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# Transient Voltage QuizJuly 1968 Popular Electronics

 July 1968 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.

This "Transient Voltage Quiz" created by Robert Balin appeared in the October 1968 issue of Popular Electronics magazine. Unless you have done a lot of circuit simulation and/or measurement involving RC time constants, most of these circuit - waveform combinations will probably be foreign to you. Voltages, resistance, and capacitances are not given, so assume if there is more than one of any in a given circuit that they are the same value. Also, a "steady state" is generally considered the time of 5 RC time constants. For example if you have a 2 kΩ resistor and a 1 μf capacitor in series, the time constant is 2E3 x 1E-6 = 2E-3, or 2 milliseconds. Therefore, steady state is assumed to be 5 x 2 ms = 10 ms. It is probably safe to infer the "1" and "2" on the graph horizontal scales represent 5 RC time constants apiece. The actual numerical values and units of time are not important here.

Hint (compliments of yours truly): Probably the easiest problem is 10, since it is the only one that starts out in position 1 with the output of the voltage supply (battery) connected directly to the "+" voltage. Assuming prefect components, the internal resistance of the battery is 0 Ω so the presence of a series RC combination across it has no effect. Looking for a graph showing a full scale steady state voltage from time 0 to time 1, you see there is only one like that - graph E. Done.

Transient Voltage Quiz

By Robert P. Balin

Voltages in circuits containing capacitors increase or decrease as the capacitors charge and discharge. These transient voltages may be useful or destructive depending on where or when they occur. To test your knowledge of how transients develop and decay, match the circuits (1 − 10) to the output voltages (A − J). In each case, the switch is held in position 1 until a steady state is reached, then in position 2 for the same length of time. Don't consider differences in component values.

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.

1 - G

2 - I

3 - F

4 - C

5 - A

6 - D

7 - B

8 - J

9 - H

10 - E

Posted January 12, 2022