Search RFCafe.com                           
      More Than 18,000 Unique Pages
Please support me by ADVERTISING!
Serving a Pleasant Blend of Yesterday, Today, and Tomorrow™ Please Support My Advertisers!
   Formulas & Data
Electronics | RF
Mathematics
Mechanics | Physics
     AI-Generated
     Technical Data
Pioneers | Society
Companies | Parts
Principles | Assns
 About | Sitemap
Homepage Archive		         Resources
Articles, Forums Calculators, Radar
Magazines, Museum
Radio Service Data
Software, Videos		      Entertainment
Crosswords, Humor Cogitations, Podcast
Quotes, Quizzes
   Parts & Services
1000s of Listings		  Vintage Magazines
Electronics World
Popular Electronics
Radio & TV News
QST | Pop Science
Popular Mechanics
Radio-Craft
Radio-Electronics
Short Wave Craft
Electronics | OFA
Saturday Eve Post
Software: RF Cascade Workbook
RF Stencils for Visio | RF Symbols for Visio
RF Symbols for Office | Cafe Press
Espresso Engineering Workbook

Aegis Power  |  Alliance Test
Centric RF  |  Empower RF
ISOTEC  |  Reactel  |  RFCT
San Fran Circuits
PCB Directory (Manufacturers)

Temwell Filters

Noisecom

Please Support RF Cafe by purchasing my  ridiculously low-priced products, all of which I created.

RF Cascade Workbook for Excel

RF & Electronics Symbols for Visio

RF & Electronics Symbols for Office

RF & Electronics Stencils for Visio

RF Workbench

T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads

These Are Available for Free

Espresso Engineering Workbook™

Smith Chart™ for Excel
DC-70 GHz RF Cables - RF Cafe

Voltage Quiz
December 1961 Popular Electronics

December 1961 Popular Electronics

December 1961 Popular Electronics Cover - RF CafeTable 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.

Popular Electronics magazine's quizmeister Robert P. Balin created this "Voltage Quiz" for the December 1961 issue. Fortunately, only fixed resistors (6 Ω each) and battery voltage source(s) are involved. The goal is to calculate the voltage at point "A" with respect to ground. Analyzing some of the circuits is made easier by rearranging the layout to remove wiring overlaps. Circuit 5 might be the simplest of all, and can be done fairly easily in your head. Others, like circuit 1, are best approached by writing two mesh equations per Kirchhoff's voltage law (the sum of all voltages in a closed circuit equals zero) and solving the resulting two equations in two unknowns (basic algebra). Spoiler: Upon redrawing a couple circuits you might discover an identical instance of a previous one, making the solution the same as well. A big list of other quizzes is given below.

Voltage Quiz

Voltage Quiz, December 1961 Popular Electronics - RF CafeBy Robert P. Balin

Can you determine the voltage and polarity of point A with respect to ground in each of the seven circuits shown below? All resistors measure six ohms and each battery produces six volts d.c. You'll find it helpful to use pencil and paper in working out the problems. Write the answers in the spaces provided under the diagrams.

 

***

Quizzes from vintage electronics magazines such as Popular Electronics, Electronics-World, QST, Radio-Electronics, 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

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Voltage Quiz Answers

In each problem, the schematic diagram shown on page 69 must be redrawn for the sake of clarity. The solution to the problem should then become apparent. Remember that each resistor is six ohms.

Voltage Quiz Answer (1), December 1961 Popular Electronics - RF Cafe1) Kirchhoff's law states that the algebraic sum of the products of the current and resistance in any closed path in a network is equal to the voltages connected in the same path. Setting up two simultaneous equations, we solve for current 12, then determine the voltage drop across R4 which is voltage A:

(1) 6= 6I1+ 6(I1 - I2)

(2) 0= 6(I2 - I1) + 12I2

Now separate variables I1 and I2:

(1) 6= 12I2 - 6I2

(2) 0 = -6I1 + 18I2

Divide equation (1) by 2 and add equations (1) and (2):

3 = 15I2

I2 = 0.2 ampere

Now solve for voltage A:

Ea =R4 x -I2

Ea = 6 x -0.2 = -1.2 volts

 

Voltage Quiz Answer (2), December 1961 Popular Electronics - RF Cafe2) The symmetry of the redrawn circuit suggests that voltage A is at ground potential (or 0 volt). Remove R5 from the circuit and note that currents flowing through resistor branches R1-R4 and R2-R3 are equal. Hence, the voltages at the midpoint of both branches are equal or point A is at ground potential. Now insert R5 (which could be any value from zero ohm to infinity). Since point A is at ground potential, no current will flow through R5. This can be proved using Kirchhoff's law and setting up three simultaneous equations.

 

Voltage Quiz Answer (3), December 1961 Popular Electronics - RF Cafe3) The redrawn version of the schematic is identical to the one shown above in Answer 1 except that the battery is connected backwards. So, voltage A is the same as in Answer 1 change in sign, or +1.2 volts.

 

 

Voltage Quiz Answer (4), December 1961 Popular Electronics - RF Cafe4) Redrawn, the circuit is simplicity itself. It is easy to determine the current flowing through the loop consisting of the battery, R1, R2 and R3 (1/3 ampere). The voltage at point B is determined by the IR drop across R3 (-2 volts) . Since no current flows through resistor R4 to point A, both point A and point B are at the same potential: -2 volts.

 

 

Voltage Quiz Answer (5), December 1961 Popular Electronics - RF Cafe5) A glance at the redrawn circuit suggests that resistors R1, R2, R3 and R5 be combined mathematically into one resistor (found to be 6 ohms) and, resorting to Ohm's law, the voltage at point A is +3 volts.

 

 

Voltage Quiz Answer (6), December 1961 Popular Electronics - RF Cafe6) The original schematic, impressively complicated in appearance, becomes straightforward when redrawn as above. It is simply a problem of combining resistors R2 and R3 mathematically and computing current flow. Once done, the voltage drop across R1 is computed to be +2 volts.

 

 

Voltage Quiz Answer (7), December 1961 Popular Electronics - RF Cafe7) Here again it is wise to combine resistors R1, R2 and R4 mathematically into one resistor and then resort to Ohm's law. The current through R3 is six-tenths of an ampere. Thus, we find that the voltage drop across the R1, R2 and R4 resistor combination is +2.4 volts.

 

 

Posted October 24, 2023
DC-70 GHz RF Cables - RF Cafe

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024

Webmaster:

    Kirt Blattenberger,

    BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

Copyright  1996 - 2026

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website: AirplanesAndRockets.com

My Daughter's Website: EquineKingdom
LadyBug RF Power Sensors

Windfreak Technologies Frequency Synthesizers - RF Cafe

everythingRF RF & Microwave Parts Database (h1)