925_Physics ProblemsTechnical Physics

925_Physics ProblemsTechnical Physics - 266 Alternating...

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266 Alternating Current Circuits Q33.8 The voltages are not added in a scalar form, but in a vector form, as shown in the phasor diagrams throughout the chapter. Kirchhoff’s loop rule is true at any instant, but the voltages across different circuit elements are not simultaneously at their maximum values. Do not forget that an inductor can induce an emf in itself and that the voltage across it is 90° ahead of the current in the circuit in phase. Q33.9 In an RLC series circuit, the phase angle depends on the source frequency. At very low frequency the capacitor dominates the impedance and the phase angle is near –90 ° . The phase angle is zero at the resonance frequency, where the inductive and capacitive reactances are equal. At very high frequencies φ approaches 90 . Q33.10 −° ≤≤ ° 90 90 . The extremes are reached when there is no significant resistance in the circuit. Q33.11 The resistance remains unchanged, the inductive resistance doubles, and the capacitive reactance is reduced 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 .

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