MULTIPLE CHOICE
1. An ac generator with peak voltage 100 volts is placed across a 10- resistor. What is the average power dissipated? a. 100 W b. 150 W c. 500 W d. 1 000 W e. 2 000 W
ANS: C PTS: 2 DIF: Average
2. An electric heater draws an average power of 1 100 Watts when plugged into a 110 V-rms outlet. Calculate the resistance of the heater and the rms current.
a. 11, 10 A (rms) b. 110, 10 A (rms) c. 10, 11 A (rms) d. 10, 110 A (rms) e. 0.09, 11 A (rms)
ANS: A PTS: 2 DIF: Average
3. An incandescent lightbulb is rated at 100 Watts when plugged into a 110 V-rms household outlet. Calculate the resistance of the filament and the rms current.
a. 12.2, 0.91 A (rms) b. 10, 1.0 A (rms) c. 110, 1.0 A (rms) d. 121, 0.91 A (rms) e. 11, 1.1 A (rms)
ANS: D PTS: 2 DIF: Average
4. A high-voltage powerline operates at 500 000 V-rms and carries an rms current of 500 A. If the resistance of the cable is 0.050/km, what is the resistive power loss in 200 km of the powerline? a. 250 kW
b. 500 kW c. 1 Megawatt
d. 2.5 Megawatts e. 250 Megawatts
ANS: D PTS: 2 DIF: Average
5. A 230 000 V-rms powerline carries an average power Pavg = 250 MW a distance of 200 km. If the total
resistance of the cables is 10 ohms, what is the resistive power loss? a. 1.0 MW
b. 2.5 MW c. 5.4 MW d. 12 MW e. 10 kW
ANS: D PTS: 2 DIF: Average
6. Inductive reactance XL is given by a. L
b. L/ c. 1/L d. /L e. 2L
ANS: A PTS: 1 DIF: Easy
7. Capacitive reactance XC is given by a. 1/C
b. C
c. /C d. C/ e. 1/2C
ANS: A PTS: 1 DIF: Easy
8. The total impedance Z of an RLC circuit driven by an ac voltage source at angular frequency is, a.
b. c.
d. e.
ANS: B PTS: 1 DIF: Easy
9. At what frequency will a 12-F capacitor have a reactance XC = 300? a. 44 Hz
b. 88 Hz c. 180 Hz d. 350 Hz e. 280 Hz
10. At what frequency will a 50.0-mH inductor have a reactance XL = 700? a. 352 Hz b. 777 Hz c. 1.25 kHz d. 2.23 kHz e. 14 kHz
ANS: D PTS: 2 DIF: Average
11. A 2.0-F capacitor in series with a 2.0-k resistor is connected to a 60-Hz ac source. Calculate the impedance of the circuit.
a. 1 500 ohms b. 1 800 ohms c. 2 100 ohms d. 2 400 ohms e. 8 600 ohms
ANS: D PTS: 2 DIF: Average
12. A 10.0-F capacitor is plugged into a 110 V-rms 60.0-Hz voltage source, with an ammeter in series. What is the rms value of the current through the capacitor?
a. 0.202 A (rms) b. 0.415 A (rms) c. 0.626 A (rms) d. 0.838 A (rms) e. 0.066 A (rms)
ANS: B PTS: 2 DIF: Average
13. A 0.500-H inductor is connected into a 110 V-rms 60.0-Hz voltage source, with an ammeter in series. What is the rms value of the current through the inductor?
a. 0.189 A (rms) b. 0.292 A (rms) c. 0.584 A (rms) d. 1.19 A (rms) e. 0.093 A (rms)
ANS: C PTS: 2 DIF: Average
14. An LC circuit is to have resonant oscillations at 5.0 MHz. Find the value of a capacitor which will work with a 1.0-mH inductor.
a. 2.0 mF b. 1.0 F c. 0.020 F d. 1.0 pF e. 40 pF
ANS: D PTS: 2 DIF: Average
15. The inductance of a tuning circuit of an AM radio is 4.00 mH. Find the capacitance of the circuit required for reception at 1 200 kHz.
