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Drawing circuit diagrams
• You must have
– Straight lines
– Sharp corners
– Use the correct symbols
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Circuit symbols
Light
bulb
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Can you remember….?
Component
Battery
Wire
Bulb
Buzzer
Symbol
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Which light bulbs will light?
A
B
C
D
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A complete circuit
For electricity to flow in a circuit it
must be able to flow from one end of
the battery to the other end
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Electricity does not only flow inside
wires!
• Lots of materials let electricity flow through
them.
• An electrical conductor allows electricity to
flow through it.
• An electrical insulator does not allow
electricity to flow through it.
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Testing to see if a material is an electrical conductor or
an insulator
Set up the circuit shown and place different materials in the gap in the
circuit. Record which materials let electricity through (the bulb lights if
electricity flows).
What do we call a material that lets electricity flow through it? CONDUCTOR
What do we call a material that does not let electricity flow
through it?
INSULATOR
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Electron Flow
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Electron flow
Electricity in wires is a flow of electrons along the wire
from the negative end of the battery to the positive end
What do we call this flow of electrons? Electrical current
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Voltage
oltage is a measure of how big a push
The v_____
lectrons are given as they leave the
the e_______
attery The bigger the voltage, the bigger
b_____.
ush
the p___.
lamps
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Measuring voltage
The unit of measure for voltage is the volt, symbol V.
Voltage is measured using an voltmeter. .
V
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Current
ircuit current is the flow of
In an electric c____,
lectrons carrying electrical energy. The
e_______
bigger the current, the m___
ore electrons are
flowing around the circuit.
lamps
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Measuring current
The unit of measure for current is the amp, symbol A.
Current is measured using an ammeter.
A
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Set up the two circuits shown:
A.
BRIGHTER
B.
DIMMER
What
do
happens
The
Series
we
Parallel
In circuit
call
other
ifare
Circuit
circuit
you
Circuit
circuit
Athe
bulb
the
unscrew
B?
A?
bulbs
staysthe
goes
out.
lit.
are
a
one
bulb
the
bulb
inbrightest.
circuit
in Circuit
B? A?
In
which
circuit
bulbs
brightest?
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A series circuit
• All bulbs will glow dimmer!
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Old Christmas tree lights
• If one bulb breaks the circuit is broken - all
bulbs go out!
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A Parallel circuit
• The bulbs all glow brightly!
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Example:In new christmas tree lights
• If one bulb is broken the other bulbs can still
light
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Think
• How do you think lights on a xmas tree are set
up?
• What about street lamps?
• Lights in a car?
• Lights in your house – between rooms?
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Series circuit – 1 bulb
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Series circuit – 2 bulbs
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Parallel Circuit
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Resistance
Resistance is how much a material tries to stop
electricity passing through it!!!
The symbol = R
Measured in Ohms .using an Ohmmeter.
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Experiment:
How are current and voltage related as electricity flows
through resistor?
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The two quantities current and
voltage are directly
proportional.
x
x
x
x
x
The graph of current against
voltage is a straight line
Current / A
Current-voltage graph for a resistor
x
x
x
Voltage/ A
Ohm’s Law
The voltage and the current in a circuit are directly
proportional to each other when resistance and
temperature are constant
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Resistance
Resistance
Calculating resistance
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Ohms law triangle
Whatever you are trying to find cover it up and it will
leave you with the calculation that you need.
So if you are
trying to find
current (I)...
…cover up I…
…which gives
the formula…

V
I

R
V
I =
R
x
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A bulb has a current of
20 A and a voltage of
100 V
What is the resistance?
R = V
I
= 100 V
20 A
= 5
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The everyday uses of electricity
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1. The heating effect of an electric
current
• Applications: irons, kettles etc
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The magnetic effect of an electrical
current
• Application : electric motor.
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The chemical effect of an electrical
current
•An electrical current can cause
chemical reactions to happen!
• Application: when
electricity is passed
through water it
breaks up into oxygen
and hydrogen gas!
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Hydrogen gas can then be used as a
fuel
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Simple Circuits
1. A complete circuit is required for
electric current to flow
2. Circuits can be drawn using circuit
diagrams with correct symbols
3. Components can be arranged in series
or parallel
Circuit Symbols
Switches - series circuit
Switches - parallel circuit
Drag & Drop Circuit
What is this a symbol for?
Bulb
Switch
Battery
Wire
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What is this a symbol for?
Bulb
Switch
Battery
Wire
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What is this a symbol for?
Bulb
Switch
Battery
Wire
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What is this a symbol for?
Bulb
Switch
Battery
Wire
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What is this a symbol for?
Bulb
Switch
Battery
Wire
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What is the name of the
tiny particles that move
through circuits?
Atoms
Currants
Electrodes
Electrons
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What is the name of the
tiny particles that move
through circuits?
Atoms
Currants
Electrodes
Electrons
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What is the name of
something that lets
electricity pass through?
Conductor
Insulator
Substance
Controller
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What is the name of
something that lets
electricity pass through?
Conductor
Insulator
Substance
Controller
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What is the name of
something that does not let
electricity pass through?
Indicator
Alligator
Terminator
Insulator
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What is the name of
something that does not let
electricity pass through?
Indicator
Alligator
Terminator
Insulator
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What kind of circuit are the
bulbs in?
Parallel
Serious
Series
Parrot
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What kind of circuit are the
bulbs in?
Parallel
Serious
Series
Parrot
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What kind of circuit are the
bulbs in?
Parallel
Serious
Series
Parrot
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What kind of circuit are the
bulbs in?
Parallel
Serious
Series
Parrot
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What is the name of the
thing shown below?
Very interesting
Very stupid
Variable resistor
Variable bulb
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What is the name of the
thing shown below?
Very interesting
Very stupid
Variable resistor
Variable bulb
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