form 3 electricity part 1
TRANSCRIPT
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CHAPTER 7 : ELECTRICITY7.1 : Electrostatics7.2 : Electricity
7.3 : Measuring Electricity
7.4 : Ohms Law7.5 : Concept of Series & Parallel
Circuit 7.6 : Current, Voltage & Resistance in
a Series Circuit
7.7 : Current, Voltage & Resistance in a
Parallel Circuit 7.8 : Magnestism7.9 : Electromagnetism
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7.1 : ElectrostaticsStructure of an ATOM
Atom : thesmallest particlein an element
Has nucleus(proton +neutron) andelectrons
Differentelements have
different numberof electrons,protons andneutrons in theiratoms
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7.1 : ElectrostaticsProducing Static Electrical Charges
Electrostatic :The study ofstatic electricalcharges(+ve & -ve)
When 2 objectsare vigorouslyrubbed againsteach other, 1
object receiveselectrons & theother loseselectrons
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7.1 : ElectrostaticsProducing Static Electrical Charges
A charged objectattractsunchargedobjects
Objects with likecharges repeleach other
Objects withunlike chargesattract eachother
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7.1 : ElectrostaticsProducing Static Electrical Charges
Electroscope :To detectstaticelectricalcharges
Gold leaf of anunchargedelectroscopediverges
when achargedobject isbrought nearits metal cap
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7.1 : ElectrostaticsEveryday Phenomena Related to Static
Electrical Charges Lightning :
Due to static electrical charges in thethunderclouds escaping from cloud tocloud/ a cloud to the earth producing
bright flashesFriction between water molecules in the
clouds & the air molecules produces alarge quantity of electrical charges in the
cloudsLightning is produced when the electrical
charges in the clouds escape & producesbright flashes of light & loud sounds ofthunder
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7.1 : ElectrostaticsEveryday Phenomena Related to Static
Electrical Charges Lorry carrying petrol storage tank :
Lorry petrol tanker is in danger ofcatching fire because petrol flammable
As the lorry moves along a road, frictionbetween the lorry & air produceselectrical charges on the lorry
But the rubber tyres of the lorry preventthe charges from escaping to the earth
A metal chain attached to the lorrytouches the road so that electricalcharges are conducted by the metal chainto the ground
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7.1 : ElectrostaticsEveryday Phenomena Related to Static
Electrical Charges Car spark plugs :
Car spark plugsare use to ignitethe petrol
vapour in the
car engineWhen the car
engine starts,static electricalcharges jump
across the gapat the end of thespark plug,producingsparks to ignitethe fuel in the
engine
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7.1 : ElectrostaticsEveryday Phenomena Related to Static
Electrical Charges Aeroplane :
Aeroplane flyingthrough the airbuilds up static
electrical chargeon its body dueto friction withthe air
When aeroplanelands, its specialconductive tyresare able toconductelectricalcharges to the
ground
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7.1 : ElectrostaticsEveryday Phenomena Related to Static
Electrical Charges Photostat machine :
Rolling cylinderin the machinebecomes
charged withstatic electricalcharges & thepaper rolls out isalso charged
Charge paperattracts carbonpowder to it toproduce a copyof the originaldocument
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7.1 : ElectrostaticsEveryday Phenomena Related to Static
Electrical Charges Dry hair :
Dry hair stands upwhen it isvigorously combed
on a dry day
When the hair iscombed, frictionbetween the hair &the comb produces
static electricalcharges As the hair has like
charges, the strandsof hair repel one
another & stand
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7.1 : ElectrostaticsSafety measures for Electrical Charges
Care must be takenwhen dealing withelectrical charges forthey can injure/kill/damage
Examples :
Tall buildings
installed withlightning conductorsto prevent thebuildings from being
damaged by lightning
People living onmountains should notuse zinc sheets asthey attract lightning