# What's Your EQ (Electronics Quotient)?April 1963 Radio-Electronics

 April 1963 Radio-Electronics [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.

"What's Your EQ?" (Electronics Quotient, a la IQ - Intelligence Quotient) was a feature run in Radio−Electronics magazine for a couple years in the early 1960's. It was a quiz for challenging your knowledge of basic electronic circuit functions. Most of them are relatively simple exercises in voltage division, resistor-capacitor (RC) and resistor-indictor (RL) time constants, resonant frequency, and transformer input/output ratios (voltage and/or current and/or power). Sometimes, the first step in solving the poser is to rearrange the schematic into a more familiar configuration. Also, read the wording carefully to determine whether parts of the circuit can be ignored. Answers are at the bottom of the page. Note that I do not agree with the magazine's answer for the "How Much Voltage?" circuit. My solution is presented below with the rest of the answers.

What's Your Electronics Quotient?

Time constant

Suppose you have two 1-megohm resistors and a 1-μf 50-vdc capacitor. Using a 100-vdc supply voltage, how can you connect these resistors to provide a time constant of 0.5 second, without exceeding the 50-volt rating of the capacitor? - Earl H. Rogers

Series Resistor Circuit

In the circuit shown to the right, the vtvm reads 24 volts. A 100-ohm resistor paralleled with R1 raises the voltmeter reading to 40 volts. The same resistor paralleled with R2 reduces the voltmeter reading to 20 volts. What are the ohmages of resistors R1 and R2 and what is voltage E?

- L. B. Hedge

A Problem of Resonance

Inductance L and capacitor C in the circuit to the left form a series-resonant circuit used in a radio command system. The L-C combination is driven by a variable frequency voltage source having a source resistance R and a peak output of 1 volt. What is the minimum permissible capacitor working voltage in such a circuit?

- Phil Cutler

How Much Voltage?

What is the steady-state DC input voltage, Ein, in the circuit to the right?

- E. R. Welsh

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.

