Bridge Circuit Quiz
December 1966 Popular Electronics

December 1966 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.

I found this Bridge Circuit Quiz in my stack of vintage Popular Electronics magazines (I thought all had been posted). I just ordered another batch of Popular Electronics on eBay, so that will provide a dozen or so more quizzes. Your challenge here, compliments of Robert P. Balin, is to decide what the main function of each type of bridge circuit is. Most bridge circuits are designed such that a component of unknown value is inserted into one of its four branches, and then one or more variable components of known values are adjusted to balance the bridge and thereby create a minimum (null) between opposite (circuit-wise) nodes. Admittedly, I did not fare well, but it is because I do not recall having the names associated with many of these bridge circuits. Of course nearly everyone is familiar with the Wheatstone, Kelvin, and Wien bridges. Hyperlinks are provided to information on the bridge circuit theory. I could not find any specific page for Mr. Resonance's bridge, but interestingly many of the pages Google returns has to do with the Tacoma Narrows Bridge (Galloping Gertie) self-destruction due to resonance.

Bridge Circuit Quiz

By Robert P. Balin

Most electronic technicians are familiar with the widely used Wheatstone bridge. But many are not so familiar with other types of bridges commonly used in the laboratory for measurement of impedance-resistive, reactive, inductive, or capacitive - at frequencies well up into the UHF band. Bridges employ the so-called null method to measure an unknown quantity, either directly or by computation. In the latter case, values of some of the fixed and adjustable components in the bridge are substituted in an applicable equation, which is then solved for the unknown quantity. See how many circuits (A-J) you can identify by name (1-10).

See answers below.

Popular Electronics published many quizzes over the years (as did a few other magazines to a lesser extent) - 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.

Answers

1 - J   The Carey Foster bridge measures capacitance in terms of mutual conductance, and mutual conductance in terms of capacitance.

2 - H   The Hay bridge measures the self-inductance of high-Q coils (Q greater than 10), and also determines unknown frequencies.

3 - D   The Heaviside bridge measures the mutual inductance of the coils of a transformer in terms of a known self-inductance and known resistances.

4 - I   The Kelvin bridge is used when extremely low resistances - down to 0.001 ohm - are to be measured.

5 - C   The Maxwell bridge measures the self-inductance of low-Q coils (Q of 10 or less).

6 - F   The Owen bridge, like the Hay and Maxwell bridges, measures the self-inductance of coils. The main difference between the Owen and the other two bridges is that the Owen bridge has the two adjustable components in the same arm.

7 - A   The Resonance bridge measures capacitance, inductance, and frequency.

8 - G   The Schering bridge measures capacitance in terms of a standard capacitor and known resistances.

9 - B   The Wheatstone bridge, oldest of the bridge family, is used where accurate resistance measurements - in the range of 1 ohm to approximately 1 megohm - are to be made.

10 - E   A Wien bridge is used to measure capacitance by comparison with a standard capacitor, and inductance by comparison with a standard inductor.

Posted June 22, 2018