266 Alternating Current CircuitsQ33.8The voltages are not added in a scalar form, but in a vector form, as shown in the phasor diagramsthroughout the chapter. Kirchhoff’s loop rule is true at any instant, but the voltages across differentcircuit elements are not simultaneously at their maximum values. Do not forget that an inductor caninduce an emf in itself and that the voltage across it is 90° aheadof the current in the circuit in phase.Q33.9In an RLC series circuit, the phase angle depends on the source frequency. At very low frequencythe capacitor dominates the impedance and the phase angle is near –90°. The phase angle is zero atthe resonance frequency, where the inductive and capacitive reactances are equal. At very highfrequencies φapproaches +°90 .Q33.10−°≤≤ °9090. The extremes are reached when there is no significant resistance in the circuit.Q33.11The resistance remains unchanged, the inductive resistance doubles, and the capacitive reactance isreduced by one half.
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .