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Electrical Charges
Objectives:
Demonstrate that there are two typesof electric charges (after doingexperiments & documentary
research)
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All matter has electrical charges
There are two types of charges:
Positive
Negative
If you have an equal number ofpositives as negatives, makesneutral
Electrical Charges:
+
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http://www.youtube.com/watch?v=LkIai_KXGxghttp://www.youtube.com/watch?v=LkIai_KXGxg -
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There are 2 forces between chargedobjects:
Attraction Repulsion
Opposite charges
Opposites Attract
Same charges
Like repel
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Sphere A is negatively charged.
A
When placed beside sphere B, they attract.
What is the charge on B?
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B
A
+
OppositesAttract!
POSITIVE
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Three charged spheres are suspendednext to each other.
A B B C
If sphere A isnegativelycharged,
what will happen when sphere A & C aresuspended beside each other?
A C
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Attract
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Four charged spheres are suspendednext to each other.
A B B C C D
What will happen if A & D were suspendednext to each other?
+ + + - - +
Repel
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You have three chargedobjects A, B & C in a lab.You record the following
results:Test Observation
Bring A near B They repel
Bring A near C They attract
What would happen if B & Cwere brought together?
They would attract!!!
+ +
+ -+ -
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Electrostatic:
All objects begin neutral& canbecome positivelyor negativelycharged
A positivelycharged object has morepositives than negatives
A negativelycharged object has morenegatives than positives
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Electrostatic seriesis a list that ranksobjects ability to take negative charges
Electrostatic Series:
Rubber
Ebonite
Polyethylene
Cotton
SilkWoolGlass
Acetate
Fur / Hair
Items at toptakenegatives
Items at bottomlosenegatives
Only negativecharges move!Positive charges NEVERmove!!
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Rubber Ebonite Polyethylene
CottonSilk
Wool
Glass
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Your cat rubs against a rubber balloon.What will be the charge on the balloon?Your cats fur?
RubberEbonitePolyethyleneCotton
SilkWoolGlassAcetate
Fur / Hair
Rubber
Fur / Hair
Items at toptakenegatives
Negatives
Rubberballoon
becomesnegative
Cats furbecomespositive
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In a lab, you take a piece of neutral wool& neutral polyethylene & rub themtogether. What will be their charges?
RubberEbonitePolyethyleneCotton
SilkWoolGlassAcetate
Fur / Hair
Wool
Polyethylene
Items at toptakenegatives
Negatives
Polyethyleneballoon
becomesnegative
Woolbecomespositive
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In a lab, you rub a piece ofcotton & ebonite together.Then you rub a piece of silk
& glass together.
RubberEbonitePolyethylene
CottonSilkWoolGlass
AcetateFur / Hair
Cotton is +
Silk is -Theywould
ATTRACT
You then bring the charged piece ofcotton& the charged piece ofsilk
together. What will happen?
+
-
-+
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You rub your hair with a balloon.Explain using words & pictures,why your hair sticks up.
1st Hair & balloon areboth neutral
2nd Rubber balloon takesnegative charges from thehair. So, balloonbecomesnegativelycharged & hairbecomes positivelycharged
3rd Since hair is positive &like charges repel,
hair sticks up!!!
+
+
++
+
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Two types of charges positive(+) &negative (-)
Opposites Attract
Like Repel
Items at thetopof the electrostaticseries list take negative charges
Only negativecharges move
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Activities
Worksheet #1