 #1
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 Homework Statement:
 An alternating emf source with a variable frequency fd is connected in series with a 40.0 Ω resistor and a 29.0 μF capacitor. The emf amplitude is 11.9 V. Consider a phasor diagram for phasor VR (the potential across the resistor) and phasor VC (the potential across the capacitor). (a) At what driving frequency fd do the two phasors have the same length? At that driving frequency, what are (b) the phase angle in degrees, (c) the angular speed at which the phasors rotate, and (d) the current amplitude?
 Relevant Equations:

ℰ=ℰm*sin(ωdt) ; XC=1/(ωd*C) ; Z=sqrt(R^2+(XLXC)^2)
i=I*sin(ωdt ϕ) ; VL= I*XL ; tanϕ= (XLXC)/R
VR= I*R ; XL=ωd*L
VC=I*XC ; I=ℰ/Z
Using the givens I found ωd=862 rad/s, and with some help I got tanϕ=1 and Z=56.5685 ohms.
But I can't figure out any of the other variables. I'm not even exactly sure what "driving frequency" is and I can't find an equation for it.
But I can't figure out any of the other variables. I'm not even exactly sure what "driving frequency" is and I can't find an equation for it.