Magnetic fields

• Right hand rule for solenoids

  When the fingers point in direction of the current thumb points in direction of the north pole
• Right hand rule for wires

  When fingers point in direction of the field, thumb points in direction of conventional current
• Magnetic flux density


  The strength of a magnetic field
• Force in a magnetic field equation

  F = BILSinx

  F - force felt on wire

  B - magnetic field strength, flux density

  I - current in the wire

  L - length of wire in magnetic field

  Sinx - the angle between the current and field, when they are at right angles theres a maximum force
• Flemings left hand rule

  FBI

  F - Force, Thumb

  B - Magnetic flux density, Index finger

  I - Current, Middle finger
• Magnetic flux


  The flow of magnetic energy around the magnet, Wb
• Flux equation


  Flux = BA

  B - Flux density

  A - Area through which flux passes
• Charged particles in a magnetic field equation

  Force on a moving charge (Q) = BqVSinx

  For an electron moving at an angle of X to the field of the force is:

  F = BevSinx
• What principle leads to Lenzs law

  Conservation of energy
• Why is a laminated core used in a transformer

  To reduce the heating effect of induced eddy currents
• Eddy current in a transformer

  A current induced by the changing flux in the core
• Lenzs law


  The direction of an induced EMF or current is always in a direction as to oppose the change that caused it
• Faradays law


  The magnitude of an induced EMF is directly proportional to the rate of change of flux linkage