topic 7

• What are the two types of poles in magnets?

  North and South Poles
• What happens when same poles of magnets are brought together?

  They repel each other
• What occurs when opposite poles of magnets are brought together?

  They attract each other
• What are permanent magnets?

  Always magnetic, always have poles
• What are induced magnets?

  Materials that are magnetic but not fixed poles
• How can induced magnets become temporary magnets?

  By stroking them with a permanent magnet
• What happens when you stroke an induced magnet with a permanent magnet?

  It aligns the domains in the same direction
• Which materials can become induced magnets?

  Iron, Nickel, Cobalt
• In which direction do magnetic field lines point?

  From North to South
• How does the strength of a magnetic field change with distance?

  It decreases with distance from the magnet
• What direction do magnetic field lines point at any point?

  Towards the south pole and away from north
• What tool can be used to visualize magnetic field direction?

  Plotting compasses
• What is the Earth's core's role in magnetism?

  It creates a large magnetic field around Earth
• How does a magnetic compass behave in relation to Earth's magnetic field?

  It aligns with Earth's field lines and points North
• Where does a compass point in relation to the geographic North Pole?

  It points to a location over North Canada
• Why is Earth's magnetic pole above Canada considered a magnetic South Pole?

  Because like poles repel each other
• What does current produce around a wire?

  A magnetic field
• How is the direction of the magnetic field around a wire determined?

  By the right hand grip rule
• What happens when plotting compasses are placed around a wire?

  They show the direction of the magnetic field
• How does the strength of a magnetic field change with current?

  Greater current produces a stronger magnetic field
• How does distance from a wire affect the magnetic field strength?

  Greater distance results in a weaker field
• What is a solenoid and its properties?

  • Magnetic field shape similar to a bar magnet
  • Coiling wire enhances magnetic effect
  • Iron core increases strength
  • Factors affecting strength:
  • Size of current
  • Length of solenoid
  • Cross-sectional area
  • Number of turns (coils)
  • Using a soft iron core
• What is the motor effect?

  Interaction of magnets creates a force
• How do the magnetic fields of a magnet and a wire interact?

  They exert a force on each other
• What is the orientation of the magnetic field around a wire?

  It is circular
• How does the force on a wire relate to the direction of current and magnetic field?

  It is at right angles to both
• How does Fleming's Left Hand Rule work?

  • Each direction is 90° to each other
  • Used to determine the unknown factor (usually force direction)
  • Current is conventional current, opposite to electron flow
• What is magnetic flux density measured in?

  Tesla
• How do electric motors operate?

  Coil of wire rotates between fixed magnets
• What happens to the forces on the sides of the coil in an electric motor?

  One side moves up, the other down
• What induces a potential difference in a conductor?

  Relative movement between conductor and magnetic field
• What happens if the magnetic field changes while a conductor is moving?

  A current flows if there's a complete circuit
• How do electric generators (dynamos) work?

  Coil rotates between two permanent magnets
• What does the movement of the wire in a generator cause?

  It cuts through the magnetic field
• What type of current does a complete circuit produce in a generator?

  Alternating current (AC)
• How is direct current (DC) produced in a dynamo?

  Using a split ring commutator
• What is the function of a transformer?

  To change voltage levels in AC circuits
• What happens when AC flows in the first coil of a transformer?

  It creates a changing magnetic field
• What does a step-up transformer do?

  Increases voltage with more coils on secondary
• What does a step-down transformer do?

  Decreases voltage with fewer coils on secondary