Formulas for Tesla coils

 

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 (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

 

 

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 = 0.7071·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

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.

 

 

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