How is the phase angle between voltage V and total current I_S in a parallel RLC circuit determined?
Answer & step-by-step solution
Correct answer: D. From the angle between V and the vector sum of I_R, I_L, and I_C
Quick explanation
In a parallel RLC circuit the source current is the phasor sum of I_R, I_L and I_C. The phase angle is the angle between the common voltage and that resultant current.
I_S = I_R + j(I_C − I_L)
tan φ = (I_C − I_L) / I_R
Branch phasors
All branches share V. I_R is in phase with V, I_L lags by 90°, I_C leads by 90°.
Source current
The supply current is the vector sum: I_S = I_R + j(I_C − I_L), so tan φ = (I_C − I_L)/I_R.
Sign of the angle
I_C > I_L → current leads; I_L > I_C → it lags; at resonance they cancel and current is in phase.
Exam tipIn parallel AC circuits add branch currents as phasors, not as plain numbers.
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