Electrical symbols

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Electrical symbols By Muhammad
Ahtsham
Muhammad Ahtsham
Electrical Symbols

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Ahtsham
1890 and 1910,
knob and tube wire
was all the rage in
home building.
History of electrical wiring

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In the 1920's to 1940's, electrical took a turn to a more
protective wiring scheme, flexible armored cable used to
use. It is also known as Greenfield. It was a welcomed
addition to home wiring.

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In the 1940's, finally came the age of metal conduit. This
invention allowed to pull many wires in the same
enclosure.

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The newest addition to wiring was introduced in the
1960's around 1965. It was an update to NM cable that
incorporated the use of a third wire, a bare ground wire
run with a hot and neutral wire.

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Underground feeder wire(UF) was invented to be
buried directly under the ground without having to be
placed in conduit.

A wire is a single
flexible strand or rod
of metal. Wires are
used to pass current
very easily from one
part of the circuit to
another.
Wire Junction
Wire Not connected
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It supplies electrical
energy. The larger terminal
(on the left) is positive (+)
while the smaller (on the
right) is negative (-). A
single cell is often called a
battery, but strictly the
battery is two or more cell
joined together.
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 It converts light
energy into electrical
energy.
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A battery supplies
electrical energy to the
circuit. It is like cell but
the difference is that cell
is considered as one but
the battery is considered
more than one cell.
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It provides the light when
electric current passes
through it. A light bulb
produces light with a
filament wire heated to a
high temperature by an
electric current passing
through it until it glows.
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Fuse
A fuse is a special kind
of resistor that acts as
short circuit (0
resistances) unless the
current exceeds the rated
value. If the current
exceeds a rated value the
fuse blows and acts as an
open circuit (an infinite
resistance).
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 The circuit breaker is a The
circuit breaker is a
mechanical switching
device capable of protecting
the circuit wiring, capable
of making, carrying and
breaking currents under
normal circuit conditions
and also making, carrying
for a specified time and
breaking currents under
specified abnormal circuit
conditions such as short
circuit.
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 (a).It is the lighting lamp transducer
which converts electrical energy to
light. This symbol is used for a lamp
providing illumination.
e.g. A car head lamp or torch bulb.
 b. It is the indicating transducer that
converts electrical energy to light. This
symbol is used for a lamp which is an
indicator.
e.g. A warning light on cars dashboard
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 A device which is only
allows current to flow in
one direction.
 It has low (ideally zero)
resistance to current flow in
one direction, and high
(ideally infinite) resistance
in the opposite direction.
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 It is a light sensitive
diode.
 Photodiode allows
current flow when
exposed to light.
 A photodiode is capable
of converting light into
either current or
voltage, depending
upon the mode of
operation
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 (1). Fixed power source: The free DC
output is fixed to a constant voltage level
by using a voltage controller. If it is used
to produce DC, a rectifier is used to
convert alternating voltage to direct
voltage.
 (2). Variable power source: An AC
power supply typically takes the voltage
from mains supply and lowers it to the
desired voltage
FIXED
Variable
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Resistor
Fixed Resistor: This type of resistor
resists the flow of current.
Variable Resistor: This type of resistor
is used to control the current known as
rheostat.
Variable Resistor Potentiometer: This
type of resistor consist of 3 contacts. It is
used to control the voltage.
Variable resistor Preset: Preset
resistors are used in circuits when it is
necessary to alter the resistance.
1
2
3
4
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AC CURRENT SOURCE:
 AC is the form in
which electric power is
delivered to businesses and
residences. In alternating
current the flow of electric
charge continually changes
the direction.
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DC CURRENT SOURCE:
Direct current (DC) is the unidirectional flow of electric
charge. Direct current is produced by sources such
as batteries, thermocouples, solar cells.
Direct current is used to charge batteries,
and in nearly all electronic systems, as the power supply.
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LED
LED stands for (light
emitting diode). It is a semi-
