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Chp 18 Electricity

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What is Electricity?

A form of energy Used to make electrical

appliances work

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Electric Current

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 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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Electrical energy can be transformed into other forms of energy to produce many effects

Effects of an Electric Current

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Heating Effect of a Current

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

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

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

Giant electromagnet Telephone Electric motors

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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

Chemical Effect of a Current

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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

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

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

http://www.pge.com/microsite/PGE_dgz/wires/resist.html

http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks2/science/electricity_book1/index.htm