# Formula Page

On this page I have posted 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

### 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

### Spiral Coil Inductance

 L = 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

 L = 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 = 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 = self capacitance in picofarads
R = radius of secondary coil in inches
L = length of secondary coil in inches

### Toroid Capacitance

D1 = outside diameter of toroid in inches
D2 = diameter of cross section of toroid in inches
This equation courtesy Bert Pool.

### Plate Capacitors

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

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 = 0.7071·E 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