Magnetic Effects of Electric Current

• A pictorial representation that gives the direction of the magnetic field at various points in a magnetic field is called a map of the magnetic field
  
  
• Let us now map the magnetic field by using a compass
  
  
• Fix a sheet of paper on a drawing board
  
  
• Place a bar magnet on the sheet of paper
  
  
• Trace the boundary NS of the bar magnet
  
  
• Place a compass at the North Pole
  
  
• The magnetic needle comes to rest in a particular direction
  
  
• Mark the ends of the needle. The tail end of the needle is the south pole and the tip of the needle is the north pole
  
  
• Now move the magnetic needle in such a way that its tail (south pole) always points towards the north pole of the bar magnet
  
  
• Mark the new position of its north pole
  
  
• Repeat this until you reach the other end of the magnet
  
  
  
  
• Join the points
  
  
• These points form a curve
  
  
• The curved line represents a magnetic field line or magnetic line of force
  
  
• Repeat the above procedure and draw as many lines as you can

Properties of Magnetic Lines of Force

• Lines of force are closed and continuous curves
  
  
• Outside the magnet the lines of force are directed from the south pole towards the south pole of the magnet
  
  
• But within the magnet the magnetic lines are directed from the south pole towards the north pole
  
  
• Lines of force repel each other
  
  
• Lines of force never intersect