Magnetic Field

• All magnets are surrounded by a magnetic field that they produce
• The earth has a magnetic field because of the iron core
• The south pole is located in the Northern hemisphere which is how compasses determine north and south as the north pole of the compass is attracted to the south pole in the northern hemisphere
• Magnetic field - the region around a magnet where a force acts on another magnet or on a magnetic material e.g. iron, steel, cobalt and nickel
• Magnetic fields are 3D, surrounding the magnet in 360 degrees
• Magnetic field lines - used to represent the strength and direction of a magnetic field

  • direction is shown by arrows and corresponds to the direction of the force a north pole would feel if it was placed in that magnetic field at that moment
  • strength is shown by spacing
• Rules of spacing with magnetic field lines:

  • closer and denser together, strong magnetic field
  • further apart, weak magnetic field
• Rules of drawing magnetic field lines:

  • always go from north to south which is indicated by an arrow in the middle of the line
  • never touch or cross other field lines
• Tips on drawing magnetic field lines:

  • ALWAYS ADD ARROWS pointing away from the north pole
  • make sure magnetic field lines are further apart as he distance from the magnet increases
• Magnetic fields are strongest at the poles of a bar magnet and the magnetic field becomes weaker as you go further away from the magnet

  • poles - where the magnetic field lines are closest together
  • further away form the magnet - where the magnetic field lines are further apart

  
• A uniform magnetic field is produced in the gaps between opposite poles

  • this can be achieved by using two bar magnets and pointing the opposite poles (north and south) of two magnets a few centimetres apart
  • points outside the gap is not a uniform magnetic field
• Uniform magnetic fields have the same strength and direction at all points

  • to show that they have the same strength on a diagram, the spacing between each line must all be equal to indicate that field strength is equal at every point between the poles
  • to show that they are all acting in the same direction, there needs to be an arrow showing the direction from north pole to south pole
• A uniform magnetic field can be determined by using plotting compasses that point from north to south or iron fillings
• Magnetic forces - a push or pull experienced by two magnetic forces

  • happens because of the interactions between the fields e.g. 2 bar magnets attracting and repelling
• Attracting and repelling bar magnets

  • attracting magnetic fields align with eachother, creating an attractive force
  • repelling magnetic fields don’t align with eachother, creating an invisible barrier, repelling eachother
• Attracting and repelling bar magnets

  A) pushes the poles

  B) opposite poles attract

  C) uniform field

  D) repel

  E) no field

  
• • Magnetic field lines around various configurations of bar magnets

  
• Define magnetic field

  A region where a magnet experiences a force
• How is an electric field and a magnetic field related?

  magnetic fields are electric fields when an electrically charged object starts moving
• What type of current can create magnetism?

  Electron current
• Why do protons not create magnetism even though they are magnetic?

  They are weak tiny magnets
• What is the rule on whether an element is magnetic or not?

  Elements in group 1,2, 3 and 8 aren't magnetic as they have full or close to full shell
• How can you make the domains aligned in a material?

  You can make the domains aligned by using a strong magnetic field near the material
• Don't forget to draw the field lines around the poles
• What is a uniform magnetic field?

  A magnetic field that has the same strength and direction at all points
• What direction do you draw the magnetic field lines?

  From north to south