1 C = 6.25 X 10

1 A = 1 C/s

electron moves from negative terminal to positive terminal

current moves from higher potential to lower potential

current is an

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.

it is pronounced as

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

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

v in m/s

B in T (tesla)

L in m

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

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

the induced emf in a circuit equals the negative of the time rate of change of magnetic flux thru the circuit

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

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

Left Hand Rule : thumb = electron ( based on ELECTRON FLOW THEORY )

Right Hand Rule : thumb = current ( based on CONVENTIONAL FLOW THEORY )

other fingers = magnetic field

it must be right-hand-thread !

DC :

V = I R

AC :

V = I Z ( magnitude )

Ø

DC :

the algebraic sum of voltages around a closed path of circuit is zero @ ∑ V

AC :

the phasor sum of voltages around a closed path of circuit is zero @ ∑ Ø

DC :

the algebraic sum of currents at a junction of circuit is zero @ ∑ I

AC :

the phasor sum of currents at a junction of circuit is zero @ ∑ Ø

DC :

R

I

AC :

Z

I

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

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

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

R

1 / R

1 / C

C

L

1 / L

Z = R ± jX

Z

Z

Z

the V across

the V across

the V across

Z = impedance

R = resistane

X = reactance

Ø = power factor angle @ impedance angle

S = apparent power ( kVA )

P = real power ( kW )

Q = reactance power (kVAR)

Ø = power factor angle @ impedance angle

cos Ø is called the power factor ( PF )

low PF is due to large Ø , either lead / lag

in a leading circuit ( leading PF ; I leads V by Ø ), the load is primarily

in a lagging circuit ( lagging PF ; I lags V by Ø ), the load is primarily

when a circuit is

when a circuit is

V

I

V

I

S

P

the

the

Y : I

Δ : I

the

the

Y : V

Δ : V

S

P

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

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 !

V

V

step-down transformer is analogous to speed-increasing gearbox :

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

aka

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