Magnetism and Electromagnetism

• Magnets produce magnetic fields
• Name a magnetic metal

  • iron
  • Steel
  • Nickel
  • Cobalt
• Magnetic lines always go from north to south
• The force between a magnet and a magnetic material is always attractive no matter the pole of a magnet
• Compasses show the directions of magnetic fields
• Magnets can be permanent or induced
• permanent magnets produce their own magnetic field
• induced magnets are magnetic materials that turn into a a magnet when they’re put into a magnetic field
• the force between permanent and induced magnet is always attractive
• A moving charge creates a magnetic field
• When a current flows through a wire a magnetic field is created around the wire and the field is made up of concentric circles perpendicular to the wire
• What is the right hand thumb rule?

  • using right hand point thumb in direction of current and curl fingers
  • the direction of your fingers is the direction of the field
• A solenoid is a coil of wire
• You can increase the strength of the magnetic field that a wire produces by wrapping the wire into a coil called a solenoid
• The magnetic field is just like a bar magnet in a solenoid
• • You can increase the field strength of the solenoid even more by putting a block of iron in the centre of the coil
  • this soft iron core becomes an induced magnet whenever current is flowing
• A solenoid with an iron core is called an electromagnet
• Electromagnets are used in some cranes to attract and pick up things made from magnetic materials like iron and steel in scrap yards using an electromagnet means it can be switched on and off
• Electromagnets can be used within circuits to act as switches
• The motor effect can happen when you put a current-carrying wire in a magnetic field
• A current in a magnetic field experiences a force
• What is the motor effect?

  a current carrying wire is put in between magnetic poles the magnetic field around the wire interacts with the magnetic field it’s been placed in and causes the magnet and conductor to exert a force on each other and can cause the wire to move
• In the motor effect the force always acts at right angles to the magnetic field of the magnets and the direction of the current of the wire
• The force acting on a conductor in a magnetic field depends on:

  • magnetic flux density
  • size of the current through the conductor
  • length of conductor that’s in the magnetic field
• F=BIL


  This calculates the magnetic flux density (T, tesla)
• what does I stand for in F=BIL?

  current (A)
• What does the B stand for in F=BIL?

  Magnetic flux density (T, tesla)
• You can find the direction of the force with Fleming’s Left-Hand rule
• In the Fleming’s Left Hand rule what does the first finger represent?

  Field
• In the Fleming’s Left Hand rule what does the second finger represent?

  Current
• In the Fleming’s Left Hand rule what does the thumb represent?

  Force/Motion
• A current carrying coil of wire rotates in a magnetic field