Magnetism and Electromagnetism

• What are the two types of poles in a magnet?

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

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

  They attract each other.
• What is a characteristic of permanent magnets?

  They are always magnetic and always have poles.
• What are induced magnets?

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

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

  They align in the same direction, creating a temporary magnet.
• Which materials can be induced into temporary magnets?

  Iron, Nickel, and Cobalt.
• In a magnetic field, where do the field lines point?

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

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

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

  Plotting compasses.
• What is the nature of Earth's core in relation to magnetism?

  The core is magnetic and creates a large magnetic field around the Earth.
• How does a freely suspended magnetic compass behave in relation to Earth's magnetic field?

  It aligns itself with the Earth's field lines and points North.

  
• Why does a compass not point to the Geographic North Pole?

  Because it points to a magnetic South Pole located over North Canada.
• What is the relationship between Earth's magnetic pole above Canada and the geographic poles?

  Earth's magnetic pole above Canada is a magnetic South Pole.
• 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 to the strength of the magnetic field with greater current?

  The magnetic field becomes stronger.
• How does distance from the wire affect the magnetic field strength?

  It weakens the field.
• What is a solenoid and its characteristics?

  • A solenoid has a magnetic field shape similar to a bar magnet.
  • Coiling the wire enhances the magnetic effect.
  • An iron core increases strength as it allows magnetic field lines to pass through more easily.
  • Factors affecting strength: size of current, length, cross-sectional area, number of turns (coils), and using a soft iron core.
• What is the motor effect?

  It is the interaction between two magnets that results in a magnetic force of attraction or repulsion.
• How do the magnetic fields of a magnet and a wire interact?

  The two magnetic fields interact, causing a force on the wire.
• What is the shape of the magnetic field around a wire?

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

  The force is at right angles to both the direction of the current and the magnetic field lines.
• What does Fleming’s Left Hand Rule help determine?

  It helps to work out the unknown factor among the force, magnetic field, and current direction.
• What is the formula for force in the context of magnetic fields?

  Force = Magnetic Flux Density × Current × Length.
• In what unit is Magnetic Flux Density measured?

  Tesla.
• How do electric motors work?

  • Permanent magnets are 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.
  • This can be verified using Fleming’s Left Hand Rule.

  
• What is electromagnetic induction?

  It is the induction of a potential difference across a conductor due to relative movement with a magnetic field.
• What happens when the magnetic field changes during electromagnetic induction?

  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, inducing a potential difference.
• What is the role of a turbine in electric generators?

  The turbine spins, turning the coil of wire to cut through the magnetic field.
• 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.

  
• What is the function of transformers?

  • AC in the first coil creates a changing magnetic field.
  • This changing magnetic field induces a current in the secondary coil.
  • More coils on the secondary create a step-up transformer (increased voltage).
  • Fewer coils create a step-down transformer (decreased voltage).
• 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.
• What is the relationship between the number of coils and voltage in transformers?

  More coils on the secondary increase voltage, fewer coils decrease voltage.
• 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 in sound waves cause the coil to move, inducing current.
  • This current is sent to a loudspeaker.

  
• How do loudspeakers operate?

  • The setup is identical to dynamic microphones but works in reverse.
  • Current flows into the coil, interacting with the magnetic field.
  • This interaction causes the coil to move, producing sound.