Formula Page

On this page are listed Tesla coil formulas for a reference to those who prefer to make calculations on paper. Below is a table of formulas on this page.



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 = capacitive reactance in ohms
F = frequency in hertz
C = capacitance in farads


Inductive Reactance



XL = inductive reactance in ohms
F = frequency in hertz
L = inductance in henrys


Resonant Circuit Formula





F = frequency in hertz
L = inductance in henrys
C = capacitance in farads


Spiral Coil Inductance



L = inductance of coil in microhenrys (H)
R = average radius of the coil in inches
N = number of turns
W = width of the coil in inches
 


Helical Coil Inductance



L = inductance of coil in microhenrys (H)
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 = inductance of coil in microhenrys (H)
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 = self capacitance in picofarads
R = radius of secondary coil in inches
L = length of secondary coil in inches

 

Toroid Capacitance

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 = capacitance in picofarads
R = radius in inches


Plate Capacitors



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)


Leyden Jar Capacitors



C = capacitance in microfarads
K = dielectric constant
D = diameter of jar in inches
H = height of jar in inches
T = thickness of jar in inches


AC RMS and Peak Voltage

ERMS = 0.7071E P

ERMS = RMS voltage
EP = peak voltage


Rotary Spark Gap Firings per Second



F = firings per second (hertz)
R = motor RPM rating
E = number of rotary electrodes


Rotary Spark Gap Electrode Speed



S = electrode speed (MPH)
R = motor RPM rating
D = diameter of electrode placement circle (inches)


Energy for L and C

Capacitance Inductance
J = 0.5 V2 C J = 0.5 I2 L

J = joules of energy stored
V = peak charge voltage
I = peak current
C = capacitance in farads
L = inductance in henries

Peak values of V and I are stated in order to emphasize not to use RMS values. The energy stored at any given time is of course: J(t) = 0.5 [V(t)]2 C and J(t) = 0.5 [I(t)]2 L.