Induced Potential, Transformers and the National Grid

• Why must the current flowing through the primary coil of a transformer be alternating?

  To induce current in the secondary coil
• Why is iron used as the core for a transformer?

  It is easily magnetised
• What electromagnetic effect does a microphone utilize?

  The generator effect
• How does a microphone convert sound waves?

  It converts pressure variations into alternating current
• What is the basic makeup of a transformer?

  • A primary coil
  • A secondary coil
  • Wrapped around an iron core
• What can be said about the direction of the magnetic field produced by an induced current?

  It opposes the change that induced the current
• What are two ways the generator effect is used?

  In an alternator and a dynamo
• What happens to an electrical conductor in a changing magnetic field?

  A potential difference is induced across its ends
• What is required for an induced potential difference to cause current flow?

  The conductor must form a closed loop
• What happens when an electrical conductor moves relative to a magnetic field?

  A potential difference is induced across its ends
• What can be said about the electrical power input and output of a 100% efficient transformer?

  Input power equals output power