A LCR circuit has L=10mH,R=3Ω, and C=1μF connected in series to a source of 15cos⁡ωt volt . Calculate the current amplitude (in ampere) at a frequency that is 10 % lower than the resonant frequency.

The resonance frequency, ​ωr=1LC=110×10−3×1×10−6​=104rad/s​Thus ,ω=0.90ωr=9×103rad/s​XL=ωL=9×103×(10×10−3)​=90Ω​and  XC=1ωC=19×103×10−6​=111.11Ω​The impedance, Z=R2+(XC-XL)2​=32+(111.11−90)2​=21.32Ω​ The current amplitude, ​i0=V0Z=1521.32=0.704A