73 + Mcqs in Rc Circuits Page 1 McqOptions

1.	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?
A.	37.9
B.	3.7
C.	14,400
D.	4,800
Answer» B. 3.7

Discussion

2.	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
A.	84.5 mW
B.	845 mW
C.	13 mW
D.	130 mW
Answer» B. 845 mW

Discussion

3.	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 = 0.30° mA, what is the source voltage expressed in polar form?
A.	45.6 V
B.	411.3 V
C.	0.411 V
D.	4.11 V
Answer» E.

Discussion

4.	In a series 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
Answer» E.

Discussion

5.	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
A.	9.2 mA
B.	92 mA
C.	4.6 mA
D.	460 mA
Answer» D. 460 mA

Discussion

6.	In a parallel 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
Answer» E.

Discussion

7.	What is the angular difference between +4 and –4?
A.	30°
B.	90°
C.	180°
D.	270°
Answer» D. 270°

Discussion

8.	In the complex plane, the number 4 + 3 is located in the
A.	first quadrant
B.	second quadrant
C.	third quadrant
D.	fourth quadrant
Answer» B. second quadrant

Discussion

9.	When the frequency of the source voltage decreases, the impedance of a parallel circuit
A.	increases
B.	decreases
C.	does not change
D.	decreases to zero
Answer» B. decreases

Discussion

10.	A 47 resistor and a capacitor with a capacitive reactance of 120 are in series across an ac source. What is the circuit impedance, ?
A.	129
B.	12.9
C.	167
D.	73
Answer» B. 12.9

Discussion

11.	A 6 kHz sinusoidal voltage is applied to a series circuit. The frequency of the voltage across the resistor is
A.	0 Hz
B.	12 kHz
C.	6 kHz
D.	18 kHz
Answer» D. 18 kHz

Discussion

12.	In a series circuit, 12 V is measured across the resistor and 15 V is measured across the capacitor. The rms source voltage is
A.	3 V
B.	27 V
C.	19.2 V
D.	1.9 V
Answer» D. 1.9 V

Discussion

13.	The power factor () indicates how much of the apparent power is true power.
A.	True
B.	False
Answer» B. False

Discussion

14.	Total current in an circuit always leads the source voltage.
A.	True
B.	False
Answer» B. False

Discussion

15.	The impedance of a series circuit varies directly with frequency.
A.	True
B.	False
Answer» C.

Discussion

16.	In an circuit, the impedance is determined by both the resistance and the capacitive reactance combined.
A.	True
B.	False
Answer» B. False

Discussion

17.	In the complex plane, the number 14 – 5 is located in the
A.	first quadrant
B.	second quadrant
C.	third quadrant
D.	fourth quadrant
Answer» E.

Discussion

18.	Referring to Problem 21, what is the phase angle for the circuit?
A.	7.1°
B.	71.5°
C.	1.8°
D.	18.4°
Answer» E.

Discussion

19.	The polar form of a complex number consists of a real part and a part.
A.	True
B.	False
Answer» C.

Discussion

20.	In a lag network, the output voltage lags the input voltage in phase.
A.	rue
B.	alse
Answer» B. alse

Discussion

21.	A 120 Ω resistor is in parallel with a capacitor with a capacitive reactance of 40 Ω. Both components are across a 12 V ac source. What is the magnitude of the total impedance?
A.	7.9 Ω
B.	.7 Ω
C.	4,400 Ω
D.	,800 Ω
Answer» B. .7 Ω

Discussion

22.	Positive numbers can be represented by points to the right of the origin on the horizontal axis of a graph.
A.	rue
B.	alse
Answer» B. alse

Discussion

23.	A filter passes all frequencies.
A.	rue
B.	alse
Answer» C.

Discussion

24.	The resistor voltage is always out of phase with the current.
A.	rue
B.	alse
Answer» C.

Discussion

25.	A 470 Ω resistor and a 0.2 µF capacitor are in parallel across a 2.5 kHz ac source. The admittance, Y, in rectangular form, is
A.	12 Ω
B.	.12 mS + j3.14 mS
C.	.14 mS + j2.12 mS
D.	18.3 Ω
Answer» C. .14 mS + j2.12 mS

Discussion

26.	A 47 Ω resistor and a capacitor with 150 Ω of capacitive reactance are in series across an ac source. The impedance, expressed in rectangular form, is
A.	= 47 Ω + j150 Ω
B.	= 47 Ω - j150 Ω
C.	= 197 Ω
D.	= 103 Ω
Answer» C. = 197 Ω

Discussion

27.	A resistor and a capacitor are in series across a 20 V ac source. Circuit impedance is 4.33 kΩ. Current flow in the circuit is
A.	.2 mA
B.	2 mA
C.	.6 mA
D.	60 mA
Answer» D. 60 mA

Discussion

28.	The polar form of a complex number consists of a real part and a j part.
A.	rue
B.	alse
Answer» C.

Discussion

29.	In the complex plane, the number 14 - j5 is located in the
A.	irst quadrant
B.	econd quadrant
C.	hird quadrant
D.	ourth quadrant
Answer» E.

