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Electromagnetic Induction

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Electromagnetic Induction Electromagnetic Induction Motion of a magnet in a coil or loop creates (induces) voltage If coil is connected to complete circuit, current ... – PowerPoint PPT presentation

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Title: Electromagnetic Induction


1
Electromagnetic Induction
2
Electromagnetic Induction
  • Motion of a magnet in a coil or loop creates
    (induces) voltage
  • If coil is connected to complete circuit, current
    flows
  • Relative motion is neededit doesnt matter which
    moves, the magnet or the coil
  • Amount of voltage depends on rate of motion and
    number of loops in coil

3
Faradays Law
  • The induced voltage is proportional to the number
    of loops times the rate of change of the magnetic
    field
  • Magnetic field is changed by motion or by
    changing the strength of the field in an
    electromagnet

4
Generators
  • Rotating a coil in a magnetic field will create
    alternating current
  • As coil rotates, amount of magnetic field
    enclosed by loop changes, inducing a changing
    voltage
  • Frequency of alternating current is the same as
    frequency of rotation of the coil
  • Energy is converted from some mechanical form to
    electrical

5
Motors and Generators
  • Both have same parts
  • Motors convert electrical energy to mechanical
    movement using the magnetic force on a moving
    charge to move the coil
  • Generators convert mechanical to electrical by
    using the magnetic force due to the coil movement
    to move the charges through the wire

6
Transformers
  • Two coils of wire wound on the same iron core so
    that changes in the magnetic field of the first
    coil (primary) induce voltage across the second
    coil (secondary)
  • If ac flows through primary, ac is induced in
    secondary
  • Voltage in secondary depends on ratio of turns in
    primary and secondary

7
Transformers
  • If secondary has more turns, than transformer is
    called step-up and voltage is increases
  • If secondary has fewer turns, then is called
    step-down and voltage is decreased
  • Power is not increased so if voltage is stepped
    up, current is reduced

8
Transformer Equations
  • Primary turns Primary voltage
  • Secondary turns Secondary voltage
  • (Voltage x current)p (voltage x current)s

9
Power Transmission
  • Almost all electrical energy is sold as ac
    because it is easy to change voltage using
    transformers
  • High voltage and fairly low currents are used to
    transmit power over long distances
  • This reduces losses due to heating in the wires
  • Voltage is stepped down to 120 V for homes

10
Electric and Magnetic Fields
  • Faradays law holds even if no conductor is
    present
  • A changing magnetic field induces an electrical
    field
  • Maxwell extended Faradays idea to say a changing
    electrical field induces a magnetic field

11
Electrical and Magnetic Fields
  • Electrical and magnetic fields are perpendicular
    to each other
  • Magnitude of induced field is proportional to
    rate of change of the other field
  • Explained operation of electromagnetic waves
  • Speed of light is only speed where induction will
    continue without energy gain or loss
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