A 20.0-mH inductor is connected to a standard electrical outlet (ΔVrms= 120 V; f = 60.0 Hz). Determine the energy stored in the inductor at t = (1/180) s, assuming that this energy is zero at t = 0. Now when i tried to solve it, this is what i did: ω = 2∏ f = 2∏(60.0/s) = 377 rad/s XL = ω L = (377)(0.02)= 7.54 Ω Irms = ΔVrms/XL = 120 V/7.54 Ω =15.9 A Imax= √2Irms= √2(15.9 A) = 22.5 A instantaneous current in the inductor: i(t)=ΔVmax sin(ωt - ∏/2) / ωL i(t)=(120√2) sin(377x(1/180) - ∏/2) i(t)=0.206 A U= L [i(t)]^2 [sin ωt]^2 / 2 U= 0.02 (0.206)^2 [sin (377x(1/180))]^2 / 2 U= 6.76 x 10^-3 J But in the book's solution manual it was solved using the instantaneous current in the resistor, which has the formula: i=Imax sinωt I don't understand why the book used current in the resistor rather than the one in the inductor. Please help me! I would like an explanation to that.