# All Electrical Engineering Formulas List

## Cable Length from Sag, Span

#### Formula: L = S + ((8 * d2) / (3 * S))

Where,

L = Cable Length
S = Cable Span
d = Cable Sag

## Spring Resonant Frequency

#### Formula:

fres= (1/2)* √(k/M)

Where,

fres = Spring Resonance
k = Spring Constant
M = Spring Mass

## Solenoid Coil Electromagnetic Force

#### Formula:

F = (n x i)2 x magnetic constant x a / (2 x g2)

Where,
F = Force,
i = Current,
g = Length of the gap between the solenoid and a piece of metal,
a = Area
n = Number of turns,
Magnetic constant = 4 x PI x 10-7.

## Capacitor Energy (E) and RC Time Constant

#### Formula:

E = (V² x C) / 2
T = R x C

Where,

E =Stored Energy (Joules),
T = Time Constant (S),
V = Volatge (V) ,
C = Capacitance (uF),

## Physical Properties of Coil / Material

#### Formula Used:

T = bl / d
n = Turns/ T
cd = (2 x n x d) + bd
r = (n x d + bd) / 2
a = PI x r x r
L = (2 x PI x r x n) / 1000
rpm = .0333 *((0.812/2)*(0.812/2))/((d/2)*(d/2))
R = rpm x L
V = R x I
P = V x I

Where,
T = Turns per winding,
bl = Length of Bobbin,
d = Wire Diameter,
n = Number of windings,
cd = Outer diameter of coil,
bd = Diameter of Bobbin,
r = radius of middle of coil,
a = Cross sectional area,
L = Total Length,
rpm = Resistance/meter,
R = Resistance,
V = Voltage at Rated Current,
I = Current,
P = Power at Rated Current,

## Air Core Coil Inductance

#### Formula:

Inductance = ((d2) x (n2)) / (18d + 40l)

Where,
d = Coil Diameter,
l = Coil Length,
n = Number of turns.

## Parallel Resistor

#### Formula Used:

Rp = 1 / ((1/R1) + (1/R2))

Where,
Rp = Total Parallel Resistance
R1 & R2 = Resistors connected in parallel

## Straight Wire Inductance / Inductor

#### Formula:

L= 0.00508 x a x (log(2 x a/d)-0.75)

Where,
L = Inductance,
a,d = Length & Diameter of the wire,

## 8051 PIC Microcontroller (UC) Time Delay

#### Formula Used:

TIC12 = 1 / (mhz / 12)TIC6 = 1 / (mhz / 6)
8-bit Timer Counter Maximum Run-Time for 12 clock = TIC12 * 256 / 1000
8-bit Timer Counter Maximum Run-Time for 6 clock = TIC6 * 256 / 1000
16-bit Timer Counter Maximum Run-Time for 12 clock = TIC12 * 65536 / 1000
16-bit Timer Counter Maximum Run-Time for 6 clock = TIC6 * 65536 / 1000
8-Bit DRT Reload Value for 12 clock = 256 -(DRT / TIC12 * 1000)
8-Bit DRT Reload Value for 6 clock = 256 -(DRT / TIC6 * 1000)
16-Bit DRT Reload Value for 12 clock = 65536 -(DRT / TIC12 * 1000)
16-Bit DRT Reload Value for 6 clock = 65536 -(DRT / TIC6 * 1000)

## Parallel Resistance of Electronic Circuit

#### Formula : Where       R1,R2,...Rn are the individual resistor values
Rtotal is the total resistance value in parallel

## Series Resistor / Resistance

#### Formula: R=R1+R2+R3+.......

Where,

R = Total Resistors value
R1 = Individual Resistors value
R2 = Individual Resistors value
R3 = Individual Resistors value

## Microstrip Transmission Lines Impedance (Z0)

#### Formula:  #### Related Calculator:

Formula: ## Series Capacitor / Capacitance

Formula :
1/CTotal = 1/C0 + 1/C1 + 1/C2 + .... + 1/Cn

Where,
C0,C1,..,Cn are the individual capacitors values
CTotal is the total capacitance value of an electrical circuit

## Parallel Capacitor / Capacitance

Formula :
CTotal = C1 + C2 + C3 + .... + Cn

Where,
C1,C2,..,Cn are the individual capacitors values
CTotal is the total capacitors value in parallel

Using this Online Electrical Calculator the
parallel Capacitors
calculation in a circuit is made easier here.

