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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