Question

In an R-C circuit, select the correct options among the following :

• A. Instantaneous A.C is given by $I=I_{0}sin(wt+\varphi )$
• B. The alternating current in the circuit leads the emf by a phase angle
• C. Its impedance is $\sqrt{R^2+(wC{)}^2}$
• D. Its capacitive reactance is $\omega C$

Answer 1

Answer: (A), (B)

The correct options are
A The alternating current in the circuit leads the emf by a phase angle
B Instantaneous A.C is given by $I=I_{0}sin(wt+\varphi )$

A, B

Instantaneous current is the current at any instant. In an RC circuit, the instantaneous AC current is given by

$I=I_0\sin (\omega t+\varphi )$

In circuits with primary capacitive loads, current leads the voltage. This is because current must flow to the two plates of the capacitor, where charge is stored. Only after charge accumulates at the plates of the capacitor a voltage difference is established.

$Z=\sqrt{R^2+(\frac{1}{wC}{)}^2}$

$Z_c=\frac{1}{wC}$

current leads by $\frac{\pi }{2}$ in C-R circuit

So Option A and B are correct