Magnetism

• Magnetism


  A set of physical phenomena associated with a magnetic field, which can be produced both by electric current and by magnetic materials
• Magnetic field


  The area of magnetic force around a magnet

  
• Magnetism is the force of attraction or repulsion that acts at a distance. This is due to the magnetic field, which is caused by the movement of electrically charged particles.
• Pierre de Maricourt found that the direction of a needle near a spherical natural magnet formed lines that encircled the sphere

  1269

  
• The lines also passed through two points diametrically opposed to each other. He called the points poles.
• William Gilbert expanded experiments with magnetism to a variety of materials and suggested the Earth itself was a large permanent magnet


  1600
• Hans Christian Oersted discovered the relationship between electricity and magnetism - an electric current in a wire deflected a nearby compass needle


  1819
• Faraday further connected electricity and magnetism - a changing magnetic field creates an electric field. Maxwell - a changing electric field produces a magnetic field.


  1820
• Magnet


  An object that exhibits a strong magnetic field and has the ability to attract materials to itself, e.g. iron

  
• Magnetic poles


  The north (N) and south (S) poles of a magnet
• Two magnets will be attracted by opposite poles and each will repulse the same pole of the other magnet
• Magnetism has many applications in modern life
• Properties of magnets


  • Magnets attract iron and materials that contain iron
  • Magnets attract or repel other magnets
  • One part of a magnet always points north

  
• Magnetic field lines


  The lines that map out the magnetic field around a magnet

  
• Magnetic field lines spread out from one pole, curve around the magnet, and return to the other pole
• Magnetic domain


  A grouping of billions of atoms that have their magnetic fields lined up in the same direction
• In a magnetized material, all or most of the magnetic domains are arranged in the same direction
• Ferromagnetic material


  A material that has strong magnetic properties
• Temporary magnet


  A magnet made from a material that easily loses its magnetism
• Permanent magnet


  A magnet made from a material that keeps its magnetism for a long time

  
• Electric current


  The continuous flow of electric charges through a material
• To produce electric current, charges must flow continuously from one place to another
• Electric circuit


  A complete, unbroken path through which electric charges can flow
• Conductor


  A material through which charge can easily flow
• Insulator


  A material through which charges cannot flow easily
• Voltage


  The difference in electrical potential energy between two places in a circuit
• Voltage causes a current in an electric circuit
• Voltage source


  A device that creates a potential difference in an electric circuit
• Resistance


  The greater the resistance, the less current there is for a given voltage
• Electromagnetism


  The relationship between electricity and magnetism
• Electromagnet


  A solenoid with a ferromagnetic core
• An electromagnet is a strong magnet that can be turned on and off
• Electromagnetic induction


  Generating an electric current from the motion of a conductor through a magnetic field
• Direct current


  A current consisting of charges that flow in one direction
• Alternating current


  A current that consists of charges that move back and forth in a circuit
• Electric generator


  A device that converts mechanical energy into electrical energy
• A generator uses motion in a magnetic field to produce an electric current
• Transformer


  A device that increases or decreases voltage, consisting of two separate coils of insulated wire wrapped around an iron core
• Step-up transformer


  A transformer that increases voltage
• Step-down transformer


  A transformer that decreases voltage