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Flashcards in Alternating Current Deck (28):
1

What is the growth of current in a conductor I?

I= I₀(1-e^-RT/L)

2

What is the decay of current in a conductor I=?

I= I₀e^-RT/L

3

What is the charging of a capacitor q=?

q= q₀(1-e^-t/RC)

4

What is the Average value of alternating current I(m)=?

I(m)= 2I₀/π=0.637I₀
;I(m)= mean or avg current in one half cycle
I(o)= peak value of Ac

5

What is the RMS value of alternating current ?

I(v)= I₀/√2=0.707I₀
;I(v)= root mean square value of current

6

What is the Impedance of an AC current Z=?

Z= √[R²+(XL-XC)²]
; XL= Inductive reactance
XC= capacitive reactance
Z= Impedance

7

What is Inductive reactance XL=?

XL= ωL=2πfL=2πL/T
; L= Inductance
T= Time period of AC

8

What is Capacitive Reactance XC=?

XC= 1/ωC=1/2πfC=T/2πC
; C= Capacitance
T= Time period of AC

9

What is Average power in AC circuit P(avg)=?

P(avg)= V(rms) i(rms) cos #= Vi/2 cos #
; cos #=Power Factor=R/Z

10

What is Alternating emf E and alternating current for Pure resistive circuit =?

E= E₀ sin ωt
I= I₀ sin ωt
E and I are in the same phase

11

What is Average power delay P in purely resistive circuit =?

P= E(v).I(v)
cos #= 1

12

What is Alternating emf E and alternating current for Pure inductive circuit =?

E= E₀ sin ωt
I= I₀ sin (ωt-π/2)
I lags behind V by π/2
XL= ωL

13

What is Average power delay P in purely inductive circuit =?

P=0
cos #=0

14

What is Alternating emf E and alternating current for Pure capacitive circuit =?

E= E₀ sin ωt
I= I₀ sin (ωt+π/2)
I leads V by π/2
XC= 1/ωC

15

What is Average power delay P in purely capacitive circuit =?

P=0
cos #=0

16

What is Alternating emf E and alternating current for RC circuit =?

E= E₀ sin ωt
I= E₀/Z sin (ωt- δ)
I lags E by δ
XC=1/ωC

17

What is Impedance Z of a RC circuit =?

Z= √R²+(1/ωC)²

18

What is Alternating emf E and alternating current for LC circuit =?

E= E₀ sin ωt
I= E₀/Z sin (ωt- δ)
Z= XL-XC=0

19

What is Alternating emf E and alternating current for LCR circuit =?

E= E₀ sin ωt
I= I₀ sin (ωt+#)
I lags/leads E by #

20

What is Average power P at LCR circuit =?

P= E(v)I(v) cos #

21

What is Frequency f in series resonance circuit at XL=XC, Z=R

f= 1/2π√LC
Q= 1/R (L/C)^-1/2
Impedance minimum , current maximum

22

For parallel resonance circuit , XL=XC and Z is ?mum and I is ?mum

Z is maximum
I is minimum

23

What is Induced emf e produced by an AC generator =?

e= NBA ω sin ωt= e₀ sin ωt

24

What is Torque in a DC motor =?

Torque = NBIA sin #
; A= Area of armature
N= No of turns of conductor
B= magnetic field

25

In a transformer , if energy loss =0, then what is K=?

K= N(s)/N(p)= E(s)/E(p)= I(p)/ I(s)

26

In transformer , if energy loss !=0 then what is K=?

K=N(s)/N(p)=E(s)/E(p)!=I(p)/I(s)

27

For step up transformer what is K=?

K>1

28

For step down transformer what is K=?

K<1