Lesson 11 Forces and Electrical Charges

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• Chapter 1
• Lesson 1-1 Forces and Electrical Charges

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Thales

• Greek who lived around 600 B.C.E.
• One of the first to describe phenomenon related
  to electricity
• Described what happened when rubbed a piece of
  amber with wool

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William Gilbert

• English scientist repeated Thales experiment in
  1570
• Named the effects electricity
• Electricity comes form the Greek word for amber,
  elektron

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Thales and Gilbert

• Discovered electricity is everywhere

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Electric Energy Energy ability to do work or
cause changes

• stove converts electric energy into heat energy
  that cooks food
• light bulb converts electric energy into light
  and heat energy

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Electric Charge

• Electrical charge is a force within the particle.
  
• Basic property of matter
• All matter is made up of atoms.

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Atoms

• Everything in the universe is made of atoms

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• The human body is made of atoms.
• Air and water are, too.
• Atoms are the building blocks of the universe.

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• If you could see an atom, it would look a little
  like a tiny center of balls surrounded by giant
  invisible shells.

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• Atoms are so small that millions of them would
  fit on the head of a pin.

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• Atoms are made of even smaller particles. The
  center of an atom is called the nucleus. It is
  made of particles called protons and neutrons.

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• The protons and neutrons are very small, but
  electrons are much, much smaller.

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• Electrons spin around the nucleus in shells a
  great distance from the nucleus.

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• If the nucleus were the size of a tennis ball,
  the atom would be the size of the Empire State
  Building. Atoms are mostly empty space.

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Protons, Electrons, Neutrons

• Protons - have a positive charge ()
• Electrons - have a negative charge (-)
• Neutrons - carry no charge
• number of neutrons can vary

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Electrical Charge

• Concentration of electric charges

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Law of Electric ChargeLike Charges Repel

• Objects that have the same charge repel each
  other
• Object exerts a force on the other object
• Forces push objects apart

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Law of Electric Charge Opposite Charges Attract

• Objects that have opposite charges are attracted
  to each other
• Object exerts a force on the other object
• Forces pull the objects together

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Static Charge

• Electrically neutral
• equal number of protons and electrons
• Static Charge
• Object has a positive or negative charge
• Neutral objects gains electrons, negatively
  charge
• Neutral objects loses electrons, positively charge

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Static Electricity

• Buildup of charge on an object
• Most static charges trillions times larger than
  charge of single electron or proton
• Examples
• Shock from touching doorknob after walking on
  carpet
• Lightning

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Comb and Paper Experiment

• Effect of static electricity when small pieces of
  paper were attracted to plastic comb after comb
  was rubbed with wool

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THREE WAYS TO CHARGE AN OBJECT
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FRICTION
CONDUCTION
INDUCTION
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FRICTION

• Objects can be charged by rubbing them together
• when two neutral objects rub together, electrons
  are transferred from one object to the other
• Example
• Static Cling as clothes tumble together in
  dryer some become positively charged and others
  negatively charged

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• Charging by friction
• Gives two neutral materials opposite charges when
  rubbed together
• NO NEW CHARGES ARE CREATED
• Existing charges move to other objects or to new
  areas on the same object

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FRICTION - DEMONSTRATION

• Rubber rod that is rubbed against a piece of wool
• Electrons move from the wool to the rod
• Rod becomes negatively charged
• Wool becomes positively charged

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FRICTION - DEMONSTRATION

• Rubbing a balloon on your hair
• electrons move from hair to the balloon
• balloon becomes negatively charged
• hair becomes positively charged

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Conduction

• Neutral objects can be charged by coming into
  contact with an already charged object
• when a charged object touches a neutral object,
  electrons are transferred to the neutral object
• objects that are charged by conduction have the
  same charge as the object that was used to charge
  them

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• Charging by conduction
• Happens when electrons move from one object to
  another by direct contact
• NO NEW CHARGES ARE CREATED

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CONDUCTION - DEMONSTRATION

• Touch a negatively charged rubber rod to a pile
  of neutral paper confetti
• confetti quickly flies apart
• pieces of confetti gain electrons and become
  negatively charged
• like charges repel

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CONDUCTION - DEMONSTRATION

• A positively charged glass rod touches an
  uncharged metal rod
• electrons from the metal rod move to the glass
  rod
• the metal rod looses electrons and becomes
  positively charged

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Induction

• Charged object is brought close to a neutral
  conductor, electrons in the neutral conductor can
  move to the new positions
• A material has areas of both negative and
  positive charges
• Causes an object to have a charge that is
  opposite to the charge that is brought near it

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• Charging by induction
• Happens when charges in an uncharged object are
  rearranged without direct contact with a charged
  object

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INDUCTION - DEMONSTRATION

• Rub a balloon against someones hair, charging
  the balloon by friction. The balloon becomes
  negatively charged. Hold the balloon near a
  neutral wall and let go.
• negative charge of the balloon induces a region
  of positive charge on the wall

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MISCONCEPTION ALERT!!!!!!

• MISCONCEPTION atoms can gain or lose protons as
  well as electrons
• TRUTH
• atoms can only lose or gain electrons, which are
  negatively charged
• A net loss of electrons leaves an atom positively
  charges
• A net gain of electrons leaves and atom
  negatively charged

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Conservation of Charge

• When you charge something by any method, no
  charges are created or destroyed
• The numbers of electrons and protons stay the
  same
• Electrons simply move from one atom to another
• Charges are neither created or destroyed, they
  are conserved

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Bibliography

• Aldridge, Bill, Jack Ballinger, and Albert
  Kaskel. Science Interactions Course 3. 3rd ed.
  New York, New York Glencoe, 1995. 20-26.
• Becker, Joseph. "Electricity and Magnetism." San
  José State University. 2006. San José State
  University. 14 July 2008 lthttp//www.physics.sjsu
  .edu/becker/physics51/elec_charge.htmgt.
• Champagne, Andrew. Electricity and Magnetism.
  Austin Holt, Rinehart and Winston, 2005. 2-10.
• "Energy Kids Page." USA Government Department of
  Energy. Nov. 2007. 14 July 2008http//www.eia.doe
  .gov/kids/energyfacts/sources /electricity.html.
  
• Maineri, Sarah, and Jeanette Wall. Electrical
  Connections. Nashua Delta Science, 2007. 2-6.
• Radar, Andrew. Chem4Kids. 2007. Andrew Rader
  Studios. 14 July 2008 lthttp//www.chem4kids.com/f
  iles/atom_structure.htmlgt.