however, is also a portion of the primary winding, section A to C. The load requirement is 36 watts. Since the complete primary has 117 Vac across it, primary current is only 308 mA (assuming no losses in the autotransformer).

Posted March 29, 2024