 RF Cafe Quizzes Vintage Electronics Magazine Quizzes RF Cafe Quiz #71: Tech Headlines for Week of 3/13/2023 RF Cafe Quiz #70: Analog & RF Filter Basics RF Cafe Quiz #69: RF Electronics Basics RF Cafe Quiz #68: RF & Analog Company Mergers & Acquisitions in 2017 RF Cafe Quiz #67: RF & Microwave Company Name Change History RF Cafe Quiz #66: Spectrum and Network Measurements RF Cafe Quiz #65: Troubleshooting & Repairing Commercial Electrical Equipment RF Cafe Quiz #64: Space-Time Adaptive Processing for Radar RF Cafe Quiz #63: Envelope Tracking Power Amplifiers RF Cafe Quiz #62: Stimson's Introduction to Airborne Radar RF Cafe Quiz #61: Practical Microwave Circuits RF Cafe Quiz #60: Ten Essential Skills for Electrical Engineers RF Cafe Quiz #59: Microwave Circulator Design RF Cafe Quiz #58: Microwave and Millimeter-Wave Electronic Packaging RF Cafe Quiz #57: Frequency-Agile Antennas for Wireless Communications RF Cafe Quiz #56: Tube Testers and Electron Tube Equipment RF Cafe Quiz #55: Conquer Radio Frequency RF Cafe Quiz #54: Microwave Mixer Technology and Applications RF Cafe Quiz #53: Chipless RFID Reader Architecture RF Cafe Quiz #52: RF and Microwave Power Amplifiers RF Cafe Quiz #51: Antennas and Site Engineering for Mobile Radio Networks RF Cafe Quiz #50: Microstrip Lines and Slotlines RF Cafe Quiz #49: High-Frequency Integrated Circuits RF Cafe Quiz #48: Introduction to Infrared and Electro-Optical Systems RF Cafe Quiz #47: LCP for Microwave Packages and Modules RF Cafe Quiz #46: RF, Microwave, and Millimeter-Wave Components RF Cafe Quiz #45: Dielectric and Thermal Properties of Materials at Microwave Frequencies RF Cafe Quiz #44: Monopulse Principles and Techniques RF Cafe Quiz #43: Plasma Antennas RF Cafe Quiz #42: The Micro-Doppler Effect in Radar RF Cafe Quiz #41: Introduction to RF Design Using EM Simulators RF Cafe Quiz #40: Introduction to Antenna Analysis Using EM Simulation RF Cafe Quiz #39: Emerging Wireless Technologies and the Future Mobile Internet RF Cafe Quiz #38: Klystrons, Traveling Wave Tubes, Magnetrons, Crossed-Field Amplifiers, and Gyrotrons RF Cafe Quiz #37: Component Reliability for Electronic Systems RF Cafe Quiz #36: Advanced RF MEMS RF Cafe Quiz #35: Frequency Synthesizers: Concept to Product RF Cafe Quiz #34: Multi-Gigabit Microwave and Millimeter-Wave Wireless Communications RF Cafe Quiz #33: Battlespace Technologies: Network-Enabled Information Dominance RF Cafe Quiz #32: Modern Communications Receiver Design and Technology RF Cafe Quiz #31: Quantum Mechanics of Nanostructures RF Cafe Quiz #30: OFDMA System Analysis and Design RF Cafe Quiz #29: Cognitive Radar RF Cafe Quiz #28: Human-Centered Information Fusion RF Cafe Quiz #27: Remarkable Engineers RF Cafe Quiz #26: Substrate Noise Coupling in Analog/RF Circuits RF Cafe Quiz #25: Component Reliability for Electronic Systems RF Cafe Quiz #24: Ultra Low Power Bioelectronics RF Cafe Quiz #23: Digital Communications Basics RF Cafe Quiz #22: Remember the Basics? RF Cafe Quiz #21: Wireless Standards Knowledge RF Cafe Quiz #20: Famous First Names RF Cafe Quiz #19: Basic Circuit Theory RF Cafe Quiz #18: Archaic Scientific Words & Definitions RF Cafe Quiz #17: Inventors & Their Inventions RF Cafe Quiz #16: Antennas RF Cafe Quiz #15: Numerical Constants RF Cafe Quiz #14: Oscillators RF Cafe Quiz #13: General Knowledge RF Cafe Quiz #12: Electronics Corporations Headquarters RF Cafe Quiz #11: Famous Inventors & Scientists RF Cafe Quiz #10: A Sampling of RF & Wireless Topics RF Cafe Quiz #9: A Smorgasbord of RF Topics RF Cafe Quiz #8: Hallmark Decades in Electronics RF Cafe Quiz #7: Radar Fundamentals RF Cafe Quiz #6: Wireless Communications Fundamentals RF Cafe Quiz #5: Company Logo Recognition RF Cafe Quiz #4: General RF Topics RF Cafe Quiz #3: General RF/Microwave Topics RF Cafe Quiz #2: General RF Topics RF Cafe Quiz #1: General RF Knowledge 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 Post What's Your EQ? - May 1963 Radio-Electronics Bridge Function Quiz - September 1969 Radio-Electronics What's Your EQ? - March 1963 Radio-Electronics What's Your EQ? - February 1967 Radio-Electronics Circuit Quiz - June 1966 Radio-Electronics What's Your EQ? - June 1966 Radio-Electronics Electronics Mathematics Quiz - June 1969 Popular Electronics Brightest Light Quiz - April 1964 Popular Electronics What's Your EQ? - April 1963 Radio-Electronics Electronics "B" Quiz - July 1969 Popular Electronics Ohm's Law Quiz - March 1969 Popular Electronics Antenna Quiz - November 1962 Electronics World Color Code Quiz - November 1967 Popular Electronics CapaciQuiz - August 1961 Popular Electronics Transformer Winding Quiz - December 1964 Popular Electronics Audiophile Quiz - November 1957 Radio-electronics Capacitor Function Quiz - March 1962 Popular Electronics Greek Alphabet Quiz - December 1963 Popular Electronics Circuit Designer's Name Quiz - July 19680 Popular Electronics Sawtooth Sticklers Quiz - November 1960 Radio-Electronics Elementary Radio Quiz - December 1947 Radio-Craft Hi-Fi 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 Electronic Switching Quiz - October 1967 Popular Electronics Electronic Angle Quiz - September 1967 Popular Electronics International 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 1953 QST TV Trouble Quiz, July 1966 Popular Electronics Electronics History Quiz, December 1965 Popular Electronics Scope-Trace Quiz, March 1965 Popular Electronics Electronic 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 Electronic 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 Inductance 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 Television I.Q. Quiz - October 1948 Radio & Television News Amplifier Quiz Part I - February 1964 Popular Electronics Semiconductor Quiz - February 1967 Popular Electronics Unknown Frequency Quiz - September 1965 Popular Electronics Electronics Metals Quiz - October 1964 Popular Electronics Electronics Measurement Quiz - August 1967 Popular Electronics Meter-Reading Quiz, June 1966 Popular Electronics Electronic Geometry Quiz, January 1965 Popular Electronics Electronic Factor Quiz, November 1966 Popular Electronics Electronics Math Quiz, November 1965 Popular Electronics Series Circuit Quiz, May 1966 Popular Electronics Electrochemistry Quiz, March 1966 Popular Electronics Biz Quiz: Test Your Sales Ability - April 1947 Radio News Electronic Analogy Quiz, November 1961 Popular Electronics Electronic 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 Capacitor 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 Electronic 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

Answers

Time Constant

The maximum voltage the capacitor sees is the steady-state de voltage of 50 across R2. Using Thévenin's theorem, the resistance that the capacitor sees is between points A and B, looking back into the circuit with the source shorted, or the equivalent of R1 and R2 in parallel, or 500,000. Note the circuit is broken at points A and B when determining the Thévenin's equivalent resistance.

Series Resistor Circuit

The solution is shown in image to the left.

That Resonant Problem

The capacitor voltage is maximum at resonance and equal to Q times the input voltage, E. The resonant frequency is 0.159/√LC = 159 cycles. The inductive reactance at resonance is 2πfL = 1,000 ohms. The circuit Q at resonance is Qr = XL/R = 100. Therefore the peak voltage the capacitor must withstand is QE = 100 volts.

How Much Voltage?

1. E across the two capacitors 0.9Ein - 0.6Ein

2. E across the 1-μf capacitor 2/3 (0.9Ein - 0.6Ein)

3. E across the 10,000-ohm resistor = 0.1Ein

4. 2/3 (0.3in) - 0.1Ein = 10 Therefore, Ein = 100 volts dc.

*** I disagree with the magazine's answer. See my solution to the right.

Posted February 28, 2023

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