Forces on a conductor in a field

• The motor effect


  When a conductor carrying a current is placed in a magnetic field of a magnet causing the conductor and magnet to exert force on each other

  
• Fleming's left hand rule (LHR)

  Used to find the direction of the force on a conductor in a magnetic field by holding your thumb, forefinger and second finger at right angles to each other

  
• What your first finger represents (LHR)

  The direction of the magnetic field from north to south

  
• What your second finger represents (LHR)

  The direction of the current from positive to negative

  
• Using the LHR to find the direction of force


  The thumb shows the direction of the force on the conductor carrying the current

  
• Factors affecting the size of the force on a conductor in a magnetic field

  the magnetic flux density, the current through the conductor and the length of the conductor
• Magnetic flux density


  A measure of the strength of a magnetic field

  
• F = BIl


  The equation linking force, magnetic flux density, current and length

  
• F


  The symbol for force

  
• B


  The symbol for magnetic flux density

  
• I


  The symbol for current

  
• l

  The symbol for length
• Newtons (N)

  The SI unit for force

  
• Tesla (T)


  The SI unit for magnetic flux density

  
• Amps (A)


  The SI unit for current

  
• Metres (m)


  The SI unit for length