21. When the frequency of the source voltage decreases, the impedance of a parallel RC circuit ________.
(a) increases
(b) decreases
(c) does not change
(d) decreases to zero
22. An ac circuit consists of a resistor and a capacitor. To increase the phase angle above 45°, the following condition must exist:
(a) R = XC
(b) R > XC
(c) R < XC
(d) R = 5XC
23. In a parallel RC circuit, there is 100 mA through the resistive branch and 100 mA through the capacitive branch. The total rms current is ________.
(a) 200 mA
(b) 100 mA
(c) 282 mA
(d) 141 mA
24. In a series RC circuit, when the frequency and the resistance are halved, the impedance ________.
(a) doubles
(b) is halved
(c) is reduced to one-fourth
(d) cannot be determined without values
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