Question

In $L-C-R$ resonant circuit what is the phase angle $\phi$ ?

• A. $90^{\circ}$
• B. $180^{\circ}$
• C. $0^{\circ}$
• D. $60^{\circ}$

Answer 1

Answer: (C)

$0^{\circ}$

Answer 2

In an $L-C-R$ circuit phase angle is defined as
$\cos \phi=\frac{R}{Z}$
where $Z=\sqrt{R^{2}+\left(X_{L}-X_{C}\right)^{2}}$
When circuit is resonant
$X_{L}= X_{C}$
$\therefore Z=R$
So, $\cos \phi=\frac{R}{R}=1$
or $\phi=0^{\circ}$