Electromagnetic Induction

1
Electromagnetic Induction

• Motional Electromagnetic Induction
• Use a magnetic field to create a current
• emf (electromotive force) potential difference
• Where does the energy come from? ? work !

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Electromagnetic Induction

• Induction a coil and a magnet
• The amount of induced emf depends on
• 1. Strength of the magnetic field
• 2. Relative speed of the coil and magnet
• 3. Area of the loops
• 4. Number of loops
• More work is required to move the magnet through
  a coil with many loops.
• Why?

3
Electromagnetic Induction

• Electric guitars
• The string oscillates above a permanent magnet
  and coil

4
Electromagnetic Induction

• Magnetic flux
• The amount of a magnetic field that passes
  through a surface FB BA cos?

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Electromagnetic Induction

• Faradays Law
• The emf is proportional to the number of loops
  times the rate of change of the magnetic field in
  the loops

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Electromagnetic Induction

• Generators
• Mechanical energy input with electrical energy
  output
• Opposite of electric motors

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Electromagnetic Induction

• Transformers
• Used to increase or decrease an alternating
  voltage
• Primary and secondary windings
• Step-up or step-down
• The iron core transfers the magnetic field from
  one coil to the other

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Electromagnetic Induction

• Transformers

9
Electromagnetic Induction

• Transformers
• Power pole