Discussion

30.	A 47 Ω resistor and a capacitor with a capacitive reactance of 120 Ω are in series across an ac source. What is the circuit impedance, Z?
A.	29 Ω
B.	2.9 Ω
C.	67 Ω
D.	3 Ω
Answer» B. 2.9 Ω

Discussion

31.	An imaginary number is one that exists only in the mind of the mathematician.
A.	rue
B.	alse
Answer» C.

Discussion

32.	A 12 kΩ resistor is in series with a 0.02 µF capacitor across a 1.2 kHz ac source. If the current is expressed in polar form as I = 0.3 ∠0° mA, what is the source voltage expressed in polar form?
A.	5.6 V
B.	11.3 V
C.	.411 V
D.	.11 V
Answer» E.

Discussion

33.	A capacitor with 150 Ω of capacitive reactance is across an ac source. The impedance, expressed in polar form, is
A.	= 150
B.	= 150 ∠90°O
C.	= 150 ∠-90°O
D.	= 150 ∠180°O
Answer» D. = 150 ∠180°O

Discussion

34.	The circuit phase angle is the angle between the total current and the applied (source) voltage.
A.	rue
B.	alse
Answer» B. alse

Discussion

35.	The impedance of a series RC circuit varies directly with frequency.
A.	rue
B.	alse
Answer» C.

Discussion

36.	What is the angular difference between +j4 and -j4?
A.	0°
B.	0°
C.	80°
D.	70°
Answer» D. 70°

Discussion

37.	A 2 kΩ resistor is in series with a 0.015 µF capacitor across a 15 kHz ac source. What is the magnitude of the total impedance and the phase angle?
A.	3.4 Ω and ∠ = -19.5°
B.	07 Ω and ∠ = -19.5°
C.	121 Ω and ∠ = -19.5°
D.	34 Ω and ∠ = -38.9°
Answer» D. 34 Ω and ∠ = -38.9°

Discussion

38.	A 2 kΩ resistor and a 0.002 µF capacitor are in series across an ac source. Current in the circuit is 6.50 mA. The true power is
A.	4.5 mW
B.	45 mW
C.	3 mW
D.	30 mW
Answer» B. 45 mW

Discussion

39.	The complex number 40 ∠ 55° is equivalent to
A.	5 + j55
B.	0 + j40
C.	5.88 + j65.52
D.	2.94 + j32.76
Answer» E.

Discussion

40.	Total current in an RC circuit always leads the source voltage.
A.	rue
B.	alse
Answer» B. alse

Discussion

41.	In the complex plane, the number 14 - j5 is located in the Fourth quadrant
A.	rue
B.	alse
Answer» B. alse

Discussion

42.	The capacitor voltage always leads the current by 90°.
A.	rue
B.	alse
Answer» C.

Discussion

43.	The complex number 6 + j6 is equivalent to
A.	∠45°
B.	6 ∠45°
C.	.48 ∠45°
D.	.48 ∠90°
Answer» D. .48 ∠90°

Discussion

44.	Apparent power is expressed in watts.
A.	rue
B.	alse
Answer» C.

Discussion

45.	A positive angle of 30° is equivalent to a negative angle of
A.	30°
B.	330°
C.	60°
D.	180°
Answer» C. 60°

Discussion

46.	The complex number 40 55¬∞ is equivalent to
A.	55 + j55
B.	40 + j40
C.	45.88 + j65.52
D.	22.94 + j32.76
Answer» E.

Discussion

47.	Complex numbers can be added and subtracted but not multiplied or divided.
A.	1
B.
C.	1
D.
Answer» C. 1

Discussion

48.	For a certain load, the true power is 150 W and the reactive power is 125 VAR. The apparent power is
A.	19.52 W
B.	195.2 W
C.	275 W
D.	25 W
Answer» C. 275 W

Discussion

49.	Point +4 on the complex plane is
A.	4 units above the origin on the j axis
B.	4 units below the origin on the j axis
C.	4 units right of the origin on the real axis
D.	4 units left of the origin on the real axis
Answer» D. 4 units left of the origin on the real axis

Discussion

50.	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
Answer» D. R = 5XC

Discussion

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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?

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A resistor and a capacitor are in series across a 20 V ac source. Circuit impedance is 4.33 kΩ. Current flow in the circuit is

The polar form of a complex number consists of a real part and a j part.

In the complex plane, the number 14 - j5 is located in the

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

An imaginary number is one that exists only in the mind of the mathematician.

A 12 kΩ resistor is in series with a 0.02 µF capacitor across a 1.2 kHz ac source. If the current is expressed in polar form as I = 0.3 ∠0° mA, what is the source voltage expressed in polar form?

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

The circuit phase angle is the angle between the total current and the applied (source) voltage.

The impedance of a series RC circuit varies directly with frequency.

What is the angular difference between +j4 and -j4?

A 2 kΩ resistor is in series with a 0.015 µF capacitor across a 15 kHz ac source. What is the magnitude of the total impedance and the phase angle?

A 2 kΩ resistor and a 0.002 µF capacitor are in series across an ac source. Current in the circuit is 6.50 mA. The true power is

The complex number 40 ∠ 55° is equivalent to

Total current in an RC circuit always leads the source voltage.

In the complex plane, the number 14 - j5 is located in the Fourth quadrant

The capacitor voltage always leads the current by 90°.

The complex number 6 + j6 is equivalent to

Apparent power is expressed in watts.

A positive angle of 30° is equivalent to a negative angle of

The complex number 40 55¬∞ is equivalent to

Complex numbers can be added and subtracted but not multiplied or divided.

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

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An ac circuit consists of a resistor and a capacitor. To increase the phase angle above 45¬∞, the following condition must exist: