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Electrical Information

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Some Useful Information About Electric.

Ampere	The constant current which when flowing through two parallel wires 1 m apart would produce in vacua a force of 2 x 10 -7 N/m	A
Coulomb	The quantity of if electricity when a current of 1 ampere flows for 1 second	C
Volt	The electromotive force or potential difference when a constant current of 1 ampere produces a heat in resistance at the rate of 1 newton-meter (joule)/second	V
Ohm	Is the electrical resistance of a conductor in which a constant curent of 1 ampere flow under a constant voltage of 1 volt	ω
Henry	The inductance in which 1 volt is produced by a currrent changing at the rate of 1 ampere/second	H
Farad	The Capacitance in which 1 couomb is stored for a potential difference of 1 volt	F
Siemens	The unit of electrical conductance S = A / V	S
Joule	The unit of energy work and quantity of heat. the work done when the point of application of a force of 1 newton is displaced through a distance of 1 metre in the direction of the force	J
Watt	The unit of power = t Joule/second	W
Weber	The unit of magnetic flux. The magnetic flux linking a circuit of one turn produces in it an electromotive force of 1 volt as it is reduced to zero at a uniform rate in 1 second	Wb
Tesla	The unit of magnetic flux density. The tesla is equal to 1 weber per square metre of circuit area	T

Ohms law

E = Voltage (Volts)
I = Current (Amperes)
R = Resistance (Ohms)
W = Power (Watts)

E = I x R = Sqrt (W x R) = W / I
I = E / R = Sqrt( W / R) = W / E
R = E / I = W / I2 = E2 / W
W = E x I = E2 / R = I2 x R

General Form of Ohms law
R = ρ . L / A
L = Length (metres),
A = Area (metre2,
ρ = resistivity (ω /metre)

Additive Resistances

Resistors in Series
R_total = R1 + R2 + R3...
Voltage across Resistors in Series
V_total = V_R1+V_R2+V_R3..

Resistors in Parallel
R_total = 1/ (1/R1 + 1/R2 +1/R3...)
The Voltage across Resistors in Parallel is the Same= V

Alternating Current Supplies

Alternating Voltage
e = e_max. sin ω. t = e_max .sin(f.t)
e_max = maximum voltage,
t = time (seconds),
ω = angular velocity rads/sec,
f = frequency (cycles /sec)

The Average value of a sinusoidal alternating quantity is calculated at 0.637x maximum value
The Root Mean Square(RMS) value of a sinusoidal alternating quantity is calculated at 0.707 x maximum value.
The form factor of a wave is the RMS value / Average Value = (for a sinusoidal wave) 1.1
The Peak (Crest) Factor is the Peak Value / RMS value = 1.414

Kirchoffs Laws

Kirchoffs First law.
The total current flowing towards a junction is equal to the total current flowing away from that junction.# i.e the algebraic sum of the currents flowing towards a junction is zero

Kirchoffs Second Law
In a closed circuit the algebraic sum of the products of the current and the resistance of each part of the circuit is equal to the resultant e.m.f in the circuit.