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RC Circuits - Engineering

Q1:

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°

ANS:C - Z = 150 –90°

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.