Electromagnetic Induction

• What happens when an electrical conductor moved to a magnetic field?

  A voltage (potential difference) is induced across the conductor
• What happens to an electrical conductors when there is a change to the magnetic field that it is placed in?

  The voltage is also changed
• How do you produce an electric current using a magnet and a conductor on a small-scale?

  Move a coil of wire between magnetic poles/move a magnet within a coil of wire, once a voltage is induced, if the circuit is complete, a current will also be induced
• How is electrical current produced on a large-scale?

  An electromagnet is rotated around a coil
• What factors affect the size of an induced voltage?

  The number of turns on the coil of wire, how strong the magnetic field is, the speed of the movement
• What is required for an induced potential difference to cause a current flow?

  Closed circuit
• What can be said about the direction of the magnetic field produced by an induced current?

  The direction of the field is such that it opposes the change that induced the current, this change is either the movement of the conductor or a change to the field
• What are two ways that the generator effect is used to generate different types of current?

  In an alternator to produce AC, in a dynamo to produce DC
• How does a dynamo generate current?

  A coil of wire rotates inside a magnetic filed, a commutator is used to ensure it continues rotating in the same direction, therefore keeping the current flowing in the same direction (DC)
• How is electromagnetic induction used in alternators to generate alternating current?

  A coil of wire rotates in a magnetic field, the end is connected to slop rings which will cause the current to change direction while rotating so that an AC is produced
• Electromagnetism in microphones


  The generator effect, converts the pressure variations in sound waves into an alternating current
• Electromagnetism in loudspeakers


  The motor effect is used to convert varation in the current of an electrical circuit into the pressure variations which produce audible sound
• How do loudspeakers work?

  A cone wrapped in wire is connected to an AC power supply and placed in a permanent magnetic field. When current flows through the wire, it creates a magnetic field which interacts with the permanent field. This produces a force causes the cone to vibrate, producing sound
• How is the pitch of the sound from a loudspeaker changed?

  The frequency of the AC current is altered, creating a different frequency of vibration in the cone
• How do microwaves convert sound into electrical signals?

  Sound produces pressure variations which cause the diaphragm to vibrate, so a coil of wire attached to it also does. Movement in a magnetic field means that a voltage is induced, as there is a complete circuit a current is also created