Transcript Fancy Gizmo - Douglas County

Intro
• Size of electron and electron orbit in respect
to perceived matter.
• Force: electron and proton vs. gravity
• Tape, wool, balloon, paper punch holes,
graphite styrofoam balls
b
Warm up
• Given:
– a=3, b=3
– Find 
• Given:
– a=4, b=7
– Find 
• Given:
– a=5, b=8
– Find 
a

c
Electrostatics
Force and Charge
Charges
• Like charges repel
• Opposite charges attract
Like charges
• Each strip of clear tape has the same type
of charge when prepared in the same
manner (i.e. both positive or both negative)
– These strips of tape repel each other
Opposite charges
• When one strip is peeled from the roll and
one strip is peel from the desk, the charges
are opposite.
– These strips of tape attract each other.
Electrostatic related words
• Neutral
– Equal number of positive and negative charges
• Insulator
– Charge does not move easily through this
material (e.g. plastic or styrofoam)
• Conductor
– Charge moves easily through this material (e.g.
metals)
Electric Force
Force between two point sources
Electric force
• Two kinds of electric charges: positive and
negative
• Charges exert forces on other charges at a
distance (contact not required)
• The force decreases with distance
• Like charges repel; opposite charges attract.
Electroscope
• Charging by conduction: object come into
contact
• Charging by induction: object are in
proximity but never touch (requires
grounding)
• Examples
•
•
•
•
•
•
Wool
Monitor
Tape
Balloon
Van Degraff
Plastic
Example: electroscope
Charging by conduction
• A charge is created on an object.
• The object is brought into contact with
another object.
• The electrons transfer to even out the
distribution
Example: pans
Charging by induction
• Charge is created on an object.
• The object is brought near another object
(which is grounded).
• The charged object repels or attract
electrons on the grounded object.
• The grounded object transfers electrons to
or from the ground to reach equilibrium.
• If the ground is removed, the previously
grounded object will have an unbalanced
number of electrons and now be charged.
Example: styrofoam
Force and distance
• Force increases with charge
• Force decreases with distance
q A qB
FK 2
r
Proportional to the inverse square
• qA=10C, qB=10C
–
–
–
–
–
–
–
r=1mm
r=1.414mm
r=2mm
r=3mm
r=4mm
r=5mm
r=6mm
• Find the pattern
Pg 552 #11
q A qB
FK 2
r
N gm
K  9.0 x10
2
C
9
2
Homework
• Pg 557:
– Explain Key Concepts in your own words.
– Relate to your things you experience in real life.
• Ch 20 Study Guide
• Pg 558 #20-40
• Pg 559 #42-49, 51,59,60
Concepts section 1
Concepts section 2
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• Your Subtopics Go Here
Your Topic Goes Here
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TRANSITIONAL PAGE
elements
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