Ohm's Law
E = IZ P = IE
E = volts
I = current in amps
Z = impedance or resistance in ohms
P = power in watts
Transformer Input and Output
EPIP = ESIS
EP = primary voltage
IP = primary current in amps
ES = secondary voltage
IS = secondary current in amps
Capacitive Reactance
Xc=1/{92phi)FC}
XC = capacitive reactance in ohms
F = frequency in hertz
C = capacitance in farads
Inductive Reactance
Xl=(2phi)FL
Xl = inductive reactance in ohms
F = frequency in hertz
L = inductance in henrys
Resonant Circuit Formula
(4phi^2)F^2LC=1
F = frequency in hertz
L = inductance in henrys
C = capacitance in farads
Archimedes Spiral Coil Inductance
L2=(NR)^2/{8R+11W}
L2 = inductance of coil in microhenrys (µH)
R = average radius of the coil in inches
N = number of turns
W = width of the coil in inches
Helical Coil Inductance
L1=(NR)^2/{9R+10H}
L1 = inductance of coil in microhenrys (µH)
N = number of turns
R = radius of coil in inches (Measure from the center of the coil to the middle of the wire.)
H = height of coil in inches
Inverse Conical Coil Inductance
L=(sqroot){[L1sinA]^2+[L2cosA]^2}
L = inductance of coil in microhenrys (µH)
L1 = helix factor
L2 = spiral factor
N = number of turns
R = average radius of coil in inches
H = effective height of the coil in inches
W = effective width of the coil in inches
X = rise angle of the coil in degrees
Secondary Coil Dimensions
T = AH
L = length of wire in feet
D = outer diameter of coil form in inches
H = height of windings in inches
A = number of turns per inch
T = total number of turns
B = thickness of wire in inches
Medhurst
C=.29L+.41R+1.94([sqroot]R^3/L)
C = self capacitance in picofarads
R = radius of secondary coil in inches
L = length of secondary coil in inches
Toroid Capacitance
C=1.4(1.2781-{D2/D1})([sqroot][phi]D2(D1-D2))
C = capacitance in picofarads
D1 = outside diameter of toroid in inches
D2 = diameter of cross section of toroid in inches
This equation courtesy Bert Pool.
Sphere Capacitance
C=25.4R/9
C = capacitance in picofarads
R = radius in inches
Plate Capacitors
C=[.224K(N-1)] /[1000000D]
C = capacitance in microfarads
K = dielectric constant
A = area of each plate in square inches
N = number of plates
D = distance between plates in inches (thickness of dielectric)