# Quiz on AC Circuit TheoryDecember 1970 Popular Electronics

 December 1970 Popular Electronics Table of Contents Wax nostalgic about and learn from the history of early electronics. See articles from Popular Electronics, published October 1954 - April 1985. All copyrights are hereby acknowledged.

Here is a fairly simple quiz on AC circuit analysis. If you are not already comfortable with adding series and parallel circuits containing resistors, capacitors, and inductors, you will appreciate the simple formula presented that will keep the sweat level down ;-)  OK, pick up you pencils... now.

Quiz on AC Circuit Theory

By Robert P. Balin

Voltage measurements made in a series ac circuit seldom add up as simply as they do in a dc circuit. You may even find the voltage across a coil or capacitor to be greater than the supply voltage! Nevertheless, Ohm's Law and Kirchhoff's Law do apply, and careful measurements will show that the supply voltage and the various voltage drops around a series ac circuit are related in an unusual way: the square of the supply voltage is equal to the square of the difference between the voltage on the coil and the voltage on the capacitor, plus the square of the voltage on the resistor.

This relationship, (VTotal)2 = (VL - VC)2 + (VR)2,can be used to find any unknown voltage if all others are known.

In parallel ac circuits, the currents add up the same way as voltages do in a series ac circuit. Brush up on your ac theory and see if you can solve the missing voltage or current in the circuits below. Where necessary, the voltages and currents are related by the 3:4:5 ratio to provide easy, whole number answers. Only simple algebra is required. Vectors, phasors, and quadratic equations are not necessary to find the solutions.

Popular Electronics published many quizzes over the years - some really simple and others not so simple. Robert Balin created many of the quizzes. This is a listing of all I have posted thus far.

 Electronics IQ Quiz - May 1967 Plug and Jack Quiz - December 1967 Electronic Switching Quiz - October 1967 Electronic Angle Quiz - September 1967 International Electronics Quiz - July 1967 Bridge Circuit Quiz -December 1966 Diode Function Quiz - August 1965 Diagram Quiz, August 1966 TV Trouble Quiz, July 1966 Electronics History Quiz, December 1965 Scope-Trace Quiz, March 1965 Electronic Circuit Analogy Quiz, April 1973 Test Your Knowledge of Semiconductors, August 1972 Ganged Switching Quiz, April 1972 Lamp Brightness Quiz, January 1969 Lissajous Pattern Quiz, September 1963 Electronic Quizoo, October 1962 Electronic Photo Album Quiz, March 1963 Electronic Alphabet Quiz, May 1963 Quiz: Resistive? Inductive? or Capacitive?, October 1960 Vector-Circuit Matching Quiz, June 1970 Inductance Quiz, September 1961 RC Circuit Quiz, June 1963 Diode Quiz, July 1961 Electronic Curves Quiz, February 1963 Electronic Numbers Quiz, December 1962 Energy Conversion Quiz, April 1963 Coil Function Quiz, June 1962 Semiconductor Quiz - February 1967 Unknown Frequency Quiz - September 1965 Electronics Metals Quiz - October 1964 Electronics Measurement Quiz - August 1967 Meter-Reading Quiz, June 1966 Electronic Geometry Quiz, January 1965 Electronic Factor Quiz, November 1966 Electronics Math Quiz, November 1965 Series Circuit Quiz, May 1966 Electrochemistry Quiz, March 1966 Electronic Analogy Quiz, November 1961 Electronic Coupling Quiz, August 1973 Electronics Analogy Quiz, August 1960 Audio Quiz, April 1955 Electronic Unit Quiz, May 1962 Capacitor Circuit Quiz, June 1968 Quiz on AC Circuit Theory, December 1970 Magnetic Phenomena Quiz, February 1962 Electronics Geography Quiz, April 1970 Electronic Menu Quiz, August 1963 Electronic Noise Quiz, August 1962 Electronic Current Quiz, October 1963 Electronic Inventors Quiz, November 1963 Resistor Function Quiz, January 1962 Electronic Measurement Quiz, January 1963 Vacuum Tube Quiz, February 1961 Kool-Keeping Kwiz, June 1970

1. (10)2= (8)2 + (VR)2; VR = 6V

2. (20)2= (7+VC)2+ (12)2; VC = 9V

3. (24)2= (VL-6)2; VL = 30V

4. (15)2= (350-350)2+ (VR)2; VR = 15V

5. (VT)2= (15-3)2+ (16)2; VT = 20V

6. (50)2= (VL)2+ (12)2= (VC)2+ (12)2; VL = VC

(VT)2= (VL-VC)2+ (12)2; VT = 12V

7. (IT)2= (6)2+ (8)2; IT = 10 mA.

8. (20)2= (16-IC)2+ (16)2; IC = 4 mA.

9. (IT)2= (17-13)2+ (3)2; IT = 5 mA.

10. (9)2= (40-4-IC)2; IC = 7 mA.

Posted June 21, 2013

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