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Static Electricity

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An electromagnet will continue to be a magnet as long as the current ... Producing Electric Energy Electricity & Magnetism Magnets and Magnetism An electric current ... – PowerPoint PPT presentation

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Title: Static Electricity


1
Static Electricity
  • Electricity Magnetism

2
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.

3
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.

4
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.

5
Static Electricity
  • Electrons sometimes jump between objects. When
    this happens we sometimes hear a crack and, in
    darkness, see a spark.

6
Producing Electric Energy
  • Electricity Magnetism

7
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.

8
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.

9
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.

10
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.

11
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.

12
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).

13
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.)

14
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15
Complete Circuits
  • Electricity Magnetism

16
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.

17
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.

18
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.

19
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.

20
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.

21
Series and Parallel Circuits
  • Electricity Magnetism

22
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.

23
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.

24
Series and Parallel Circuits
  • Various factors affect the resistance of a
    conductor
  • Type of material
  • Thickness of material
  • Length of material

25
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.

26
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.

27
Magnets and Magnetism
  • Electricity Magnetism

28
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.

29
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.

30
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.

31
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.

32
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.

33
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34
Electromagnets
  • Electricity Magnetism

35
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.

36
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.

37
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.

38
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

39
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.

40
Electromagnets
  • Electromagnets are used in many objects
  • Telephones
  • Telegraphs
  • Radios
  • Televisions
  • Motors
  • Doorbells
  • Electrical appliances
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