Let’s Summarize
Chapter 9
Electricity and circuits
Vocabulary
What is an Electric circuit?
Cell, Current, Conductor,
Electron, Insulator, Series
circuit, Parallel circuit, Ammeter,
Ampere
An electric circuit is a closed path along
which electrons can flow from and return to
an energy source (ex. battery or cell)
REMEMBER
The tiny particles which carry
electric charges round the
circuits are called as
ELECTRONS.
SIMPLE ELECTRIC DIAGRAM
CLOSED CIRCUIT
A closed circuit is a complete
electric circuit that allows electrons
to flow along an uninterrupted path
OPEN CIRCUIT
Electrons do not flow through any part
of a circuit where there is a gap or
break.
An open circuit is one in which there is
an opening that does not allow current
to flow.
CURRENT FLOW IN CIRCUIT
The unidirectional flow of
charged particles (electrons) in
a substance (electrical
conductors) is called an
Electric current.
The electron charge flow from
negative (-) side to positive
(+) side.
How much current
is flowing in a
circuit can be
measure in
Amperes (Amps)
The more charge
that flows, the
bigger the current.
Amperes are measured
with an instrument
called an ammeter
CONDUCTORS
A conductor, or electrical
conductor, is a substance or
material that allows
electricity to flow through it.
The ampere is named after
the French physicist
André Ampѐre who lived
from 1775 - 1836
INSULATORS
Materials that do not allow
electricity to flow through
them are called electrical
insulators or simply insulators.
CIRCUIT SYMBOLS
• Engineers and designers of
electrical circuits use
special symbols that show
components and
connections in a circuit.
• These symbols make it
easier to plan and analyze a
circuit before you build it.
• A drawing made with these
symbols is called a circuit
diagram
SERIES CIRCUIT
A closed circuit is a complete electric circuit that allows
electrons to flow along an uninterrupted path.
 The amount of current is same in all parts of a series
circuit.
 However, if you add more resistors, you increase the
total resistance of the circuit.
For example, adding an
extra bulb to a series of
lights makes all of the
bulbs dimmer.
PARALLEL CIRCUIT
In parallel circuit each component has its own
path of current.
The points where a circuit divides into different
paths are called junction points.
Adding a new
pathway with
more resistors
does not affect
the resistance of
any of the other
pathway.
Infact, adding
extra resistors in
parallel decrease
the total
resistance of the
circuit.
The lamps in parallel circuit will be brighter than those in
series circuit.

Because in series circuit electricity is shared by the lamps equally, so each lamp
gets a share of the electricity from the cell.

A series circuit is a Voltage Divider. Two light bulbs on the same series circuit
share the voltage of the battery: if the battery is 9V, then each bulb gets 4.5 volts.

Were as in parallel circuit, the same amount of electricity passes through each
lamp from the cell.

A parallel circuit avoids the voltage distribution problem. Two bulbs in a simple
parallel circuit each enjoy the full voltage of the battery. This is why the bulbs in
the parallel circuit will be brighter than those in the series circuit.