Question

What is the phase angle in a series RLC circuit at resonance? (a) 180° (b) 90° (c) 0 (d) -90° (e) None of those answer is necessarily correct.

Answer 1

The phase angle $\phi$ in series RLC circuit is given by

$$\phi=tan^{-1}\left(\frac{X_L-X_C}{R}\right)$$

Here $X_L\ and \ X_C$ are the reactances of the inductor and capacitor respectively.

At resonance $X_L=X_C$

$$\therefore \phi=tan^{-1}(0)=0$$

Answer: Phase angle at resonance = 0