static electricity i: particle model of electricity
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STATIC ELECTRICITY I:Particle Model of Electricity
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S1-3-04 Relate the particle model of electricity to atomic structure.
KEY WORDSNeutral Conservation of ChargeInsulator ConductorPolarization
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Electrostatics:Study of static electricity – static means “at rest.”• Electricity that is localized, not moving
Greek Philosophers noted: Amber rubbed with fur attracts bits of paper / dust.
Electric, electricity and electron all come from the
Greek word for amber - elektron
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Benjamin Franklin (1750)
• Experimented with friction; causes objects to repel or attract materials – “charged”
First to use words “positive” and “negative” as description
Atoms (and subatomic particles) were not discovered yet – try explaining electricity without electrons…?
• Knew electric charge came from a transfer of invisible SOMETHING
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Atoms contain 3 subatomic particles (1890)• Neutron – stationary particle with no charge (nucleus)
• Proton – stationary particle with a positive charge (nucleus)
• Electron – moving particle with a negative charge (orbits)
Friction (rubbing) provides enough energy to cause electrons to transfer between materials
We now KNOW:
• All atoms start off neutral: no net electric charge
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Negative and positive static charges result from the addition and removal of
electrons ONLY
(-) (+)
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Particle model of Electricity
• Three states of charge exist : (+) and (-) and neutral
• Neutral objects are charged by friction (displacing electrons)
“triboelectric charging”
• Charges create forces of attraction and repulsion
Remember :Since no new particles are created (Conservation of Matter)
the number of (+)/(-) stay the same (Conservation of Charge)
(+) and (-) (-) and (-) OR (+) and (+)
• Static is stationary electric charge built up on a material
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Notice the Conservation of Charge – after the transfer of electrons the net charge (together) still adds to zero
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Most Positive (+)Human Skin
+++
+
FurGlass
Human HairWoolSilk
Paper
Cotton Rubber -
- - -
CopperSilver
Polyester
Plastic
Most Negative (-)
When rubbed together, materials have a different strength of attraction for the electrons
Easily lose electrons
Easily gain electrons
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Since static electricity is stationary charge (stays put) only some materials can maintain a charge
Insulators:Electrical charge is localized - fixedElectrons can’t move around
Rubber, plastic, cloth, glass, wood
Conductors: Electrical charge spreads through material Electrons move around, weakening charge
Most metals are good conductors
Consider which balloon you can charge by rubbing on your hair and have stick to a wall
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Charged objects attract a neutral object by inducing electrons to move over to one side:
Polarization – separation of charges within a material creating (+) and (-) areas
Electrons repel – polarization of paper atoms
Causes Attraction!
(-) charged object
Neutral object
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+++++
++
Electrons attract – polarization of paper atoms
Causes Attraction!
(+) charged object
Neutral object
This separation of charges explains why neutral objects attract to both
(+) and (-) charged objects
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Lightning is (-) charge in the clouds causing polarization in
the surface of the Earth followed by a shock of
electrons between the two
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CAN YOU ANSWER THESE QUESTIONS?S1-3-04:How does the Atomic Model help to explain static electricity?
KEY WORDSNeutral Conservation of ChargeInsulator ConductorPolarization