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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 .
 Fall '11
 Staff
 Physics, Current

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