In the series LCR circuit as shown in figure, the heat developed in 80 seconds and amplitude of wattless current is:

Heat =irms2⋅Rtirms=i02=25Z2 where, Z=R2+xL−xC2=42+(7−4)2=5Ω⇒ Heat =25522×4×80=4000J and Amplitude of wattless current = i0sin⁡ϕwhere; ϕ=tan−1⁡xL−xCR=tan−1⁡7−44=37∘⇒Amplitude =i0sin⁡37∘=255×35=3 ampere