Page 86 - Teach Yourself Electricity and Electronics

66 Basic dc circuits

4-1 At A, a fixed resistor. At
B, a two-terminal variable
resistor. At C, a three
terminal potentiometer.

four parallel lines, long-short-long-short. It’s not necessary to use more than four lines
for any battery, even though sometimes you’ll see six or eight lines. The symbols for a
cell and a battery are shown in Fig. 4-2.

4-2 At A, a single cell. At B, a
battery.

Meters are indicated as circles. Sometimes the circle has an arrow inside it, and the
meter type, such as mA (milliammeter) or V (voltmeter) are written alongside the cir-
cle, as shown in Fig. 4-3A. Sometimes the meter type is indicated inside the circle, and
there is no arrow (Fig. 4-3B). It doesn’t matter which way it’s done, as long as you’re
consistent everywhere in a schematic diagram.

4-3 Meter symbols. At A,
designator outside; at B,
designator inside. Either
symbol is OK.

Some other common symbols include the lamp, the capacitor, the air-core coil, the
iron-core coil, the chassis ground, the earth ground, the alternating-current source, the
set of terminals, and the “black box,” a rectangle with the designator written inside.
These are shown in Fig. 4-4.