electromagnetic induction

• Potential difference


  The energy given to the charge carriers in a circuit, measured in volts (V)
• Voltage


  The potential difference across a cell, electrical supply or electrical component, measured in volts (V)
• Electromagnetic induction


  The production of a potential difference (voltage) when a conductor, such as a wire, is moved through a magnetic field or exposed to a varying magnetic field
• Generator effect


  When motion between a conductor and a magnetic field creates electricity, i.e. a magnet is moved into a coil of wire
• A coil of wire is moved in a magnetic field


  A potential difference is induced
• A magnet is moved into a coil of wire


  A potential difference is induced
• The induced voltage produces an induced current if the conductor is connected in a complete circuit
• The induced current creates a magnetic field around itself, which opposes the original change
• Factors affecting the induced potential

  • Direction of movement of the magnet relative to the coil
  • Reversing the direction of movement (magnet moved out or other pole moved in)
• Increasing the speed of movement


  Increases the induced potential difference or current
• Increasing the magnetic field strength

  Increases the induced potential difference or current
• Increasing the number of turns on the coil


  Increases the induced potential difference or current
• Electromagnetic induction


  Can create a voltage by movement of a conductor in a magnetic field
• Voltage created by electromagnetic induction

  Can make current flow, and the effect is used in electricity generation and microphones
• DC generator


  Device that converts kinetic energy into electrical energy
• Electromagnetic induction


  Can create a voltage by movement of a conductor in a magnetic field
• Potential difference


  The potential difference (or voltage) of a supply is a measure of the energy given to the charge carriers in a circuit. Units = volts (V). This is the voltage between two points that makes an electric current flow between them.
• Voltage created by electromagnetic induction

  Can make current flow, and the effect is used in electricity generation and microphones
• Dynamo


  An electrical generator which produces direct current, a DC generator
• AC generator


  Device that converts kinetic energy into electrical energy
• How a dynamo works

  1. Magnet rotates inside a fixed coil of wire

  2. Split ring commutator changes the coil connections every half turn

  3. Induced potential difference is about to change direction, the connections are reversed

  4. Current to the external circuit always flows in the same direction
• Potential difference


  The potential difference (or voltage) of a supply is a measure of the energy given to the charge carriers in a circuit. Units = volts (V). This is the voltage between two points that makes an electric current flow between them.
• The output of a rotating dynamo can be shown on a potential difference-time graph as a sine curve that stays in the same direction all the time
• Factors that can increase the maximum potential difference or current of a dynamo

  • Increasing the rate of rotation
  • Increasing the strength of the magnetic field
  • Increasing the number of turns on the coil
• AC


  Alternating current, eg the mains supply of electricity from a plug is alternating current.
• Alternator


  An electrical generator which produces alternating current, an ac generator.
• How an AC generator works

  1. Coil of wire rotating in a magnetic field

  2. One side of coil moves up through magnetic field, inducing potential difference in one direction

  3. As rotation continues, that side of coil moves down, reversing induced potential difference

  4. This produces alternating current (AC)
• The output of an alternator as it rotates can be represented on a potential difference-time graph with a sine curve
• Factors that can increase the maximum potential difference or current of an AC generator

  • Increasing the rate of rotation
  • Increasing the strength of the magnetic field
  • Increasing the number of turns on the coil
• Electromagnetic induction


  Creating a voltage by movement of a conductor in a magnetic field
• The induced potential difference travels in the opposite direction when the coil is at 270 degrees compared to when it is at 90 degrees
• Electromagnetic induction


  • Can create a voltage
  • Can make current flow
  • Used in electricity generation and microphones
• Microphone


  A device that converts sound waves into electrical signals
• How a microphone works

  1. Pressure variations in sound waves cause diaphragm to vibrate

  2. Vibrations of diaphragm cause vibrations in coil

  3. Coil moves relative to permanent magnet

  4. Potential difference induced in coil

  5. Induced potential difference causes current to flow in circuit

  6. Changing size and direction of induced current matches vibrations of coil

  7. Electrical signals generated match pressure variations in sound waves
• Moving-coil microphone


  Electrical signals produced when pressure variations in sound waves vibrate a coil of wire within a magnetic field
• The generator effect is used in microphones to induce a changing current from the pressure variations of sound waves