P2.Magnetism And Electromagnetism

• What are the poles of a magnet?

  The places where magnetic forces are strongest
• What happens when two like poles of magnets are brought together?

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

  They attract each other
• What type of force is attraction and repulsion between magnetic poles?

  Non-contact force
• What does a permanent magnet do?

  Produces its own magnetic field
• What is an induced magnet?

  A material that becomes a magnet in a field
• What happens to an induced magnet when removed from a magnetic field?

  It loses most/all of its magnetism quickly
• What are the key characteristics of permanent and induced magnets?

  • Permanent magnets produce their own magnetic field.
  • Induced magnets become magnets in a magnetic field.
  • Induced magnets lose magnetism when removed from the field.
• What is the magnetic field?

  The region around a magnet where force acts
• What type of materials are affected by a magnetic field?

  Iron, steel, cobalt, and nickel
• How does the strength of a magnetic field change with distance from the magnet?

  It decreases with distance
• Where is the magnetic field strongest on a magnet?

  At the poles of the magnet
• How is the direction of a magnetic field determined?

  By the force on another north pole
• What does a magnetic compass contain?

  A small bar magnet
• What does the compass needle point to?

  The direction of the Earth's magnetic field
• How can the magnetic field pattern of a magnet be plotted using a compass?

  1. Place the compass near the magnet.
  2. Mark the direction of the compass needle.
  3. Move the compass around the magnet.
  4. Connect the points to visualize the field lines.
• What is the shape of the magnetic field around a solenoid?

  • Similar to that of a bar magnet
  • Strong and uniform inside the solenoid
• What increases the strength of the magnetic field in a solenoid?

  Adding an iron core
• What happens when a current flows through a conducting wire?

  A magnetic field is produced around the wire
• What is the formula for the force on a conductor in a magnetic field?

  $F =$$BIl$
• What does the variable F represent in the formula $F =$$BIl$?


  Force in newtons, N
• What does the variable B represent in the formula $F =$$BIl$?


  Magnetic flux density in tesla, T
• What does the variable I represent in the formula $F =$$BIl$?


  Current in amperes, A
• What does the variable l represent in the formula $F =$$BIl$?


  Length in metres, m
• What is the motor effect?

  The interaction between a magnetic field and a current
• How does a coil of wire behave in a magnetic field?

  It tends to rotate
• What do loudspeakers and headphones use to convert current variations?

  The motor effect
• What is induced potential?

  Potential difference induced by movement in a magnetic field
• What is the generator effect?

  Induced current generates a magnetic field opposing change
• What is the purpose of an alternator?

  To generate alternating current (AC)
• What is the purpose of a dynamo?

  To generate direct current (DC)
• How do microphones work?

  They convert sound pressure variations into current variations
• What does a basic transformer consist of?

  A primary coil and a secondary coil
• Why is iron used in transformers?

  It is easily magnetised
• What does the ratio of potential differences in a transformer depend on?

  The ratio of the number of turns on each coil
• What happens in a step-up transformer?

  Vs > Vp
• What happens in a step-down transformer?

  Vs < Vp
• What is the relationship between power input and output in transformers?

  Power output equals power input if 100% efficient
• What is the equation for power in transformers?

  $Vs \times Is =$$Vp \times Ip$
• What is the effect of alternating current in one coil on another in transformers?

  It induces a current in the second coil