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Chapter 11 Electrical Engineering 231
Design
Schematics
When drawing electrical circuitry, it is much easier
to use simple symbols for parts than it is to draw pic-
tures. These basic symbols are called schematic
symbols. A schematic diagram is a basic sketch of cir-
cuitry showing schematic symbols for parts and lines to
represent conductors. Using a schematic diagram, elec-
trical engineers can build or troubleshoot complex cir-
cuitry. Electrical engineers also use schematic diagrams
in the circuit design phase. Figure A shows schematic
symbols for common electronic components.
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Figure A.
Schematic or Circuit Diagram Symbols
Connected
wires
Unconnected
wires
Push-button switch
(normally open)
Single-pole, double-
throw (SPDT) switch
Double-pole, double-
throw (DPDT) switch
+V
Positive (+) voltage
connection
Ground
connection
Resistor Potentiometer
(variable resistor)
Photo-resistor
(light-sensitive resistor)
Ceramic capacitor Electrolytic
capacitor
Diode
Zener diode
Light-emitting diode
(LED)
NPN bipolar
transistor
PNP bipolar
transistor
Power metal-oxide-
semiconductor
field-effect transistor
(MOSFET)
Integrated circuit
(IC)
Meter
Relay
Transformer
Magnetic speaker
Piezoelectric buzzer Fuse