Resonance occures in a series LCR circuit when the frequency of the applied emf is 1000 Hz.

Options

A. when frequency = 900Hz then the current through the voltage source will be ahead of emf of the source
B. the impedance of the circuit is minimum at `f=1000 Hz`
C. at only resonance the voltages across L and C differ in phase by `180^(@)`
D. if the value of C is double, resonance occurs at `f=2000 Hz`.

Answer

A, B

Explanation

`(f=900Hz) lt (f_(res)=1000Hz), so (X_C)gt(X_L)`, circuit becomes capacitive and current leads emf.
At resistance, impedance is minimum.
Not only at resonance, but at all conditions voltage across L and C differs in phases by `180^(@)` when connected in series.