Walker, Halliday & Resnick — Electromagnetic Oscillations and Alternating Current: Problem 12

12 An alternating emf source with a variable frequency \(f_d\) is connected in series with an \(80.0\ \Omega\) resistor and a \(25.0\ \text{mH}\) inductor. The emf amplitude is \(6.00\ \text{V}\). (a) Draw a phasor diagram for phasor \(V_R\) (the potential across the resistor) and phasor \(V_L\) (the potential across the inductor). (b) At what driving frequency \(f_d\) do the two phasors have the same length? At that driving frequency, what are (c) the phase angle in degrees, (d) the angular speed at which the phasors rotate, and (e) the current amplitude?