Electromagnetism

• Magnetic fields go from North to South

  Arrow represents the direction at which free north pole would move

  equally spaced and parallel lines show a uniform field
• Flemings left hand rule

  ThuMb = Force

  First Finger = Field

  SecCond finger = Current
• F = B * I * L

  B = magnetic flux density

  I = Current

  L = length
• For a charged particle in circular motion

  Magnetic force = Centripetal force

  B * I * L = M * v^2/ r

  r = M * v / B * Q
• Magnetic Flux = B * A * cos(0)

  B = Magnetic flux density

  A = area

  angle is between the field and the normal
• Magnetic flux linkage =

  Number of coils * Magnetic flux

  Number of coils * B * A * cos(0)
• Faradays law :

  The induced Emf is directly proportional to the rate of change in magnetic flux linkage

  
• Lenz's law:

  The direction of the induced current is so to oppose the change producing it (-)
• Transformers:

  Ac current produces a rate of change of magnetic flux linkage

  A soft iron coil links the primary coil to the secondary coil

  Emf is induced in the secondary coil via faradays law
• Transformers

  Ns/Np = Vs/Vp = Ip/ Is