Electrical Engineering - RC Circuits - Discussion

Discussion :: RC Circuits - General Questions (Q.No.26)

26. 

A capacitor with 150 of capacitive reactance is across an ac source. The impedance, expressed in polar form, is

[A]. Z = 150
[B]. Z = 15090°
[C]. Z = 150 –90°
[D]. Z = 150180°

Answer: Option C

Explanation:

No answer description available for this question.

Satya Prakash said: (Oct 22, 2011)  
Its very simple
1/jwc

Since j is in denominator it will lag by angle=-90degree

Deepesh Soni said: (Apr 5, 2013)  
Current lead in capacitor by 90 so impedance will become -90.

Amit said: (Mar 10, 2014)  
Why it is -90 it should be +90?

Arslan Zahoor said: (Jan 19, 2015)  
Current is leading to voltage 90 degree in capacitor and current is lagging to voltage 90 degree in inductor.

Haris said: (Jan 11, 2020)  
Z = R-jxc as R which is not given, it's negligible
Z = -j150.

-For polar;

r = √ (x^2+y^2),
r = √ (+(-150)^2),
r = 150,

∠= tangent inverse(y/x),
=tan.inv(150),
= 90 = -90 and sign - because in capacitive impedance lags by 90.

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