Single phase ac systems and basic terminology

Question 1

what is waveform

Answer 1

A periodic waveform is one which repeats itself after
certain time interval.

Question 2

what is a phasor, and what trig identity be used

Answer 2

A Phasor is a rotating vector which effectively
represents a sinusoidal function.

the length of the phasor is its RMS value.

sin (cos to sin+90)

Question 2

when is the sinsodial wave postive and negative or leading or lagging

Answer 2

If φ is positive,(towards left) it leads the reference sine wave
and lags if φ is negative.(towards right)

Question 3

phase of an AC

Answer 3

fraction of time period that elapsed from the last reference chosen

Question 4

phase angle formula and meaning

Answer 4

it is the corresponding electrical angle which has elasped after the quantity has passed through the given/ chosen reference

theta = 2pif*t = wt

Question 5

rms value

Answer 5

equivalent to its DC value
defined on its heating effect

or AC current when it flows through the same resistor for the same period of time as that of steady current(DC) flowing thru same resistor for same period of time as a result same heat is produced known as RMS

Question 6

average current value

Answer 6

2Imax/pi

Question 7

`phasor relationship

Answer 7

magnitude and phase of the quantity

choose the reference

represent the phase relationship

Question 8

what is impedance(Z) basic formula
and phase difference of current and voltage

Answer 8

opposes only AC current
|Z|=|V|/|I|

Xo = I/CW
Z= 1/WC = -jXc
current leads voltage by 90

Question 9

phasor diagram lead angle and lag angles

Answer 9

more anticlockwise from reference, and lag is more clockwise from refereance

Question 10

induction formula (i) and phase difference of I and V

Answer 10

Xl= wL (ohms) (inductance and reactance)
current lags voltage by 90 degree)

Z=V/I=wL

Question 11

(impedance formulas) and phase of I and V
impedance angle also

Answer 11

Z=-j Xc (ohm)
Xc=1/CW

current leads voltage by 90

Question 12

Active power with unit ISA

Answer 12

the power consumed by the load in an AC circuit is called as active power in watts (W) =(Avg Power/true power)

Question 13

Reactive power with unit (Q) ISA

Answer 13

AC power which is not consumed but circulates between the source and the element
represented by Q represented by Visin(theta)

unit (VAR)

Question 14

Apparent power: ISA

Answer 14

the total power exsisting in the AC circuit is called as apparent power represented by S = Vrms = I rms unit VA

Question 15

power factor

Answer 15

ratio of active power to apparent power cos Φ = P/S

Question 16

purel resistive circuits conditions and power factor and formula
which lags i or v

Answer 16

Apparent power(S) = Active both (VI) power(P)
cosΦ =1 also power factor=1
reactive power = 0
both voltage and current are in phase

Question 17

RL
and which lags I or V
and power factor (RL)
formulas of power and phase angle

Answer 17

Active power(P) =
current lags voltage
power factor is btw 0-1
VIcosΦ (active power) ‘
VIsinΦ(Reactive power) ‘+’
tan^-1(X/R)

Question 18

RC
which lags I or V and power factor (RC)

Answer 18

current leads voltage
power factor is btw 0-1
VIcosΦ (active power)
VIsinΦ(Reactive power) ‘-‘
Apparent power=VI
-tan^-1(Xl/R)

Question 19

RL circuit formulas and does I lag or lead

Answer 19

Z=sqrt(R^2+XL^2)
V=I*sqrt(R^2+XL^2))

tan^-1(XL/R)
RL(I lags V in phi)

Question 20

RLC inductive formula and voltage or current leads

Answer 20

Z = sqrt (R^2+(Xl-Xc)^2)
V=IZ
V= I*sqrt(R^2+(Xl-Xc)^2)
phi tan^-1((Xc-Xl/R))
voltages leads current by phi

Question 21

RLC capacitive formula
and power formula and
Φ formula

Answer 21

Z = sqrt (R^2+(Xc-Xl)^2)
Z=(R-j(Xl-Xc)) ohms
phi= tan^-1((Xc-Xl/R))
I leads V by phi
P=VIcosΦ

Question 22

RLC series circuit acting resistive conditions and name of condition and I and V does it lag or lead

Answer 22

Vl=Vc
condition knowas as series resonance
P=VIcosΦ cosΦ=1
I and V are in phase
Φ = 0

Question 23

Pure inductor phase angle and power formulas

Answer 23

Active power = 0
Reactive power = -VI
Apparent power = VI
90 degrees current lags voltage

Question 24

Pure capacitor phase angle and power formulas

Answer 24

Active power = 0
Reactive power =-VI
Apparent power = VI
current leads voltage by 90 degrees

Xc=1/CW

Z=V/I=1/wC=-jXc

Question 25

in case of pure inductor and pure capacitor the average power is

Answer 25

its 0 for both of them
power circulates between the source and element but
is not consume