Transcript Document

Chp 18
Electricity
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What is Electricity?
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A form of energy
Used to make electrical
appliances work
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Electric Current

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It is the rate of flow
of electrical
charge.
The path that the
current flows
through is known
as a circuit.
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Electric Current
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Drawing circuit diagrams
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Battery
Switch
Light bulb
Resistor
Variable resistor/rheostat
Voltmeter
Ammeter
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Potential Difference:

The potential difference across any two
points is the amount of energy needed to
move one unit charge of electricity from
one point to the other.
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Resistance

Resistance of the object =
Potential difference across its ends
Current flowing through it
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Effects of an
Electric Current
Electrical energy can be transformed into other forms of energy to
produce many effects
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Heating Effect of a Current
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Wire heats up as a current passes through
it
Electrical energy is converted into heat
energy
Heat produced depends on the resistance
of the wire
Greater resistance, greater heat
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Heating Effect of a Current
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Heating appliances have coils of wires
made of high resistance materials such as
nichrome
Heating elements heat up when current
passes through them
Heat produced is then used for ironing,
toasting, cooking and drying
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Heating Elements in Heating
Appliance
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Heating Appliances
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Magnetic Effect of a Current
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An iron rod placed inside a coil of wire has
increased magnetic field when the current
is switched on
When the current is switched off, the iron
loses its magnetism
The set-up is known as an electromagnet
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Magnetic Effect of a Current
• Used in many applications
• Gives a magnetic field that can be switched on
and off when desired
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Applications of the Magnetic Effect
of Current
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Giant electromagnet
Telephone
Electric motors
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Chemical
Effect of a
Current
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Liquids such as salt water, vinegar and copper sulphate
solution allow electricity to pass through them
Liquids are known as electrolytes
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Chemical Effect of a Current
Electrolysis: Chemical decomposition of
an electrolyte by an electrical current
 Electrodes: Two wires or plates through
which current enters and leaves the
electrolyte
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Application of the Chemical
Effect of Current
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Electrolysis is used in electroplating
Flow of current causes a thin layer of metal
to be deposited on the object to be
electroplated
Electrolysis is also used in industries to
extract metals such as aluminium and
magnesium from their compounds
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Applications of Electroplating
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Lighting Effect of a Current
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Heating effect of a current can also lead to
the lighting effect
In a light bulb, the heat generated is so
great that the coiled filament begins to
glow and give out light
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Miscellaneous
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http://www.pge.com/microsi
te/PGE_dgz/wires/resist.ht
ml
http://www.bgfl.org/bgfl/cust
om/resources_ftp/client_ftp
/ks2/science/electricity_boo
k1/index.htm
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