December 1954 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.

Maybe given the nature of
the newly introduced Popular Electronics magazine (this was only the third
issue), the editors decided using a big word like "nomograph" might be a little
too out of the realm for use in a magazine seeking to appeal to newcomers to the
electronics field. It is a little surprising since students of the day were quite
accustomed to using this type of a graph since computers still filled entire rooms
and handheld calculators went by a different name 
slide rules.
In fact, because of a familiarity with using a
slide rule, people were
more accustomed to having to shift decimal points to the left or right first to
do the calculation on a device that only displayed values in a single decade range,
and then to arrive at the final answer after the calculation. That is exactly the
skill needed to use the nomograph.
I guess that people today  even engineers  would have a harder time keeping
track of powers of 10 than most reasonably skilled high school math students of
the 1950s.
E, I R, and P Chart
Voltage, Current, Resistance, and Power Nomograph
If you know any two of the four quantities. voltage (E), current (I), resistance,
(R). and power (P), in a circuit, you can find the other two by using this chart.
Using the upper part of the chart. just lay a straightedge between the graduations
corresponding to the two quantities you know, then read the other two quantities
where the straightedge crosses the corresponding lines.
For example, suppose the voltage is 100 volts and current is 30 milliamperes.
The resistance is 3330 ohms (approximately) and the power is 3.0 walls.
If the quantities you have are larger or smaller than any shown in the chart,
you still can find your answer. Move the decimal point in each quantity to bring
it within the range of the chart. In a power figure. move the decimal point a multiple
of three places; in a voltage figure, a multiple of two places. In current and resistance,
the decimal point can be moved any number of places. Then, using the lower part
of the chart, lay your straightedge between the numbers corresponding to the number
of places you must move the decimal point on the chart left or right to get the
quantities you actually have. Read along the straightedge the number of places you
will have to move the decimal point in each answer as given by the chart, to get
the proper decimal point for your actual problem.
For example, suppose that the voltage in the previous example had been 0.01 volt
and the current 0.3 milliampere. To go from 100 volts to 0.01. volt, we must move
the decimal point four places to the left. To go from 30 milliamperes to 0.3 milliampere,
we must move the decimal point two places to the left. In our answers, we must move
the decimal point two places to the left in resistance, giving 33.3 ohms, and six
places to the left in power, giving 0.000003 watt (0.003 milliwatt or 3 microwatts).
END
Nomographs / Nomograms Available on RF Cafe:

Symmetrical T and H Attenuator Nomograph 
Amplifier Gain Nomograph 
Decibel
Nomograph 
Voltage and Power Level Nomograph 
Voltage, Current, Resistance, and Power Nomograph 
Resistor Selection Nomogram 
Resistance and Capacitance Nomograph 
Capacitance Nomograph 
Earth
Curvature Nomograph 
Coil Design
Nomograph 
Voltage, Power, and Decibel Nomograph 
Coil Inductance Nomograph 
Antenna Gain Nomograph

Resistance and Reactance Nomograph 
Frequency / Reactance Nomograph
Posted September 2, 2022 (updated from original post on 7/1/2011)
