alternators and dynamos

• • in an alternator , a rotating magnet is used with a fixed coil of wire
  • as the magnet rotates , the coil passes the magnetic field causing it to alternate
  • this induces an alternating potential and an alternating current
• • in a dynamo , the coil rotates and the magnet is fixed
  • as the coil rotates it generates a potential difference in one direction
  • the use of a split ring commutator means that once the coil has passed the upright position , the connections are reversed
  • as a result, the direction of the current output is always in the same direction
• • the graphs of potential difference against time can be used to determine the speed of rotation - two 0 points is the time for half the rotation
• for alternators the speed of rotation is the frequency of the alternating current
• ways to increase the size of the current

  • increasing the strength of the magnetic field
  • increasing the number of turns
  • increasing the area of the coil
  • increasing the rotation speed
  • increasing the rotation speed increases the size and frequency of the current
• 1. potential difference is at its maximum because the coil is sweeping directly through the field lines at its fastest rate
  2. potential difference is 0 because the coil is vertical and parallel to magnetic fields so dont cut through field lines
  3. potential difference have reversed its direction

  
• • two peaks for one full rotation
  • each side passes through twice