Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
This vector circuit matching
quiz will hurt the brain a little more than most of the ones that were printed in
Popular Electronics. In order to score well, it helps to visualize the circuits
relative to where they would appear on a Smith Chart. Capacitive impedances lie
in the bottom half and have negative phases (-s, -jω). Inductance lie in the
upper half and have positive phases (s, jω). The familiar 'ELI the ICE man' mnemonic
helps, too. Be sure to pay attention to the color of the vector arrow heads.
Example: In a purely inductive circuit like #4, voltage leads current by 90°.
Since phase rotation is CCW, you need to look for lettered phase diagram where the
white arrowhead (voltage) is 90° ahead of the black arrow head (current), going
in the CCW direction. Vector diagram letter 'H' looks like that. Circuit #10, being
purely capacitive, is just the opposite, so its vector diagram is...? Resistance
in parallel or series with reactance adjusts the phase angle somewhere between 0°
and 90° (not lying on an axis line). The rest are
Vector-Circuit Matching Quiz
By Robert P. Balin
Vector diagrams are widely used to show the magnitude and phase relationships
between voltages and currents in an a.c. circuit. A knowledge of vectors is a must
for understanding the theory behind frequency modulation and detection, color TV
and feedback circuits.
Ten circuits (1-10) are shown below; vector diagrams (A-J) representing the voltages
and currents in the circuits are also shown. To test your knowledge of vectors,
match the diagrams to the circuits. Note that this is a simple matching quiz - obviously
special cases might exist if the effects of resonance were considered. It is also
assumed that all elements are pure (that is, capacitors have only capacitance, inductors
only inductance, and resistors only resistance).
Standard counterclockwise vector rotation is used to indicate angles of lead
and lag. A white arrowhead represents a voltage vector; a
black arrowhead is a current vector. In all cases, the reference
is the line along the horizontal, extending to the right. Relative vectors are shown
for all voltages and currents in each circuit.
See answers below.
Popular Electronics published many quizzes over the years
- some really simple and others not so simple. Robert P. 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 Part I - February 1964
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
Vector-Circuit Quiz Answers
1-B In a series circuit containing only resistance, the current is in phase with
the applied voltage.
2-F In a parallel circuit, there are three currents and a single voltage, which
is used as the reference vector (directed horizontally to the right). The current
in an inductor lags the voltage across the inductor by 90 degrees. The current into
a capacitor leads the voltage across the capacitor by 90 degrees. The total circuit
current is the difference between the branch currents.
3-J The current is used as the reference vector. The voltage drops across the
capacitor and resistor add vectorially to equal the applied voltage.
4-H The applied voltage is the reference vector. The current in the circuit lags
the voltage by 90 degrees.
5-G The applied voltage is the reference vector. The two branch currents add
vectorially to equal the circuit current.
6-A The current is used as the reference vector. The voltage drops across the
resistor and inductor add vectorially to equal the applied voltage.
7-I The current is the reference vector. The voltage drops across the inductor
and capacitor are 180 degrees out of phase, and the difference between them is equal
to the applied voltage.
8-E The applied voltage is the reference. The leading currents in each branch
are in phase and add to equal total circuit current.
9-D The applied voltage is the reference. The two branch currents add vectorially
to equal total circuit current.
10-C The applied voltage is the reference. The current in the inductor leads
the applied voltage by 90 degrees.
Posted March 22, 2019(original June 4, 2014)