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Magnetism and Electromagnetism


Magnetism and Electromagnetism. Chapter 19. Chapter 19. The Nature of Magnetism. magnetism - the force of attraction or repulsion of magnetic materials ... – PowerPoint PPT presentation

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Title: Magnetism and Electromagnetism

Magnetism and Electromagnetism
  • Chapter 19

The Nature of Magnetism
  • magnetism - the force of attraction or repulsion
    of magnetic materials
  • magnetic pole - the ends of a magnetic object,
    where the magnetic force is strongest.
  • North and south poles
  • Magnetic poles that are alike repel each other
    and magnetic poles that are unlike attract each
  • What happens when you break a magnet?

Magnetic Field
  • The region around a magnet where the magnetic
    force is exerted
  • magnetic field lines - Diagram pg.615
  • magnetic field interactions - Diagram pg.616

  • In a magnetized material, all or most of the
    domains are arranged in the same direction pg.617
  • making magnets - metallic object in a strong
    magnetic field, or rub it with a strong magnet
  • destroying magnets - drop it or strike it, heat
    it up

Magnetic Earth
  • compass - a device with a magnetized needle that
    can spin freely
  • Earth has an immense magnetic field surrounding
    it, just as there is a magnetic field around a
    bar magnet
  • magnetic declination - the angle between
    geographic north and the north to which a compass
    needle points pg. 624

Magnetic Earth (cont.)
  • Earths magnetic field affects the movements of
    electrically charged particles in space. Charged
    particles also affect the Earths magnetic field.
  • Molten rocks that harden can also indicate the
    direction of the earths magnetic field at the
    time the rocks cooled

Electric Current and Magnetic Fields
  • electric charge - a property of electrons and
  • electrons carry a negative charge
  • protons carry a positive charge
  • electric current - the flow of a charge through a
  • an electric current produces a magnetic field

Electric circuit
  • A complete path though which electric charges can
  • Circuit must have
  • 1) source of electrical energy,
  • 2) devices run by electrical energy,
  • 3) conducting wires and a switch

  • conductor - electric currents move freely
  • insulator - electric current does not flow
    easily, electrons bound tightly to their atoms
  • resistance - the opposition to the movement of
    electrical charges flowing through a material
  • superconductors - material that has no electrical

  • solenoid - a current carrying coil of wire with
    many loops that acts as a magnet
  • electromagnet - a solenoid with a ferromagnetic
    core that forms a magnet that can be turned on
    and off
  • increasing strength of electromagnet - increase
    current, increase number of loops of wire
  • recorders - vibrations of voice are changed into
    electric current, recorded as change in magnetic
    field. Create magnetic pattern.