Electromagnetic Induction

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Electromagnetic Induction

• the basis of motors and generators

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Electric Current in a Magnetic Field

• Current in a wire produces a force in a magnetic
  field.
• The force is perpendicular to both the direction
  of the current and the direction of the field.
• Technology produces motors and meters.
• Direction of current must be changed to get
  rotational motion.

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Convert magnetism into electricity

• Oersted showed that a current produces a magnetic
  field
• Changing the placement of a conducting wire in a
  magnetic field produces current

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called Electromagnetic Induction
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Producing voltage

• moving a coil of wire in a magnetic field
  produces voltage and current.
• movements of the diaphragm of a microphone will
  move wires in a magnetic field producing slight
  current that can be amplified.

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Electric Generator

• move coil in a magnetic field
• amount and direction of current changes
• results in alternating current

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AC Current
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Interactions between electricity and magnetism

• Changing magnetic field produces an electric
  current.
• The electric current produces a magnetic field.
• The two fields react.
• Used to make an induction motor for amusement
  park rides and star wars weapons. Also used to
  make an electric guitar.

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Transformers

• increases or decreases AC voltage
• based on induction
• insulated current-carrying wire coiled on one
  side of iron ring (primary)
• second wire coiled on other side of iron ring
  (secondary)

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Faradays Law

• The induced voltage in a coil is proportional to
  the product of the number of loops and the rate
  at which the magnetic field changes within those
  loops.

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Math of Transformers

• secondary voltage turns on secondary
• ------------------------- ---------------------p
  rimary voltage turns on primary
• Vs/Vp Ns/Np
• Vp Ip Vs Is (ideal transformer power is
  conserved)
• Is/Ip Vp/Vs Np/Ns

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Why AC won the battle of the current

• Thomas Edison wanted the US electrical system to
  be DC.
• Tesla thought AC would be better.
• AC won
• AC can make motor and generators easier
• Easy to change voltage
• transmit at high voltage, use at low voltage
• but Edison became richer and better known.