In series L−C−R circuit, ‌XL=XC ∴‌‌Z=√R2+(XL−XC)2 ‌=√R2+02 Z‌=R ∴‌ Power factor ‌‌=cos‌φ ‌=‌
R
Z
=‌
R
R
=1 Hence, power factor is not zero. Therefore option (d) is not correct. In L−C−R series resonance circuit, peak energy stored by a capacitor is equal to peak energy stored by an inductor. Average power, Pavg=Vrms×Irms×cos‌0∘ =Vrms×Irms = apparent power L−C−R series resonance circuit is purely resistive because XL=XC, hence no wattless current exists in this circuit therefore wattless current is zero.