Alternating Current Flashcards
What is the growth of current in a conductor I?
I= I₀(1-e^-RT/L)
What is the decay of current in a conductor I=?
I= I₀e^-RT/L
What is the charging of a capacitor q=?
q= q₀(1-e^-t/RC)
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
What is the RMS value of alternating current ?
I(v)= I₀/√2=0.707I₀ ;I(v)= root mean square value of current
What is the Impedance of an AC current Z=?
Z= √[R²+(XL-XC)²]
; XL= Inductive reactance
XC= capacitive reactance
Z= Impedance
What is Inductive reactance XL=?
XL= ωL=2πfL=2πL/T
; L= Inductance
T= Time period of AC
What is Capacitive Reactance XC=?
XC= 1/ωC=1/2πfC=T/2πC
; C= Capacitance
T= Time period of AC
What is Average power in AC circuit P(avg)=?
P(avg)= V(rms) i(rms) cos #= Vi/2 cos #
; cos #=Power Factor=R/Z
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
What is Average power delay P in purely resistive circuit =?
P= E(v).I(v)
cos #= 1
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
What is Average power delay P in purely inductive circuit =?
P=0
cos #=0
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
What is Average power delay P in purely capacitive circuit =?
P=0
cos #=0
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
What is Impedance Z of a RC circuit =?
Z= √R²+(1/ωC)²
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
What is Alternating emf E and alternating current for LCR circuit =?
E= E₀ sin ωt
I= I₀ sin (ωt+#)
I lags/leads E by #
What is Average power P at LCR circuit =?
P= E(v)I(v) cos #
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
For parallel resonance circuit , XL=XC and Z is ?mum and I is ?mum
Z is maximum
I is minimum
What is Induced emf e produced by an AC generator =?
e= NBA ω sin ωt= e₀ sin ωt
What is Torque in a DC motor =?
Torque = NBIA sin #
; A= Area of armature
N= No of turns of conductor
B= magnetic field
In a transformer , if energy loss =0, then what is K=?
K= N(s)/N(p)= E(s)/E(p)= I(p)/ I(s)
In transformer , if energy loss !=0 then what is K=?
K=N(s)/N(p)=E(s)/E(p)!=I(p)/I(s)
For step up transformer what is K=?
K>1
For step down transformer what is K=?
K<1
