Which of the following releations is correct ?

Options

A. Frequency must be increased and current after the change is `10 A`
B. Frequency must be decreased and current after the change is `10 A`
C. Frequency must be decreased and current is same as that of initial value
D. The given information is insufficient to conclude anything.

Answer

A

Explanation

At resonance `X_(L)=X_(C)`
`I_(rms)=V_(rms)/R=10sqrt2`...(i)
When currents lags by `pi/4`:
`I_(rms)=V_(rms)/sqrt(R^(2)+X^(2))V_(rms)/sqrt2R=10A`