P15

• How could magnets be made historically?

  By rubbing iron on lodestone or another magnet
• Why couldn't stronger magnets be made until Victorian times?

  Technology to produce electricity was needed
• When was the explanation for magnetism understood?

  In the 20th Century with atomic ideas
• What materials are magnets made from?

  Iron or steel
• What materials will magnets stick to?

  Iron or steel, cobalt, and nickel
• Where are magnets magnetic?

  At their poles (ends)
• What metals do magnets attract?

  Iron, steel, nickel, and cobalt
• How do magnets interact with each other?

  Like poles repel, opposite poles attract
• What surrounds a magnet?

  A magnetic force field
• What does the magnetic field around a bar magnet look like?

  Strongest at poles, weaker further away
• How can the magnetic field be plotted?

  Using a compass or iron filings
• Which direction do magnetic field lines point?

  From North to South
• What are the ends of a magnet called?

  • The Poles
• What do we call the area around a magnet where a magnetic force exists?

  • The Magnetic Field
• What does the word "attract" mean?

  • Pull together
• What does the word "repel" mean?

  • Push apart
• How was a magnet made up until Victorian times?

  By rubbing steel against a magnet or lodestone
• What happens to the atoms in steel when it becomes a magnet?

  They align North to South
• How does steel's magnetism compare to iron's?

  Steel keeps magnetism; iron loses it slowly
• What are domains in magnetic materials?

  • Groups of atoms aligned in the same direction
  • Usually arranged randomly
• What happens to domains when a magnet is bashed or dropped?

  They can become random, losing magnetism
• What type of magnetic material is iron?

  Soft magnetic material
• What type of magnetic material is steel?

  Hard magnetic material
• How does electric current affect magnetism?

  More current strengthens the magnetic field
• What shape is the magnetic field around a wire?

  Circular in shape around the wire
• What rule predicts the direction of the magnetic field?

  The Corkscrew rule
• What happens when the electric current is reversed?

  The direction of the magnetic field reverses
• How can the magnetic field around a wire be strengthened?

  By coiling the wire into a solenoid
• What does a solenoid's magnetic field resemble?

  Like a bar magnet
• What is an electromagnet?

  A coil of wire with electric current flowing
• What happens to one end of a coil when current flows through it?

  It becomes a north-seeking pole
• What is the other end of the coil called?

  South-seeking pole
• How can the magnetic field in a solenoid be made stronger?

  • Increase the current flowing
  • Increase the number of coils
  • Insert an iron core
• What are the advantages of an electromagnet over a bar magnet?

  • Control strength of magnetic field
  • Change direction of magnetic field
  • Turn it on and off
• How do you make an electromagnet?

  • Wrap wire around an iron nail
  • Connect wire to batteries
  • Test with paperclips
• What was the significance of electromagnets in the Victorian era?

  They produced force for movement
• What can the movement produced by electromagnets be used for?

  Many practical applications
• What is the structure of an electromagnet in a scrap yard crane?

  A series of coils surrounded by iron casing
• How does the operator control the electromagnet in a crane?

  By switching the electric current on/off
• What does a relay do?

  Allows one circuit to control another circuit