Electronics - RL Circuits - Discussion

1. 

As frequency increases

[A]. both series and parallel RL impedance decrease
[B]. series RL impedance decreases and parallel RL impedance increases
[C]. series RL impedance increases and parallel RL impedance decreases
[D]. both series and parallel RL impedance increase

Answer: Option D

Explanation:

No answer description available for this question.

Dinesh said: (Sep 22, 2011)  
Xl=2pifl. In both the cases inductive reactance will increase with respect to frequency.

Hence increase in impedence.

Situ Dash said: (Nov 9, 2011)  
In both series & parallel

Xl=2*pi*f*L

So as freq increases Xl value increases & hence impedance increases.

Sri Harshith Rajam said: (Dec 22, 2011)  
Inductive Impedance (X)= Omega*Inductance
As omega is directly proportional to the frequency (2*pi*f) , the impedance increases and the inductor circuit tends to enter into the open circuit state !

Bhanu said: (Apr 22, 2012)  
In parallel the real impedence is in dinominator so optiion c is coorrect.

Jaydeep Gidhvani said: (Jan 10, 2013)  
Z=impedance
Z=R+XL
XL=2*Pi*F*L.

F Increase
XL Increase
SO Impedance increase.

Raheel Ahmed said: (Mar 2, 2013)  
When the frequency of Parallel RL Circuit Increases, XL increases which causes IL (current through inductor) decreases. Decrease in IL causes It (It=Il+Ir) to decrease, which means by relation IT=Vs/Zt, the Zt (Total Impedance) Increases.

Jyothis said: (Sep 12, 2015)  
Find effective impedance of both series and parallel circuits. Analyse what happens when omega increases.

Samurtza said: (Aug 31, 2017)  
Z(w)_Series=R+jwL.
Z(0)_Series= R & |Z(infinite)_Series|= infinite (w increases , |Z| increases in SERIES) [Open at High frequency].

Z(w)_Parallel=1/(1/R-j/wL) .
|Z(0)_Parallel |=infinite & Z(infinite )_Parallel = R ( w increases , |Z| decreases in PARALLEL) [Short at DC].

Samurtza said: (Aug 31, 2017)  
Can be seen via MATLAB (Option C is correct)

w=0:1/10:2*π;
% RL Impedance Increases.

R=1; L=1;
Zs=R+j*w*L;
Zp=1./(1./R+1./j*w*L);
% normalized plots.
plot(w,abs(Zs)/max(abs(Zs)),w,abs(Zp)/max(abs(Zp))).

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