OHMS Law represents the working relationship between current (amps), Voltage(volts), Resistance(OHMS), and Power(watts) by means of various algebraic formulas.

  • Amps =(Watts / Ohms)
  • Amps = Volts / Ohms
  • Amps = Watts / Volts
  • Ohms = Volts2 / Watts
  • Ohms = Watts / Amps2
  • Ohms = Volts /Amps
  • Volts = Watts / Amps
  • Volts =(Watts * Ohms)
  • Volts = Amps * Ohms
  • Watts = Volts * Amps
  • Watts = Volts2 / Ohms
  • Watts = Amps2 * Ohms

The last goal is learning to make basic electrical calculations through the use of simple formulas.  These formulas are: Amps X Volts = Watts and Amps = Watts % Volts.  By using the following formulas we can make rough estimates regarding the capacities and capabilities of a circuit or power supply source.  Most of the time we are trying to determine the amperage available for use from a power source.   

For instance if we wanted to figure out how many amps of 120V are available for use from a 5000 watt generator, we could use this algebraic formula to determine the ampere capacity.

Amps    X      Volts         =         Watts


Amps    =     Watts          ÷        Volts


Amps    =        5000         ÷        120


41.67    =         5000         ÷        120

Beware, learning these formulas does not make you an electrical engineer overnight.  These calculations do not take into consideration the resistance created from: temperature, conductor length or diameter, plug and receptacle connections, or any other variables which may contribute to voltage drop across the circuit. These are general estimates based on a sterile environment. However, once you have conquered the comprehension of these basic terms and formulas, you are on your way to understanding our distribution systems.  The next step is to understand why electrical safety is important and how it is implemented on the jobsite.