Magnetism and Uses

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Magnetism and Uses

• Goals magnetism, source, types,
  electromagnetism, magnetic materials, force
  calculations, motors, generators and transformers

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Magnetism

• Magnetism field force with north and south
  poles
• Alignment of magnetic domains
• Domains- groups of atoms with magnetic fields
  that complement one another
• Atoms exhibit magnetic properties because of the
  spin of an unpaired electron (moving electric
  field) (fourth quantum number)
• Opposite poles attract and the same poles repel
• Field lines point away from North and toward the
  South pole

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Types of Magnets

• Permanent and an Electromagnet
• Permanent hold magnetic properties domains
  are aligned bar and horseshoe
• Magnetized in an electric current or a strong
  magnetic field
• Unmagnetized by shock, heat or another field
• Diamagnetic- fields cancel no magnetism Pb
• Paramagnetic- atoms are magnetic but not domains
  Al

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• Nonmagnetic- when permanent magnet is removed
  there is no magnetism
• Ferromagnetic strong magnetic properties Fe
  Ni Co Nd
• Earth and Stars
• Electromagnets coil with an iron core
• Advantages turned on and off and vary the
  magnetic strength (lab)
• Turns in the coil current size of core
• Why? Current - carrying conductor has a
  magnetic field around it Right Hand Rule
• Oersteds discovery- with a compass and current
  discovered that the current produced a magnetic
  field reversed by reversing the current
  direction

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Electromagnetism

• Magnetism produces electricity and electricity
  produces magnetism
• Faraday law of induction
• Electric motors and Generators
• Home wiring AC , current in opposite
  directions repel magnetic fields in the same
  direction attract
• Motors electrical to mechanical energy
• Electromagnet in the core of the motor is pushed
  by the field of the electromagnet continually as
  the magnetic field is reversed easier in AC
• Parts include armature (moving electromagnet),
  rotor, brushes, permanent magnet and commutator
  (switch) (Lab)

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• Generator electric motor in reverse
• Mechanical energy into Electrical
• Energy easily moved by conductors and easily
  converted to another form
• Moving coil of wire within a magnetic field
  induces a current in the wire
• Produces AC because of the switch in direction
  of magnetic fields in the permanent magnets
• Faradays Law of Induction faster the solenoid
  turns in the magnetic field the higher the
  voltage
• Turbine forced to turn by wind, falling water,
  and expanding steam from burning coal or nuclear
  power

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• Transformers step-up or step-down voltage to
  efficiently by increasing or decreasing the
  number of coils around an iron core
• V1 x N2 V2 x N1

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Magnetic Field Strength

• Electric fields produce electric force per unit
  of charge E k qq/r² E N/C
• Magnetic fields produce magnetic force per unit
  of charge depending on velocity
  B F magnetic / q v B N/C m/s T
• F mag B q v
• Magnetic Field produced by current
  B F magnetic/ I x L B N/C/s m T

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Uses of Magnetism

• Solenoids, speakers, doorbells, galvanometers,
  motors and generators, ignition coils, CAT scans
  and MRI.

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Electromagnetic Waves

• Electromagnetic Wave transverse wave of
  electromagnetic radiation
• Energy is stored in electric and magnetic fields
  and transferred in the form electromagnetic waves
• Oscillating electric and magnetic fields
  propagated perpendicular to one another
• Produced by an exited electron (electric field)
  returning to ground state
• Quantized (Plank) Photon (Einstein)
• Dual Nature Particle and Wave-like