BASIC CONCEPT
1 C = 6.25 X 1018 electrons
1 A = 1 C/s

DIRECTION OF ELECTRON & CURRENT
electron moves from negative terminal to positive terminal
current moves from higher potential to lower potential
current is an imaginary movement of electron


VOLTAGE POLARITY & CURRENT DIRECTION
it results from the fact that an electrical circuit has a negative pole and a positive pole. DC flows in one direction, resulting in a constant polarity. AC flows half the time in one direction and half the time in the other, changing its polarity 100 times per second with 50 Hz current.

CLASSICAL EMF
emf is the abbreviation of electromotive force
it is pronounced as ee-em-eff
it is the influence that makes electric charge move from lower to higher potential
it is a lousy name cos' it is not actually a force
let's put is this way :
a battery with an emf of 3V ( 3J/C ) does 3J of work on every electric charge that passes thru it

MOTIONAL EMF
v in m/s
B in T (tesla)
L in m


COULOMB'S LAW + GAUSS'S LAW
both are fundamental concept of electrostatics ; they are expressing the relationship between electric charge and electric field; Gauss's Law is meant for highly symmetric charge distribution

THE LAW OF BIOT & SAVART + AMPERE'S LAW
both are fundamental concept of magnetics ; they are expressing relationship between magnetic field and its source; Ampere's Law is meant for highly symmetric current distribution

FARADAY'S LAW OF INDUCTION
the induced emf in a circuit equals the negative of the time rate of change of magnetic flux thru the circuit


LENZ'S LAW
the direction of any magnetic induction effect is such as to opposite the cause producing it
let's put it this way :
as the North Pole of the permanent magnet move towards left , the induced current has the direction that produces a North Pole at the right side of the coil to oppose the motion of the permanent magnet


FLEMING
thumb = thrust
index finger = magnetic field
middle finger = current
Fleming's Left Hand Rule is for motor
Fleming's Right Hand Rule is for generator
remember analytical guy does the job; imaginary guy consume the result !


MAGNETIC POLARITY
Left Hand Rule : thumb = electron ( based on ELECTRON FLOW THEORY )
Right Hand Rule : thumb = current ( based on CONVENTIONAL FLOW THEORY )
other fingers = magnetic field


MAXWELL'S CORK SCREW RULE
it must be right-hand-thread !

OHM'S LAW
DC :
     V = I R
AC :
     V = I Z               ( magnitude )
     V = I + Z     ( angle )

KIRCHHOFF'S VOLTAGE LAW ( KVL )
DC :
     the algebraic sum of voltages around a closed path of circuit is zero   @   ∑ Vi = 0
AC :
     the phasor sum of voltages around a closed path of circuit is zero   @   ∑ V = 0

KIRCHHOFF'S CURRENT LAW ( KCL )
DC :
     the algebraic sum of currents at a junction of circuit is zero   @   ∑ Ii = 0
AC :
     the phasor sum of currents at a junction of circuit is zero   @   ∑ I = 0

SOURCE TRANSFORMATIONS, THVENIN'S THEOREM & NORTON'S THEOREM
DC :
     Rno = Rth
     Ino = Isc = Vth Rth
AC :
     Zno = Zth
     Ino = Isc = Vth Zth


MESH ANALYSIS
1) for closed-path that contains nothing inside its interior
2) direction of current preferably clockwise
3) preferably all current sources being transformed into voltage sources
4) voltage drop across all resistors = voltage raise across all voltage sources

LOOP ANALYSIS
1) for any closed-path
2) direction of current can be clockwise or anticlockwise
3) no need to transform current sources into voltage sources
4) voltage drop across all resistors = voltage raise across all voltage sources

NODAL ANALYSIS
1) preferably all voltage sources being transformed into current sources
2) preferably all resistance R being converted into conductance G
3) preferably the bottom node is selected as ground node

