April 1967 Popular Electronics
[Table
of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. All copyrights (if any) are hereby acknowledged. |
Here is a quick test of
your graph reading skills. It appeared in the April 1967 edition of Popular Electronics. I missed #6 - a temporary
(hopefully) case of cranial rectumitis on my part. Maybe you will do better.
See all articles from
Popular Electronics.
Graph Interpretation Quiz
By Robert P. Balin
Today's front-line electronic technician must be able to interpret
readily the various charts and graphs devised by engineers to convey important information on the electrical
characteristics of circuits as well as of individual components. In addition, the technician must be thoroughly
familiar with the origin and composition of a variety of unusual as well as standard oscillographic waveforms.
Test your ability to interpret the graphs and waveforms shown below (1-10) by selecting the most likely meaning,
(A) or (B), from the two possibilities given in each case.
1. The family of plate characteristic curves for a triode shows that as the plate voltage is increased the
a.c. plate resistance (A) increases or (B) decreases. |
6. Vacuum-tube mutual transconductance curve indicates that as grid bias is increased mutual
transconductance, Gm, (A) increases or (B) decreases. |
2. The distortion seen in this square-wave test signal indicates that the amplifier being tested is
attenuating the (A) low frequencies or (B) high frequencies. |
7. Of the two load lines, (A) and (B), shown in the graph at right, which one represents the larger value of
load resistance? |
3. The collector current vs. base current curve for a transistor indicates that as the base current is
increased the beta (gain) of the transistor (A) increases or (B) decreases. |
8. The magnetization curve for a transformer core material shows that as the core goes into saturation its
permeability (A) increases or (B) decreases. |
4. This transmitter modulation pattern indicates that the r.f. carrier is (A) over-modulated or (B)
under-modulated |
9. The rate of change of a current depicted by a sine wave is greatest when the current is at its peak (A),
or (B) when it is passing through 0. |
5. Output curves show that as a transistor's collector voltage increases, the a.c. output resistance (A)
increases or (B) decreases. |
10. This frequency response curve for a tuned transformer indicates that the windings are (A) over-coupled or
(B) under-coupled. |
Quiz Answers
1 - B The slope of these curves represents the ratio I
_{p}/E
_{p}, or conductance (the
reciprocal of resistance). As the plate voltage is increased, the slope and conductance also increase, and the
resistance decreases.
2 - A The fundamental and low-frequency components of a square wave contribute chiefly to the center
portion of its flat top. Thus, if an amplifier under test attenuates the low frequencies, a dip appears in the
center of the square-wave test signal.
3 - B The slope of this curve represents the ratio l
_{c}/I
_{B},
or beta, the current gain of a transistor. As the base current increases, the slope of the curve and beta
decrease.
4 - A Overmodulation can reduce an r.f. carrier to zero amplitude during a period of time as shown by the
thin base line through the modulation envelope.
5 - A The slope of this family of curves indicates
changes in the conductance of the transistor. As the collector voltage (V
_{CE}) is increased, the slope
and conductance decrease, and the resistance increases.
6 - B The slope of this curve represents the ratio
I
_{p}/E
_{G}, or mutual conductance (Gm) of this vacuum tube. As the grid voltage (E
_{g})
is increased, the slope and Gm decrease.
7 - B The slope of a load line represents the conductance of the
load resistance. The load line with the lesser slope (B) shows a lower conductance, or higher resistance.
8 - B The slope of this curve reflects the ratio B/H, the permeability of the core material. As the curve goes
over the knee, the slope and permeability both decrease.
9 - B At its peak amplitude, a sine wave changes
from one finite value to another, but as it passes through zero it changes from a finite value to zero, resulting
in an infinite percent change.
10 - A When the windings of a tuned air-core transformer are overcoupled, a dip is produced in the center of an
otherwise single-peaked frequency-response curve, and two new resonant peaks occur at slightly higher and lower
frequencies.
Posted 7/26/2012