AC Theory

AC Theory

1. EMF

   • e=Blv
     • Magnetic flux density - B
     • The length of the conductor in the magnetic field - l
     • The velocity or speed of the conductor through the magnetic field - V
     • e = Volts
     • B = teslas
     • l = metres
     • v = metres/second
   • Generation of an EMF
     • Thumb - direction of motion
       • First finger - Field
         • Second finger - Current

2. Connection of metres

   • Ammeter
     • In series with the circuit
   • Voltmeter
     • In parallel with the system or load
   • Wattmeter
     • Measures the amount of power
   • Ohmmeter
     • Measures the resistance

3. Electro-magnetism

   • Lines of flux
     • Cannot cross
     • Flow externally from North Pole to South Pole
   • Magnets
     • Like poles repel
     • Unlike poles attract
   • Maxwells screw rule
     • The relationship between the direction of the current flowing and the magnetic field produced by that current
   • Relays
     • Solenoids
     • Contactor