generators and microphones

• alternators create an alternating current
• dynamos create a direct current
• how do alternators work?

  • alternators rotate a coil in a magnetic field
  • as the coil spins a current is induced and the current changes direction every half turn
  • slip rings are used so there is a continuous flow of current
  • this produces a alternating potential difference
• dynamos have spilt ring commutators so the current remains flowing in the same direction
• what does an oscilloscope show?

  how the potential difference generated in the coil changes over time
• in an oscilloscope for the alternating currents line goes up and down crossing the horizontal line
• in an oscilloscope the direct current goes up and down but remains above the horizontal line
• microphones generate current from sound waves
• how do microphones generate current?

  • sound waves hit a flexible diaphragm that is a attached to a coil of wire wrapped around a magnet
  • this causes the coil to move in the magnetic field which generates a current