Question

An ac source of variable frequency $f$ is connected to an $LCR$ series circuit. Which one of the graphs in figure represents the variation of current $I$ in the circuit with frequency $f$ ?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

Current in $LCR$ circuit is $I=V/Z$,
Let $f_f$ be resonant frequency
For frequency $0-f_f$, $Z$ decreases and $I$ increases.
For frequency $f_f-\infty$, $Z$ increases and $I$ decreases.