conductor light source.
LED’s are used in general
lightning, traffic signals and
are used in advance
communication technology.
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 LDR stands for (light dependent
resistor) made up of semi conductor,
they are useful in light/dark sensor
circuits. Normally the resistance of an
LDR is very high, sometimes as high
as
 1000000 ohms, but when they are
illuminated with light resistance drops
dramatically.
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 An electric heater is
an electrical appliance that
converts electrical energy
into heat. The heating
element inside every electric
heater is simply an
electrical resistor, and works
on the principle of Joule
heating.
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 An electric generator is a
device that converts
mechanical energy to electrical
energy. A generator forces
electric current to flow
through an external circuit.
The source of mechanical
energy may be a reciprocating
or turbine steam engine, water
falling through a turbine.
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 An electric motor is an electric
machine that converts electrical
energy into mechanical energy.
 In normal motoring mode, most
electric motors operate through the
interaction between an electric
motor's magnetic field and winding
currents to generate force within
the motor.
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 A transformer is a static electrical device that
transfers energy by inductive coupling
between its winding circuits. A varying
current in the primary coil creates a varying
magnetic flux in the transformer's core and
thus a varying magnetic flux through the
secondary coil.
 This varying magnetic flux induces a varying
electromotive force (emf) in the secondary
coil. Transformers can be used to vary the
relative voltage of circuits or isolate them, or
both.
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RCD
A residual - current
device (RCD) is an electrical
wiring device that disconnects a
circuit whenever it detects that
the electric current is not
balanced between the energized
conductor and the return
neutral conductor.
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 Light tubes are physical
structures used for transporting
or distributing natural or
artificial light for the purpose of
illumination. In their
application to day lighting, they
are also often called tubular day
lighting devices, sun pipes, sun
scopes, or daylight pipes.
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 Electronic sirens are basically
high-performance electronic
amplifiers like in home sound
systems. These sirens work with
substantially higher outputs and
specific demands are placed on
them in terms of desired extreme
reliability and different methods
of their control.
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 A solder bridge is an electrical
connection between two
conductors by means of a small
blob of solder. Solder mask is not
always used for hand soldered
assemblies but is essential for
mass produced boards that are
soldered automatically
using reflow or solder bath
techniques.
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 A thermocouple is a temperature-measuring device consisting of two
dissimilar conductors that contact each other at one or more spots.
 It produces a voltage when the temperature of one of the spots differs
from the reference temperature at other parts of the circuit.
Thermocouples are a widely used type of temperature sensor for
measurement and control.
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 Ground or earth can refer to the
reference point in an electrical
circuit from which voltages are
measure. A common return path
for electric current or a direct
physical connection to the Earth.
SIGNAL GROUND
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Chess ground

 A loudspeaker is an electro
acoustic transducer that
produces sound in
response to an
electrical audio
signal input. Non-electrical
loudspeakers were
developed as accessories
to telephone systems but
electronic amplification
by vacuum tube made
loudspeakers more
generally useful.
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 An electric bell is a
mechanical bell that functions by
means of an electromagnet. When
an electric current is applied, it
produces a repetitive buzzing or
clanging sound. Electric bells have
been widely used at railroad
crossings,
in telephones, fire and burglar
alarms, as school bells, door bells,
and alarms in industrial plants.
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Switches
1. Push switch: A push switch allows
current to flow only when the
button is pressed like switch in
door bell.
2. Push to break switch: This type
of switch is normally closed i.e. on.
It is open only when button is
pressed.
3. SPST: Single Pole, single Throw:
An on—off switch allows current
to flow only when it is closed.
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Switches
4. SPDT: Single Pole, Double
Throw: They are described as on
off on switch.
5. DPST: Double Pole, single
Throw: A dual on off switch often
used to switch main electricity.
6. DPDT: Double Pole, Double
Throw: They are used in motors.
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