Science Form 3 Electricity
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Transcript of Science Form 3 Electricity
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Electricity
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Electricity
Electrical energy produced
when electric current flows.
A source of electrical energy isany device that produced
electrical energy.
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Sources of electrical energy
Chemical cell
Biomass fuel
Solar cell
Geothermal
energy
Hydroelectricpower
Wind energy
Tidal energy
Fossil fuel
Nuclear
energy
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Electric current
2 types of electricity :
a) electrical charges (electrostatic)
b) electrical current
Electric current is produced when
there is a flow of negative charges
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Electric current : from positive to negative
Electron : from negative to positive
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Electric Current
Rate of flow of negative charges
in a circuit
Unit : ampere (A) Measuring device : ammeter
To measure current, ammeter
must be connected in series, in acircuit.
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Voltage
The force that is needed to make
charges flow from one point to
another in a conductor Unit : voltage (V)
Measuring device : voltmeter
To measure voltage, voltmetermust be connected in parallel,
in a circuit.
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Resistance
The property of a substances that
opposes the flow of electric
current A substance with very high
resistance only allows a small
current to flow through it. Unit : ohm ()
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Resistance
Depends on :
a) diameter/ thickness of conductor
Big , small
b) length of conductor
long , shortc) type of conductor
tungsten , copper
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Symbols
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Voltage, current andresistance in a series circuit
Total current
I = I1 =I2 = I3
Total voltage
V = V1 +V2 + V3 Total resistance
R = R1 +R2 + R3
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Series circuit
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Series circuit
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Series circuit
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Voltage, current andresistance in a parallel circuit
Total current
I = I1 +I2 + I3
Total voltage
V = V1 =V2 = V3
Total resistance1/R = 1/R
1+
1/R
2+ 1/R
3
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Parallel circuit
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Parallel circuit
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Parallel circuit
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The differences
Series
One
Other bulbsdo not light
up
Method ofconnection
Number ofpathway
Condition ifone bulbs is
removed /fused
Parallel
More than
one
Other bulbsremainlighted