SSC JE Electrical Engineering 2012 Paper

The total impedence of the series LCR circuit is given as
$\mathit{Z}=\mathit{R}+\mathit{j}\left({\mathit{x}}_1-{\mathit{x}}_2\right)$
whole ${\mathit{x}}_1$ is inductive rectance and ${\mathit{x}}_2$ is capacitive reactance.
At a particular frequency (resonant frequency).
We find that ${\mathit{x}}_1={\mathit{x}}_2$ because resonance of a series RLC circuit occurs when the inductive and capacitive reactances are equal in magnitude but cancel each other because they are 180 degrees apart is phase angle between voltage and current is zero and the power factor is unity.
Reactances are equal in magnitude but cancel each other because they are 180 degrees apart in phase. Therefore, the phase angle between voltage and current is zero and the power factor is unity.
Thus, at the reasonant frequency, the net reactance is zero because ${\mathit{x}}_1={\mathit{x}}_2$. The circuit impedence Z becomes minimum and is equal to the resistance R. "Since the impedance is minimum, the current will be maximum."