## Horsepower (HP) and Watts Conversion

#### Formula:

Horsepower (HP) =W/HP

Where,

W = Power in wattsHP = Value of one HP

1 Electrical HP = 746 watts

1 Mechanical HP = 745.69987 watts

1 Metric HP = 735.49875 watts

## Power Factor for AC

#### Formula:

Power factor = kW/√ (kW)2 + (kVAr)2

Where,

kW = Real Power
kVAr = Reactive Power

## Three Phase Transformer Capacity

#### Formula:

V = (k x 1000) / (A x Ph)
A = (k x 1000) / (V x Ph)
k = (Ph x V x A) / 1000

Where,

V = Volt
A = Amps
k = kVA
Ph = 3 phase (√3 = 1.732050808)

## Specific Work of Gas Turbine

#### Formula:

w = K / ((K - 1) * R * T1 * [1 - ((p2 / p1)((K-1)/K))])

Where,

w = Specific Work Gas Turbine
K = Ratio Specific Heat Air
R = Individual Gas Constant
T1 = Absolute Temperature
p1 = Primary Pressure
p2 = Secondary Pressure

## 3 Phase Power by Two Wattmeters Method

#### Formula: P = ( V12 * I2 * cos ( 30 + θ ) ) + ( V13 * I3 * cos ( 30 - θ ) )

Where,

P = Three Phase Power
V12 , V13 = Voltage
I2, I3 = Current
θ = Displacement Angle
cos = Cosine

## Specific Work

#### Formula:

w = (p1 - p2) / ρ
t = (p2 - p1) / ρ

Where,

w = Specific Work of Pump
t = Specific Work of Turbine
p1 = Primary Pressure
p2 = Secondary Pressure
ρ = Density

## AVR Timer

#### Formula:

f = cf / p
o = ttt / tr2
rtt = t - (o * tr2)
rt = ttt / f
nf = f / ttt

Where,

f = Frequency
cf = System Clock Frequency
p = Prescaler Clock Value
o =Overflow Count
tr = Timer Resolution
ttt = Total Timer Ticks
rtt = Remainder Timer Ticks
rt = Real Time
nf = New Frequency

## Young's Modulus Spring Resonant Frequency

#### Formula:

fres = (d / (9* D2 * nf)) * √(G / ρ)

Where,

fres = Spring Resonant Frequency
d = Wire Diameter
D = spring Diameter
nf = Total Number of Coils
G = Youngs Modulus of Material
ρ = Material Density

## Gearbox Ratio

#### Formula:

GF = (eRPM * h * 0.002975) / a
MPH = GF / GR

Where,

GF = Gear Factor
GR = Gear Ratio
eRPM = Engine RPM (Revolution per Minute)
h = Tire Height
a = Axle Ratio
MPH = Miles per Hour

## Power Consumption mAh Calculator

#### Formula:

b = (c / h) * 0.70

Where,

b = Average Current Consumption
c = Battery Capacity
h = Estimated Hours

## Electricity Cost

#### Formula:

Energy Consumed per Day = (p × h) / 1000
Energy Consumed per Month = ((p × h) / 1000) × 30
Energy Consumed per Year = ((p × h) / 1000) × 365
Electricity Cost per Day = ((p × h) / 1000) × r
Electricity Cost per Month =(((p × h) / 1000) × 30) × r
Electricity Cost per Year = (((p × h) / 1000) × 365) × r

Where,

p = Power Consumption
h = Hours of Use per Day
r = Electricity Cost per Unit

## Wire Diameter

#### Formula:

D = 2 × √(A / π)

