• Power expressed in Watts = Power consumed, used or dissipated. Referred to as the True Power.

• Power expressed in Voltamps = Power available to use. Referred to as the Apparent Power. You will find it used to express the size of transformers.

• KVA = Kilovoltamps = Thousand Voltamperes

• Voltage E = Electromotive force. The force necessary to cause the flow of electrical current through a conductor. This current will follow the path of least resistance.

• Current I expressed in Amperes or Amps = The intensity of the flow of electrons through a conductive path.

• Resistance expressed in Ohms = The resistance or opposition to the flow of electrons through a conductive path.

• To find the Voltage E (electromotive force) in volts of a circuit you can multiply the Resistance R ( in Ohms) times the current I (intensity) in Amperes or, you can divide the Power in Watts by the (I) current in Amperes or Amps. Also you can find the square root of the Power (watts) or Voltamps (VA) times the Resistance.

• If you need to know the Resistance in Ohms you can divide the Voltage (E) by the Current (I) in Amperes or, divide the square of the voltage by the Power in Watts or Voltamps, or you can divide the Power in watts by the square of the current in Amps.

• If it is the Current in Amperes or the I (Intensity) that you need to know then you can divide the Power in Watts or Voltamps by the Voltage or, you can divide the Voltage ( E ) by the Resistance ( Ohms ) or find the square of the Watts ( power ) divided by the Resistance ( Ohms ).

• If it is the Power or Watts of a circuit that you need to know then you can find it by multiplying the Resistance in Ohms times the Current I in amps squared, or by multiplying the Voltage times the Current or by dividing the square of the Voltage by the Resistance.

• Power Factor = The ratio of True Power ( Watts ) to Apparent Power (Voltamps). The Power Factor of a circuit is equal to the Watts (True Power) divided by the Voltamps or the Watts divided by the Voltage times the Current (I). Pf = watts divided by volts times amps. Power factor is expressed in percent as in: This circuit has a power factor of 90 percent.

• Reactive Power is a result of Reactance in an AC circuit. The amount of Reactive Power is equal to the square root of the Apparent Power (voltage times amps) squared minus the True power (Watts) squared. The answer is expressed in VARs or Volt Amps Reactive.

The formula above is actually the triangle formula where A squared plus B squared equals the square of C and C squared minus A or B squared equals the square of A or B. This formula is called the Vector Sum formula. Therefore reactive power is the Vector Sum of the Voltage and the Current.

• Reactance (X) is the reactance of the current to Inductance and Capacitance in an AC circuit. Obviously there are two kinds of reactance, Inductive reactance caused by inductance in an AC circuit and Capacitive reactance caused by the Capacitance of an AC circuit. This is what causes the Power factor to be less than 100 percent. Reactance causes the Current to either lead the voltage or lag behind the voltage.

Eli the Ice man tells me that the voltage (E) leads the current (I) in an Inductive circuit and the Current (I) leads the voltage (e) in a capacitve circuit.

• Impedance( Z): In a purely resistive circuit such as a DC ( direct current ) circuit, you can use Ohms law and the Resistance formulas, but in an AC ( Alternating Current ) circuit the opposition to the flow of current is called Impedance. The symbol for Impedance is Z . To use Impedance in the Ohms law formulas replace the R for resistance with the Z for Impedance. In other words Impedance is equal to the Voltage divided by the Current (I) Amps.

• Inductive Reactance ( XL) is equal to 2 Pi F L where 2 Pi is 3.14 times 2 or 6.28 and F is the frequency (example 60 cycle or Hertz) and L is the Inductance

• Capacitive Reactance (XC) is equal to the reciprocal of 2 Pi F C or one over 2pifc or 1 divided by 2pifc.

• Capacitance (C), The capacitance of a capacitive circuit is equal to 1 over 2pifXc.

• Frequency (F): The frequency is equal to 1 over 2pi XcC or one over 2 times pi times the capacitive reactance times the capacitance.

• Triangles: The triangle formula ( I call it ) or the Vector sum formula says that of the three sides if you know any two the other can be found. To find the long side which is C or the hypotenuse, you add A squared plus B squared, the square root of the answer is C. To find either of the other two you take the square of C and subtract either the square of A or B, the answer is the squareroot of the other.