Alternators and Dynamos

• Generators


  Make use of the generator effect to induce a current
• Alternating current (AC)


  Current that changes direction every half turn
• Direct current (DC)


  Current that flows in the same direction
• Alternators


  1. Rotate a coil in a magnetic field

  2. Construction is like a motor

  3. As the coil (or magnet) spins, a current is induced

  4. Current changes direction every half turn

  5. Have slip rings and brushes to prevent swapping contacts
• Dynamos


  1. Work the same as alternators

  2. Have a split-ring commutator instead of slip rings

  3. Swaps the connection every half turn to keep the current flowing in the same direction
• Oscilloscope


  • Shows how the potential difference generated in the coil changes over time
  • For AC, the line goes up and down, crossing the horizontal axis
  • For DC, the line stays above the axis (the pd is always positive)
  • The height of the line is the generated potential difference at that time
  • Increasing the frequency of revolutions increases the overall pd, but it also creates more peaks
• Increasing revolutions


  Increases the overall potential difference, but also creates more peaks