At $\omega=1000$ rad/s, inductive reactance is $\omega L=100$ Ω and capacitive reactance is $1/(\omega C)=100$ Ω. They cancel, leaving purely resistive impedance 100 Ω. The source RMS voltage is 100 V because its peak is $100\sqrt2$ V. Thus RMS current is $100/100=1$ A.
More AC circuits and resonance: Peak, average and rms values, apparent, active and reactive power, power factor, phasor analysis, impedance and admittance, series and parallel resonance, locus diagrams, basic filters with R, L and C elements questions
GATE 2020 IN Q44– A balanced 400 V line-voltage three-phase supply feeds the shown unbalanced star: 300 Ω…