Derivations

• A Volt the Electromotive force required to produce an Ampere of current. It is the SI unit of electric potential and is represented by the letter E or V in formulae.
• An Ohm is the resistance to a current flow of 1 Ampere at an EMF of 1 Volt.
• A Watt is the amount of heat produced in a resistance of 1 ohm at a current flow of one amp. It is represented by the letter P in formulae.
• A joule is the amount of heat produced in a resistance of 1 ohm at a current flow of one amp in 1 second. It is the equivalent of 1 watt per second.

• New Zealand Mains Power
  • 240 Volts at 50 HZ
    The voltage is a nomimal value and will vary from area to area and depending upon the electricity usage by the consumers at the time.
• Power factor is the phase relationship between the current and voltage of an alternating supply. Ideally it should be about 0.9

• DC Power: P = E * I where:
  P is measured in Watts,
  E is in Volts,
  I in Amps.
  
• AC Power: P = E * I * pf where:
  pf is the measured power factor

• 1 Milliwatt (mW) = 1/1000 Watts
• 1 Kilowatt (KW) = 1000 Watts.
• 1 Megawatt (MW) = 1000 KW