I have a derivation from a book that says Q = 2π Es / Ed Where Es is the energy stored in the resonant components. Dividing both by the period at resonance gives... Q = ωo Es / Pd This is where I'm stuck. The book says Es = 1/2 LI^2 at the instant that all of the energy is being stored in the inductor. Then it goes on to say the power dissipated in the series resistance, Pd is equal to 1/2 I^2 R. Why is it the average power? Of course these both simplify down to ωoL/R. And, how do you go from 1/2 LI^2 as the energy of the inductor to ωLI^2 as the power? The power is 4πf times the energy? I think I posted this in the wrong section, sorry.