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 RC Circuits Multiple Choice

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1 .       When the frequency of the voltage applied to a series RC circuit is decreased, the impedance [Hint]

 increases decreases remains the same doubles

2 .       When the frequency of the voltage applied to a series RC circuit is increased, the phase angle [Hint]

 increases decreases remains the same becomes erratic

3 .       In a series RC circuit, when the frequency and the resistance are halved, the impedance [Hint]

 doubles is halved is reduced to one-fourth cannot be determined without values

4 .       In a series RC circuit, 12 V(rms) is measured across the resistor and 15 V(rms) is measured across the capacitor. The rms source voltage is [Hint]

 3 V 27 V 19.2 V 1.9 V

5 .       The voltages in Problem 4 are measured at a certain frequency. To make the capacitor voltage greater than the resistor voltage, the frequency [Hint]

 must be increased must be decreased is held constant has no effect

6 .       An ac circuit consists of a resistor and a capacitor. To increase the phase angle above 45°, the following condition must exist: [Hint]

 R = XC R > XC R < XC R = 5XC

7 .       When the frequency of the source voltage decreases, the impedance of a parallel RC circuit [Hint]

 increases decreases does not change decreases to zero

8 .       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 [Hint]

 200 mA 100 mA 282 mA 141 mA

9 .       A 2 k resistor and a 0.002 F capacitor are in series across an ac source. Current in the circuit is 6.50 mA. The true power is [Hint]

 84.5 mW 845 mW 13 mW 130 mW

10 .       A resistor and a capacitor are in series across a 20 V ac source. Circuit impedance is 4.33 k. Current flow in the circuit is [Hint]

 9.2 mA 92 mA 4.6 mA 460 mA

11 .       For a certain load, the true power is 150 W and the reactive power is 125 VAR. The apparent power is [Hint]

 19.52 W 195.2 W 275 W 25 W

12 .       A 6 kHz sinusoidal voltage is applied to a series RC circuit. The frequency of the voltage across the resistor is [Hint]

 0 Hz 12 kHz 6 kHz 18 kHz

13 .       A 47 resistor and a capacitor with a capacitive reactance of 120 are in series across an ac source. What is the circuit impedance, Z? [Hint]

 129 12.9 167 73

14 .       If the voltage source in Problem 13 has an rms value of 60 V, how much current flows in the circuit? [Hint]

 46.5 mA 465 mA 359 mA 821 mA

15 .       A capacitor with 150 of capacitive reactance is across an ac source. The impedance, expressed in polar form, is [Hint]

 Z = 150 Z = 15090° Z = 150 -90° Z = 150180°

16 .       A 47 resistor and a capacitor with 150 of capacitive reactance are in series across an ac source. The impedance, expressed in rectangular form, is [Hint]

 Z = 47 + j150 Z = 47 - j150 Z = 197 Z = 103

17 .       Referring to Problem 16, the impedance, expressed in polar form, is [Hint]

 157.2072.6° 4772.6° 15072.6° 157.2022.6°

18 .       A 12 k resistor is in series with a 0.02 F capacitor across a 1.2 kHz ac source. If the current is expressed in polar form as I = 0.30° mA, what is the source voltage expressed in polar form? [Hint]

 45.6 V 411.3 V 0.411 V 4.11 V

19 .       Referring to Problem 18, which statement is true? [Hint]

 voltage lags current by 28.9° current lags voltage by 28.9° current and voltage are in phase voltage lags current by 2.89°

20 .       A 2 k resistor is in series with a 0.015 F capacitor across a 15 kHz ac source. What is the magnitude of the total impedance and the phase angle? [Hint]

 73.4 and θ = -19.5° 707 and θ = -19.5° 734 and θ = -19.5° 734 and θ = -38.9°

21 .       A 120 resistor is in parallel with a capacitor with a capacitive reactance of 40 . Both components are across a 12 V ac source. What is the magnitude of the total impedance? [Hint]

 37.9 3.7 14,400 4,800

22 .       Referring to Problem 21, what is the phase angle for the circuit? [Hint]

 7.1° 71.5° 1.8° 18.4°

23 .       A 470 resistor and a 0.2 F capacitor are in parallel across a 2.5 kHz ac source. The admittance, Y, in rectangular form, is [Hint]

 212 2.12 mS + j3.14 mS 3.14 mS + j2.12 mS 318.3

24 .       Referring to Problem 23, what is the admittance, Y, in polar form? [Hint]

 3.785.9° 3.7834° 37.855.9° 37.834°

25 .       Referring to Problem 23, what is the circuit impedance, Z? [Hint]

 264 -55.9° 264 -34° 2.64 -55.9° 2.64 -34°

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