the alternator and dynamo

• Alternator


  A coil of wire rotating in a magnetic field, connected to two metal rings called commutators that allow the current to pass out of the coil
• How an alternator generates an alternating current

  1. Potential difference is induced when the wire passes through the magnetic field

  2. The red side of the wire always connects to ring A, the orange side always connects to ring B

  3. When the coil is horizontal, the potential difference is maximum as the wire is sweeping through the field lines at the fastest rate

  4. When the coil is vertical, the potential difference falls to zero as the coil is moving parallel to the field

  5. As the coil continues rotating, the potential difference reverses direction as the sides of the coil are now moving in the opposite direction
• Factors that increase the size of the alternating current in an alternator

  • Stronger magnetic field
  • More turns on the coil
  • Larger coil area
  • Higher rotation speed
• Dynamo


  Produces a direct current (DC)
• How a dynamo generates a direct current

  1. Has a split ring commutator with two sides A and B

  2. The side of the coil moving down is connected to part A, the side moving up is connected to part B

  3. This means the direction of the potential difference and current do not reverse as the coil rotates

  4. Get two peaks in the potential difference graph for each full rotation of the coil, as each side passes through the field twice
• Alternating current (AC) is produced by an alternator, direct current (DC) is produced by a dynamo