EQUIVALENCE OF THE 3 ANIMALS
Req = R1 + R2 + R3 + . . . . . . . .                      (in series)
1 / Req = 1 / R1 + 1 / R2 + 1 / R3 + . . . . . . . .   (in parallel)
1 / Ceq = 1 / C1 + 1 / C2 + 1 / C3 + . . . . . . . .   (in series)
Ceq = C1 + C2 + C3 + . . . . . . . .                      (in parallel)
Leq = L1 + L2 + L3 + . . . . . . . .                      (in series)
1 / Leq = 1 / L1 + 1 / L2 + 1 / L3 + . . . . . . . .   (in parallel)

THE 3 ANIMALS IN A SIMPLE AC CIRCUIT
Z   = R ± jX
ZR = R + j0
ZC = 0 - jXC          where   XC = 1 ( ω C )
ZL = 0 + jXL          where   XL = ω L
the V across pure resistor is in phase with I
the V across pure capacitor lags the I by 90o
the V across pure inductor leads the I by 90o

IMPEDANCE TRIANGLE
Z = impedance
R = resistane
X = reactance
= power factor angle @ impedance angle


POWER TRIANGLE
S = apparent power ( kVA )
P = real power ( kW )
Q = reactance power (kVAR)
= power factor angle @ impedance angle


POWER FACTOR
cos is called the power factor ( PF )
low PF is due to large , either lead / lag
in a leading circuit ( leading PF ; I leads V by ), the load is primarily capacitive in nature
in a lagging circuit ( lagging PF ; I lags V by ), the load is primarily inductive in nature
when a circuit is capacitive, induction motor can be connected in parallel with the load to decrease the
when a circuit is inductive, capacitor bank can be connected in parallel with the load to decrease the

1-PHASE AC
Vav   ≈   0.637 Vp
Iav   ≈   0.637 Vp
Veff   =   Vrms   =   Vp 2   ≈   0.707 Vp
Ieff   =   Irms   =   Ip 2   ≈   0.707 Vp
S1   =   Vp Ip   =   Vrms Irms   =   Irms2 R   =   Vrms2 / R
P1   =   ( Vp Ip ) cos   =   ( Vrms Irms ) cos   =   ( Irms2 R ) cos   =   ( Vrms2 / R ) cos

3-PHASE AC
the line current ( ILI ) is the current carried by the distribution lines ( wires )
the phase current ( IPH ) is the current flowing thru each of the 3 separate loads ( phase )
Y :      IPH   =   ILI
Δ :      IPH   =   ILI 3
the line voltage ( VLI ) is the voltage across 2 terminals, aka terminal voltage @ line-to-line voltage
the phase voltage ( VPH ) is the voltage across each of the 3 separate loads ( phase )
Y :      VPH   =   VLI 3
Δ :      VPH   =   VLI
S3   =   3 VPH IPH   =   3 VLI ILI
P3   =   ( 3 VPH IPH ) cos   =   ( 3 VLI ILI ) cos

SPECIFICATION
our 240V in Malaysia is a RMS voltage
our 380V in Malaysia is a RMS line voltage
our 415V in Malaysia is a RMS line voltage
a 415V ( Y ) motor can be connected as a 240V ( Δ ) motor
a 720V ( Y ) motor can be connected as a 415V ( Δ ) motor

WIRING OF 3-PHASE AC MOTOR
the color code in Malaysia :
L1 = Red
L2 = Yellow
L3 = Blue
( R1 , S2 , T3 ) is analogous to ( L1 , L2 , L3 ) - upstream
( U , V , W ) is analogous to ( L1 , L2 , L3 ) - downstream
Y connection at terminal :

Δ connection at terminal :

let's warm up :

Y connection beneath terminal :

Δ connection beneath terminal :

how to connect the following 6 stator-windings ( 3-phase clockwise induction motor ) into Y and Δ ?
it is a good exercise for you !

what will happen to each of the following cases and how to prove your answer theoretically ?
another good exercise for you !


TRANSFORMER
VP VS   =   NP NS
VP × IP   =   VS × IS
step-down transformer is analogous to speed-increasing gearbox :

step-up transformer is analogous to speed-reducing gearbox :


EDDY CURRENT
aka Foucault current
it is the induced current ( with flow patterns resemble swirling eddies in the river ) due to rotating metallic element in magnetic field or located near a changing magnetic field

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