In the series L – C – R circuit, the voltage across resistance, capacitance and inductance are 30V each at frequency f = f0 .

VL=VC=VR;⇒XL=XC=Rwhen inductor is short circuitedZ=R2+xc2=2R∴I=30Z=302R∴VL=ixL=302R×R=302∴(A) is incorrect and with similar calculations (B) will be correct. Here f0 is the resonance frequency as vL = vC⇒f0=12πLC and ω0=2πf0=1LCxLxC=ωL1/ωC=ω2LC Given f=2f0⇒ω=2ω0∴xLxC=4∴(C) is also correct.