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

Answer

A

Explanation

`Z=sqrt(R^(2)+(X_(L)-X_(C))^(2))=sqrt((4)^(2)+(7-4)^(2))=5 Omega`
`i_(0)=(25)/(5)=5` amp
`H_(AC)=i_("max").^(2)RT=(125xx4xx80)/(2)=4000J`
`cos phi=(R)/(Z)=(4)/(5)` so `phi=37^(@)`
Wattless current
`rArrI_(rms) sin phi=3A`