## Most Used Formulas

Resistance Formulas

DIELECTRIC CONSTANTS
In series
In parallel
 Two resistorsin parallel
Kind of                                                Approximate*
Dielectric                                                K Value
 Air (at atmospheric pressure) .................... Bakelite .................................................... Beeswax .................................................. Cambric (varnished) ................................. Fibre (Red) .............................................. Glass (window or flint) .............................. Gutta Percha ............................................ Mica ........................................................ Paraffin (solid) .......................................... Paraffin Coated Paper .............................. Porcelain .................................................. Pyrex ....................................................... Quartz ...................................................... Rubber ..................................................... Slate ......................................................... Wood (very dry) ....................................... 1.0 5.0 3.0 4.0 5.0 8.0 4.0 6.0 2.5 3.5 6.0 4.5 5.0 3.0 7.0 5.0
* These values are approximate, since true values
depend upon quality or grade of material used, as
well as moisture content, temperature and frequency
characteristics of each
Capacitance
In parallel
In series
 Two capacitorsin series

The Quantity of Electricity Stored Within a Capacitor is Given by   Self-Inductance

where   Q = the quantity stored in coulombs,
E = the potential impressed across the
capacitor in volts,
In series
In parallel
 Two inductorsin parallel
The Capacitance of a Parallel Plate
Capacitor is Given by
Coupled Inductance

where   C = capacitance in mmfd.,
K = dielectric constant,
*S = area of one plate in square centimeters,
N = number of plates,
*d = thickness of the dielectric in centimeters
(same as the distance between plates).

*When S and d are given in inches, change
constant 0.0885 to 0.224. Answer will still be