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  2. Electrical Formulae

I figured to further our "Codex" of technical information a listing of Electrical Formulae and relationships would be a handy reference for those newer to the wonderful math surrounding electricity.

This is only intended as a handy reference. Indeed the equations in this article are reference, and do not describe the underlying principles of electricity. For those of you interested in Electrical Engineering, a LOT of further instruction is required for proper understanding. Just because you know a formula, does not mean you know how to appropriately apply it in the real world. Please leave electrical work to the professionals.


In the formulae I used "to the power of negative one" instead of the common notation to make it easier. The Equation above shows that they are indeed the same thing. It's just a lot easier to show the formulae on one line of text than two or more.

Letter meanings:

E = EMF or Voltage (In Volts (V))
I = Intensity of Current or Amperes (in Amps (A))
R = Resistance (In Ohms (Ω))
Z = Impedance (In Ohms (Ω)), for RCL circuits
X = Reactance (In Ohms (Ω)), for C and L circuits
P = Power (In Watts (W))
C = Capacitance (In Farads (F)), for capacitors
τ = Time for one Constant in Seconds (for calculating with Capacitance)
L = Inductance (In Henrys (H)), for Inductors
PF = Power Factor (%)
VA or S = Apparent Power
VARs or Q= Reactive Power
Q = Quality of an Inductor, The relationship between the Reactance and Resistance of an Inductor.
Q = Electric Charge in Coulombs (Yes Q is a commonly used letter to many people's annoyance)
f = Frequency (In Hertz (hz))

Electrical Formulae:
Basic:
E=IR
P=IE


Capacitance: (I leads E by 90-degrees)

Q = CV
pC = KA ÷ 4.45 D

Inductance:



This is a work in progress, because just coding it was not going to work on these forums, so I am making a series of images to make the table readable with subscripts.

Calculations for Electronics:

Calculations for Motors:
K1 ... (Will complete later)

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