topic 7 magnetism and electromagnetism

• What are the two types of poles in magnets?

  North and South Poles
• What happens when two magnets with the same poles are brought together?

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

  They attract each other.
• What defines a permanent magnet?

  It is always magnetic and always has poles.
• What are induced magnets?

  Materials that are magnetic but do not have fixed poles.
• How can induced magnets be made into temporary magnets?

  By stroking them with a permanent magnet.
• What happens to the domains in a material when it is stroked with a permanent magnet?

  They align in the same direction, creating a temporary magnet.
• Which materials are commonly known to be magnetic?

  Iron, Nickel, and Cobalt.
• How do magnetic field lines behave?

  They point from North to South.
• What happens to the strength of a magnetic field as the distance from the magnet increases?

  The strength decreases with distance from the magnet.
• How can plotting compasses be used in relation to magnetic fields?

  They show the direction of the magnetic field at a certain point.
• What is the significance of Earth's core in relation to magnetism?

  The core is magnetic and creates a large magnetic field around the Earth.
• Why does a freely suspended magnetic compass point North?

  It aligns itself with the Earth's magnetic field lines.
• Where does the magnetic compass actually point in relation to the geographic North Pole?

  It points to a magnetic South Pole located over North Canada.
• What is the relationship between the compass and Earth's magnetic pole?

  The compass is effectively a suspended bar magnet with its north pole aligning with Earth's magnetic pole.
• What is the right hand grip rule used for?

  To determine the direction of the magnetic field produced by a current-carrying wire.
• How does current affect the strength of the magnetic field around a wire?

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

  The magnetic field strength decreases with greater distance from the wire.
• What is a solenoid and how does it enhance the magnetic effect?


  • A solenoid is a coil of wire.
  • It enhances the magnetic effect by aligning the magnetic field lines.
  • It forms a single giant magnetic field rather than multiple perpendicular fields.
• What factors affect the strength of a solenoid's magnetic field?

  Size of current, length, cross-sectional area, and number of turns (coils).
• How does an iron core affect a solenoid's strength?

  It increases strength as magnetic field lines pass through it more easily than air.
• What is the motor effect?

  • Interaction between two magnets creates a magnetic force.
  • A magnet and a wire also exert a force due to their magnetic fields.
  • The wire is pushed away from the field between the poles.
• How does Fleming's Left Hand Rule help in understanding the motor effect?

  It helps to determine the direction of the force felt on the wire.
• What is the formula for calculating the force in the motor effect?

  Force = Magnetic Flux Density x Current x Length (F = BIL).
• What is the unit of Magnetic Flux Density?

  Tesla
• How do electric motors work?

  • Permanent magnets lie in fixed positions.
  • A coil of current-carrying wire lies on an axis between them.
  • Forces on opposite sides of the coil cause it to rotate.
• What is electromagnetic induction?

  • It occurs when there is relative movement between a conductor and a magnetic field.
  • A potential difference is induced across the conductor.
  • A current flows if the conductor forms a complete circuit.
• How do electric generators (dynamos) work?

  • A coil of wire rotates between two permanent magnets.
  • The movement causes the wire to cut through the magnetic field.
  • This creates a potential difference and induces current.
• What type of current does a basic alternator produce?

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

  By connecting the ends to a split ring commutator, reversing the current each half-rotation.
• How do transformers work?

  • AC in the primary coil creates a changing magnetic field.
  • This induces a current in the secondary coil.
  • More coils on the secondary increase voltage (step-up transformer).
  • Fewer coils decrease voltage (step-down transformer).
• What happens if the primary current in a transformer is DC?

  The magnetic field produced will be constant, not inducing anything in the secondary coil.
• How do dynamic microphones work?

  • They produce a current proportional to the sound signal.
  • A fixed magnet is at the center with a coil of wire around it.
  • Pressure variations cause the coil to move, inducing current.
• How do loudspeakers operate?

  • The setup is similar to dynamic microphones but in reverse.
  • Current flows into the coil, causing it to move.
  • The movement produces pressure variations, creating sound.
• magnetic field

  
• cross- away & dot- towards (current)

  
• solenoids diagram - to figure out poles imagine looking down it if theres an N it is anticlockwise and vice versa

  
• fleming’s left hand rule (don’t mix up the fingers if asked to label)

  
• generator effect

  
• alternator- ac produced