December 1970 Popular Electronics
Wax nostalgic about and learn from the history of early electronics. See articles
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 ;-) . An even simpler form that solves explicitly for the four variables are as follows:
VTotal = √ [(VL - VC)2 + VR2]
VR = √ [(VT)2 - (VL - VC)2]
VL = VC + √ [VT2 - VR2]
VC = VL - √ [VT2 - VR2]
OK, pick up your 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, VTotal2 = (VL - VC)2 + VR2,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.
(See answers below)
See answers below.
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.
- A Baffling Quiz
- January 1968
- Electronics IQ Quiz
- May 1967
- Plug and Jack Quiz
- December 1967
Switching Quiz - October 1967
Angle Quiz - September 1967
Electronics Quiz - July 1967
- Bridge Circuit
Quiz -December 1966
- Diode Function
Quiz - August 1965
- Diagram Quiz, August
- TV Trouble Quiz,
- Electronics History Quiz,
- Scope-Trace Quiz,
Circuit Analogy Quiz, April 1973
Your Knowledge of Semiconductors, August 1972
- Ganged Switching
Quiz, April 1972
- Lamp Brightness
Quiz, January 1969
- Lissajous Pattern Quiz, September 1963
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
Quiz, September 1961
- RC Circuit
Quiz, June 1963
- Diode Quiz,
- Electronic Curves Quiz, February 1963
- Electronic Numbers Quiz, December 1962
- Energy Conversion Quiz, April 1963
Function Quiz, June 1962
Quiz - February 1967
- Unknown Frequency
Quiz - September 1965
Metals Quiz - October 1964
Measurement Quiz - August 1967
- Meter-Reading Quiz,
Geometry Quiz, January 1965
Factor Quiz, November 1966
Math Quiz, November 1965
- Series Circuit Quiz,
Quiz, March 1966
- Electronic Analogy
Quiz, November 1961
Coupling Quiz, August 1973
- Electronics Analogy Quiz, August 1960
- Audio Quiz,
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
Function Quiz, January 1962
- Electronic Measurement Quiz, January 1963
Tube Quiz, February 1961
- Kool-Keeping Kwiz, June
- Find the
Brightest Bulb Quiz, April 1960
Circuit Quiz Answers
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 May 17, 2019 (original 6/21/2013)