• All magnets are surrounded by a?magnetic field
• A magnetic field is defined as:

The region around a magnet where a force acts on another magnet or on a magnetic material (such as iron, steel, cobalt and nickel)

Magnetic Field Lines

• Magnetic field lines are used to represent the?strength?and?direction?of a magnetic field
• The direction of the magnetic field is shown using?arrows
• The?strength?of the magnetic field is shown by the?spacing?of the magnetic field lines
  • If the magnetic field lines are?close together?then the magnetic field will be?strong
  • If the magnetic field lines are?far apart?then the magnetic field will be?weak

   

• There are some rules which must be followed when drawing magnetic field lines. Magnetic field lines:
  • Always go?from north to south?(indicated by an arrow midway along the line)
  • Must?never touch or cross?other field lines

   

Magnetic Field Around a Bar Magnet

• The magnetic field is?strongest at the poles
  • This is where the magnetic field lines are?closest?together

   

• The magnetic field becomes?weaker as the distance from the magnet increases
• This is because the magnetic field lines are getting?further apart

The magnetic field around a bar magnet

• Two bar magnets can repel or attract, the field lines will look slightly different for each:

Magnetic field lines for attracting and repelling bar magnets

• Therefore, the magnetic field lines around different configurations of two bar magnets would look like:

Magnetic field lines between two bar magnets

• Two bar magnets can be used to produce a uniform magnetic field
• Point opposite poles (north and south) of the two magnets a few centimetres apart
• A?uniform?magnetic field will be produced in the?gaps?between?opposite poles
  • Note: Outside that gap, the field will?not?be uniform

   

A uniform field is created when two opposite poles are held close together. Magnetic fields are always directed from North to South

• A uniform magnetic field is one that has the?same strength and direction at all points
  • To show that the magnetic field has the same strength at all points there must be?equal spacing?between all magnetic field lines
  • To show that the magnetic field is acting in the same direction at all points there must be an arrow on each magnetic field line going from the?north?pole to the?south?pole

   

• The magnetic field lines are the?same distance apart?between the gaps of the poles to indicate that the field strength is the same at every point between the poles
• This field can be determined by using plotting compasses that will point from?north?to?south?or by using iron filings