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Keys to deal with R, L, and C in an AC-circuit. Across R, voltage and current are in-phase Across L, the current lags behind voltage by 90 o , X L = w L Across C, the current leads voltage by 90 o , X C = 1/ w C. Review of AC-circuit. Also, .
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Keys to deal with R, L, and C in an AC-circuit • Across R, voltage and current are in-phase • Across L, the current lags behind voltage by 90o , XL = wL • Across C, the current leads voltage by 90o , XC= 1/wC Review of AC-circuit Also, • When two elements are in series the same current passing through them • When two elements are in parallel the same voltage across them
R I and V are in-phase C I leads V by 90 degree L I lags V by 90 degree
RLC in series Key: IR, IL, and IC are all in phase DVR ~ R DVL ~ XL DVC ~ XC DVmax ~ Z
Imax IC How do you draw the phasor diagram? IR = IL DVR What if RLC are not in series? Which of the following is true (a) DVc = DVL, IC = IL (b) DVc = DVL, IR = IL (c) DVL = DVR, IR = IL (d) DVc = DVL+ DVR, IC = IL (e) DVc = DVL+ DVR, IR = IL DVL DVc = DVR+ DVL
Power dissipation • Only R dissipates power P = I *DV, always For L and C, I and DV are 90o out of phase PL = 0, PC = 0 For R, I and DV are in-phase PR = IDV = Irms2R