Induced potential and the generator effect: Magnetism and electromagnetism: Physics: GCSE (9:1)

• Induced potential difference

  When an electrical conductor moves relative to a magnetic field or if there is a change in the magnetic field around a conductor, a potential difference is induced across the ends of the conductor

  
• Induced current

  If the conductor that has had a potential difference induced across its ends is part of a complete circuit, a current is induced in the conductor

  
• The generator effect


  When the movement of a conductor relative to a magnetic field causes a potential difference and a current (if part of a complete circuit) to be induced in a conductor

  
• Magnetic field generated by the induced current


  An induced current generates a magnetic field that opposes the original change, either the movement of the conductor or the change in magnetic field
• How to reverse the direction of the induced potential difference/current

  Reverse direction of movement of the magnet or the coil
• Factors affecting the size of the induced potential difference/current

  Speed of movement, magnetic field strength is increased, number of turns on the coil
• Generator


  A device that uses the generator effect to convert kinetic energy into electrical energy

  
• Alternator


  An electrical generator which produces alternating current (an ac generator)

  
• Structure of an alternator

  Consists of a coil of wire rotating in a magnetic field and two slip rings

  
• Sine curve

  The potential difference produced by an ac generator follows the shape of the graph obtained for y = sin x

  
• Dynamo


  An electrical generator which produces direct current (a dc generator)

  
• Structure of a dynamo

  Consists of a coil of wire rotating in a magnetic field and a split ring commutator

  
• Moving-coil microphone


  A microphone in which electrical signals are produced when pressure variations in sound waves vibrate a coil of wire inside a magnetic field