Hi,

The necessary condition for resonamce in an LCR Circuit is:

When the circuit allows maximum current for a given frequency of the source of alternating supply for which capacitive reactance  becomes equal to the inductive reactance .The impedance of LCR Circuit is minimum and hence current is maximum.

Hope this helps.

Dear Aspirant,
Electrical resonance is said to take place in a series LCR circuit when the circuit allows maximum current for a given frequency of the source of alternating supply for which capacitive reactance becomes equal to the inductive reactance. The impedance of LCR circuit is minimum and hence current is maximum.

I hope you understand this answer.

All the best