Where,

D = Wire Diameter
A = Area

## Wire Gauge

#### Formula:

Wire Diameter in AWG = -10 - 20 × log(d)

Where,

d = Wire Diameter
g = Diameter of Wire in Gauge

## Electric Potential Energy

#### Formula: Where,

V = Electric Potential
qN = Charge
ε0 = Permittivity(8.8541878176e-12 F/m)
rN = Point Distant

I = P / V

Where,

I = Current
P = Power Rating
V = Voltage

## Transformer Primary Conductor Size

#### Formula:

δ = I / A

Where,

δ = Conductor Size
I= Current
A = Current density

## Number of Turns in a Transformer Coil

#### Formula:

Te = (1/(4.44 × F × M × A))
T = Te × V

Where,

Te = Turns per Volts
T = Total Number of Turns
M = Magnetic flux
A = Area of Core
F = Operating Frequency
V = Voltage

## Transformer Wire Length

#### Formula:

Total Wire Length = Number of Turns × Perimeter of Bobbin

## Volume of Conductor

#### Formula:

Volume of Conductor = Area × Length

## Weight of Transformer Windings

#### Formula:

Weight of Windings(kg) = Density × Volume(m3)

## NE555 Timer Astable Circuit

#### Formula: f = 1.44 / ((R1 + 2(R2)) × C)
THigh = 0.693 × (R1 + R2) × C
Tlow = 0.693 × R2 × C
d = ( THigh / ( THigh + l )) × 100

Where,

R1 = Resistor 1
R2 = Resistor 2
C = Capacitor
d = Duty Cycle
f = Frequency
THigh = Time High
Tlow = Time Low

## Electrostatic

#### Formula:

p = ε0 × e2 / 2

Where,

p = Electrostatic Pressure
e = Electric Field
ε0 = Electric Constant(8.854×10-12)

## Real and Reactive Power

#### Formula:

For Single Phase
t = v × i × cos(p)
r = v × i × sin(p)

For Three Phase
t = √3 × v × i × cos(p)
r = √3 × v × i × sin(p)

Where,

t = Real power
r = Reactive power
v = Voltage
i = Current
p = Phase Angle

P = V × I
V = P / I
I = P / V

Where,

P = Power
V = Voltage
I = Current

## AC Power

#### Formula:

For Single Phase
P = V × I × cos(θ)
V = P / (I × cos(θ)
I = P / (V × cos(θ)

For Three Phase
P = √3 × V × I × cos(θ)
V = P / (3 × I × cos(θ)
I = P / (3 × V × cos(θ)

Where,

P = Power
θ = Power Factor Angle
V = Voltage
I = Current

## Power Consumption South Africa

#### Formula:

p = (e × t) / 1000

Where,

p = Power Consumption
e = Electricity Usage
t = Total Usage Time

## Copper Loss

#### Formula:

l = (a2 × b) + (c2 × d)

Where,

l = Copper Loss
a = Primary Winding Current
b = Primary Winding Ohmic Resistance
c = Secondary Winding Current
d = Secondary Winding Ohmic Resistance

## Total Luminous Flux

#### Formula:

Ω = 2π(1-Cosθ)
F = ΩIv

Where,

Iv = Maximum Luminous Intensity
θ = Cone Full Angle
Ω = Equivalent Solid Angle
F = Total Luminous Flux

## Coaxial Cable Impedance

#### Formula:

Z = (138 × log10 (d1 / (d2)) / √(R)
F = 11.8 / (√(R) × π × ((d1 + d2) / 2))
T =( (7.354 × R) / (log10(d1 / d2)))/0.3048
D = (140.4 × log10(d1 / d2))/0.3048
V = (1 / √ (R)) × 100

Where,

Z = Impedance
d1 = Dielectric Outer Diameter
d2 = Inner Conductor Diameter
R = Dielectric Constant
F = Cutoff Frequency
T = Capacitance
D = Inductance
V = Velocity of Propagation