Symbols of Main Electrical Components Video Lecture | Science Class 7

symbols are simplified representations
of actual devices they are used to
represent electrical components in
electrical drawings and diagrams a
device's symbol includes a distinctive
shape that represents the device and an
indication of where its terminals are
connected when used in a circuit the
terminal is a place on a device where a
connection can be made to either a
conductor or another component terminals
may be in the form of a screw post
protruding wire that has been connected
to the device by the manufacturer or
some other type most of the components
we will study in the DC portion of this
course have two terminals later we will
introduce devices with three or even
more terminals here are some very common
electrical devices and their symbols a
lamp is a common electrical load recall
from the last section that a load is a
device that converts electrical energy
into some other form of energy a lamp is
a load that converts electrical energy
into light energy a cell is one type of
a DC power source strictly speaking the
symbol for a single cell is the one
shown here with one long and one short
line however it is common practice to
represent any battery regardless of the
number of cells it contains with only
two cells drawn
as you know batteries are marked with a
positive terminal and a negative
terminal and it is very important to
keep track of which is which on the
battery symbol the positive terminal is
indicated by the longer line and the
negative terminal by the shorter line
the plus and minus signs are not usually
drawn on the circuit so you must learn
to recognize which is which by looking
at the symbol a switch is a control
device if the switch is open as shown
here no current can flow if the switch
is closed the circuit is complete and
current can flow from the power source
to the load and back to the opposite
side of the power source
a fuse is a component that protects
other components if too much current is
flowing probably due to a malfunction in
the circuit or an attempt to connect too
many loads a fuse is designed to melt
creating an open circuit and this stops
the flow of current the resistor is a
type of load that usually is used to
limit the amount of current flowing in a
circuit resistors convert electrical
energy into heat energy
wires and other conductors are
represented with lines there is no way
to tell from the way the lines are drawn
whether the conductor is insulated or
not here are some additional symbols
that are commonly used to represent
various types of power sources on the
far left is a symbol for an AC voltage
source we will postpone consideration of
AC circuits until later in the course
next is the most common symbol used to
represent a battery as typically drawn
remember that the side of the symbol
with the longer line in this case at the
top is the positive terminal and the
side with the shorter line represents
the negative terminal to the right of
the battery symbol is a symbol
representing a generic DC voltage source
it could be a battery or it could be a
DC source derived electronically from an
AC power source such as a portable AC
power supply plugged into an outlet and
used to provide power to a laptop
computer or other electronic device last
on the far right is the symbol for a DC
current source physical devices that act
as current sources are derived from
voltage sources with some additional
components later we will see that when
analyzing circuit behavior it is
sometimes convenient to treat one or
more energy sources as if they were
current sources instead of voltage
sources