Static Electricity

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Static Electricity

• Electricity Magnetism

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Static Electricity

• Matter is composed of small particles called
  atoms.
• The atom is composed of protons, neutrons, and
  electrons.
• Normally, atoms are neutral (no charge) because
  they have the same number of protons as
  electrons.
• Some substances can gain and lose electrons
  easily because of their properties.

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Static Electricity

• When a balloon is rubbed with a wool cloth
  (friction), the wool cloth loses some of its
  electrons.
• Because the wool cloth now has more protons than
  electrons, it is positively charged.
• The balloon has gained electrons and is,
  therefore, negatively charged.

• By bringing the negatively charged balloon into
  contact with positively charged items, they
  become attracted.

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Law of Electrostatics

• This is an example of one of the basic Laws of
  Electrostatics Unlike charges attract each
  other.
• It also states that like charges repel.
• Example If two negatively charged balloons are
  brought near each other, they repel each other.

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Static Electricity

• Electrons sometimes jump between objects. When
  this happens we sometimes hear a crack and, in
  darkness, see a spark.

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Producing Electric Energy

• Electricity Magnetism

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Magnets and Magnetism

• An electric current flows when electrons move
  from atom to atom through a conductor.
• In 1820, Hans Oerstead, a Danish physicist,
  discovered that electric current passing through
  a wire produces a magnetic field around the wire.
• If the wire is coiled around an iron ore an
  electromagnet is produced.

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Producing Electric Energy

• Other methods of generating electric current have
  been found, such as with chemical energy.
• The wet cell, a battery, consists of a copper
  strip (positive electrode) and a zinc strip
  (negative electrode) in a diluted acid solution.
• The acid solution, known as an electrolyte, is
  capable of conducting an electrical current.

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Producing Electric Energy

• Electrons leave the copper strip, giving it a
  positive charge. As the zinc dissolves, it has
  surplus electrons, giving it a negative charge.
• Electrons flow from the zinc strip through the
  conductor to the copper strip.
• The electrical current produced from the flow of
  electrons can cause a bulb to light.

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Producing Electric Energy

• The current produced is called direct current
  (D.C.).
• Heat energy can also be used to generate an
  electrical current.
• When set of dissimilar metal strips (called
  thermopiles) are heated, an electric current is
  generated that flows through the connecting wires.

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Producing Electric Energy

• An instrument called the ammeter measures
  electric current.
• Sunlight can also be used to produce electricity.
• Solar cells consist of semiconductors made of
  silicon crystals.
• The suns energy can cause electrons to flow
  between the semiconductors, producing a small
  current.

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Producing Electric Energy

• A power plant generator consists of
  electromagnets that are made to spin within an
  armature, which consists of many coils of wire.
• The process begins with a turbine, which will
  turn from the force of wind, moving water, or
  heated water (steam).

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Producing Electric Energy

• At the spinning of the turbine and shaft cause
  electromagnets to spin within the armature.
• This current is used to supply the electromagnets
  and to supply electrical energy for consumers.
• The current generated is called alternating
  current (A.C.)

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Complete Circuits

• Electricity Magnetism

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Complete Circuits

• The electrical energy produced by a generator or
  battery can be made to follow certain paths.
• The flow of electrical energy is called an
  electrical current.
• The electrons flow in a metal conductor, such as
  copper wire, is from the negative to positive
  pole.

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Complete Circuits

• The path taken by the electrical current is known
  as a circuit.
• When the pathway is unbroken and the current
  flows from the source through the conductor and
  back again, the circuit is said to be complete.

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Complete Circuits

• When someone flips on a light switch, the circuit
  is complete and electrical current flows through
  the light bulb, producing light.
• When someone pushes a doorbell button the circuit
  is complete and the bell rings.
• The complete circuit is also called a closed
  circuit because there is no opening or break in
  the path of electron flow.

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Complete Circuits

• A switch allows one to control the flow of
  electrical current.
• When the switch is open, or in the off position,
  the current cannot flow through the conductors.
• This is called an open circuit.

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Complete Circuits

• If the electric current completes a circuit
  without servicing the device it was intended to
  operate, as when two bare conductor wires come in
  contact with each other, a short circuit
  results.
• This causes the wire to heat up without operating
  the electrical device.

