Ohm's Law Formulas for D-C Circuits.
Ohm's Law Formulas for A-C Circuits.
In these formulas 
is the angle of lead or lag between
current and voltage and cos = P/EI = power factor.
Resistors in Series: Rtotal = R1 + R2 + R3 + . . . .
Two Resistors in Parallel
Resistors in Parallel, General Formula
Sinusoidal Voltages and Currents
| Effective value | = | 0.707 x peak value | |
| [Also known as Root-Mean Square (RMS) value] | |||
| Half Cycle Average value | = | 0.637 x peak value | |
| Peak value | = | 1.414 x effective value | |
| Effective value | = | 1.11 x average value | |
Resonant Frequency Formulas:
*Where in the second formula f is in kHz and L and C are in microunits.
Conductance
Reactance Formulas
Impedance Formulas
Q or Figure of Merit 
Power Factor pf = cos , where is the angle of lead or lag
Note: Active power is the "resistive" power and equals the equivalent heating effect on water.
Three-phase AC Configurations (120 deg phase difference between each voltage)
If the connection to a three phase AC configuration is miswired, switching any two of the phases will put it back in the proper sequence. Electric power for ships commonly uses the delta configuration, while commercial electronic and aircraft applications commonly use the wye configuration.
Voltage/Current Phase Rule of Thumb: Remember "ELI the ICE man"
ELI: Voltage (E) comes before (leads) current (I) in an inductor (L)
ICE: Current (I) comes before (leads) Voltage (E) in a capacitor (C)
Color Code for Resistors
| First and second band: (and third band # of zeros if not gold/silver) | Third band Multiplier | Fourth band Tolerance | |||||
| 0 | Black | 5 | Green | 0.1 | Gold | 5% | Gold |
| 1 | Brown | 6 | Blue | 0.01 | Silver | 10% | Silver |
| 2 | Red | 7 | Violet | 20% | No color | ||
| 3 | Orange | 8 | Gray | ||||
| 4 | Yellow | 9 | White | ||||
The third color band indicates number of zeros to be added after figures given by first two color bands. But if third color band is gold, multiply by 0.1 and if silver multiply by 0.01. Do not confuse with fourth color-band that indicates tolerance. Thus, a resistor marked blue-red-gold-gold has a resistance of 6.2 ohms and a 5% tolerance.
| Color Code for House Wiring: | PURPOSE: | Color Code for Chassis Wiring: | ||
| Black or red | HOT | Red | ||
| White | NEUTRAL (Return) | White | ||
| Green or bare | GROUND | Black |