Question

The power factor is an L-C-R circuit at resonance is

• A. $0$
• B. $1$
• C. $0.8$
• D. $\frac{1}{2}$

Answer 1

The correct option is B $1$

Power factor is defined as $\cos \varphi$ where $\tan \varphi =\frac{\omega L-\frac{1}{\omega C}}{R}$
At resonance, $\omega L-\frac{1}{\omega C}=0$
$\Rightarrow \tan \varphi =0$
$\Rightarrow \varphi =0$
$\Rightarrow \cos \varphi =1$