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Series and Parallel Circuits

• Electricity Magnetism

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Series and Parallel Circuits

• Electrical current can be measured in several
  ways.
• Electrons flow through a conductor when there is
  a surplus of electrons at one pole and a deficit
  at the other pole.
• The electrical potential of the two poles is
  different. This difference is known as the
  electromotive force (EMF), or voltage.

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Series and Parallel Circuits

• The instrument used to measure voltage is the
  voltmeter.
• The rate of flow of the electrical current is
  measured in units called amperes (amps).
• The ammeter is the instrument used to measure
  amperage.
• As the electrons move through the conductor, a
  certain amount of opposition is known as
  resistance and is measured in units called ohms.

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Series and Parallel Circuits

• Various factors affect the resistance of a
  conductor
• Type of material
• Thickness of material
• Length of material

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Series and Parallel Circuits

• A complete circuit can be set up in two ways, a
  series or parallel circuit.
• In the series circuit the electrons have only one
  path through which they may flow.
• When two bulbs are connected in series with one
  dry cell, the ammeter shows that the strength of
  the current is less when compared to a one bulb
  circuit because the second bulb acts as a
  resistor.

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Series and Parallel Circuits

• When two bulbs are connected in parallel with one
  dry cell, the ammeter indicates greater amperage
  compared to the one bulb circuit.
• This is because the current has more than one
  path to follow so there is less resistance.

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Magnets and Magnetism

• Electricity Magnetism

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Magnets and Magnetism

• Magnetic iron ore was discovered by the Greeks in
  a region once known as Magnesia.
• Natural magnets, called lodestones, are composed
  of the mineral magnetite.
• Certain materials such as iron (steel), nickel,
  and cobalt are attracted to magnets and can be
  formed into magnets of various shapes.

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Magnets and Magnetism

• The domain theory of magnetism is based on the
  concept of the magnetic field of individual
  atoms.
• Certain elements, such as iron, can become
  aligned.
• The aligned clusters of atoms then form magnetic
  domains within pieces of iron.

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Magnets and Magnetism

• The attraction or repulsion is strongest at the
  ends, called poles.
• One end is the north seeking pole (N) and the
  other is the south seeking pole (S).
• When like poles are brought together they repel
  each other, unlike poles attract each other.

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Magnets and Magnetism

• The magnetic field in the space around a magnet
  is defined by the lines of force.
• The patterns of these invisible lines of force
  can be seen when iron filings are sprinkled
  around a magnet.

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Magnets and Magnetism

• The earth behaves as a huge magnet and therefore
  has magnetic lines of force.
• It is these lines of force that align the north
  end of a directional compass needle to the
  magnetic north pole of the earth.

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Electromagnets

• Electricity Magnetism

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Magnets and Magnetism

• In an unmagnetized piece of iron the domains are
  randomly oriented.
• However, if the piece of iron is placed next to a
  strong magnet, many of the domains will arrange
  themselves in line with the magnetic field.

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Electromagnets

• Electromagnets have three requirements
• Electric current
• Coiled, insulated wire
• A soft iron bar
• When a current flows through the coiled wire
  wrapped around the bar (core), the bar and coiled
  wire act like a magnet.
• They can pick up objects and they have north and
  south seeking poles.

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Electromagnets

• For electromagnets, a soft iron bar is used
  because it magnetizes easily and also loses its
  magnetism easily.
• An electromagnet will continue to be a magnet as
  long as the current flows through the coiled
  wire.
• For this reason, electromagnets are called
  temporary magnets.

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Electromagnets

• When a current flows through a wire, a magnetic
  field (lines of force) occurs.
• In an electromagnet the lines of force occur
  around the soft iron core and coiled wire.
• The electric force of an electromagnet can be
  made stronger in two ways
• By increasing the number of turns of coiled wire
  around the core
• And/or by increasing the amount of electric
  current

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Electromagnets

• Doubling the number of turns of wire or doubling
  the electric current will double the magnetic
  force of the electromagnet.
• The poles of the electromagnet can be reversed by
  reversing the wire connection at the source of
  electricity.
• Pole designation may be determined by using a
  compass.

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Electromagnets

• Electromagnets are used in many objects
• Telephones
• Telegraphs
• Radios
• Televisions
• Motors
• Doorbells
• Electrical appliances