a. 2.10 pF b. 4.40 pF c. 21.2 pF
d. 43.4 pF e. 27.6 pF
ANS: B PTS: 2 DIF: Average
16. Find the resonant frequency for a series RLC circuit where R = 10, C = 5.00 F, and L = 2.00 mH. a. 998 Hz
b. 1.59 kHz c. 2.45 kHz d. 11.3 kHz e. 2.53 kHz
ANS: B PTS: 2 DIF: Average
17. The voltage 8.00 sin (400t) is applied to a series RLC circuit, with R = 200 , L = 0.100 H, and C = 1.00 F. What are the impedance Z and the phase angle ?
a. 200 , 37.0 b. 566 , +87.0 c. 2 470 , 85.4 d. 2 540 , 88.8 e. 393 , 63.0
ANS: C PTS: 3 DIF: Challenging
18. If an R = 1.0-k resistor, a C = 1.0-F capacitor, and an L = 0.20-H inductor are connected in series with a V = 150 sin (377t) volts source, what is the maximum current delivered by the source? a. 0.007 0 A
b. 27 mA c. 54 mA d. 0.31 A e. 0.34 A
ANS: C PTS: 2 DIF: Average
19. If the input to an RLC series circuit is V = Vm cos t, then the current in the circuit is
a. cos t b. c. d. e.
ANS: D PTS: 1 DIF: Easy
20. An RLC series circuit has R = 100 ohms, C = 25 F, and L = 0.16 H. For what angular frequency of an ac voltage is the current flow maximum?
b. 500 rad/s c. 757 rad/s d. 884 rad/s e. 79.6 rad/s
ANS: B PTS: 2 DIF: Average
21. Determine the rms voltage for the circuit.
a. 99 V (rms) b. 140 V (rms) c. 196 V (rms) d. 70 V (rms) e. 110 V (rms)
ANS: A PTS: 1 DIF: Easy
22. Determine the impedance for the circuit.
a. 600 b. 1 200 c. 1 800 d. 2 300 e. 1 100
ANS: C PTS: 2 DIF: Average
a. 55 mA b. 77 mA c. 99 mA d. 0.19 A e. 61 mA
ANS: A PTS: 2 DIF: Average
24. Determine the resonant frequency of the circuit.
a. 159 Hz b. 32 Hz c. 5 Hz d. 500 Hz e. 79.5 Hz
ANS: A PTS: 2 DIF: Average
25. Determine the rms voltage drop across the resistor in the circuit.
a. 55 V b. 77 V c. 9.9 V d. 5.5 V
e. 61 V
ANS: A PTS: 2 DIF: Average
26. Determine the rms voltage drop across the inductor in the circuit.
a. 11 V b. 27.5 V c. 33 V d. 38.5 V e. 30.5 V
ANS: B PTS: 2 DIF: Average
27. Determine the rms voltage drop across the capacitor in the circuit.
a. 55 V b. 77 V c. 110 V d. 154 V e. 198 V
ANS: C PTS: 2 DIF: Average
28. A current I = 3 sin (400 t) amperes flows in a series RL circuit in which L = 1 mH and R = 100. What is the average power loss?
a. 225 W b. 450 W c. 980 W d. 1.12 kW e. 900 W
29. What is the average power dissipation in a series RC circuit if R = 5.00 k, C = 2.00 F, and V = 170 cos (300t)? a. 0.930 W b. 2.60 W c. 28.2 W d. 157 W e. 5.20 W
ANS: B PTS: 2 DIF: Average
30. What is the average power dissipation in an RLC series circuit with R = 10, L = 0.1 H, C = 10 F when driven at resonance by a 100 V-rms source?
a. 100 W b. 500 W c. 1000 W d. 2 kW e. 700 W
ANS: C PTS: 2 DIF: Average
31. A series RLC circuit has an impedance of 120 and a resistance of 64. What average power is delivered to this circuit when Vrms = 90 volts?
a. 36 W b. 100 W c. 192 W d. 360 W e. 12 W
ANS: A PTS: 2 DIF: Average
32. A transformer is to be designed to increase the 30 kV-rms output of a generator to the transmission- line voltage of 345 kV-rms. If the primary winding has 80 turns, how many turns must the secondary have? a. 6 b. 70 c. 920 d. 9 200 e. 12
ANS: C PTS: 2 DIF: Average
33. The primary winding of an electric train transformer has 400 turns and the secondary has 50. If the input voltage is 120V(rms) what is the output voltage?
a. 15 V (rms) b. 30 V (rms) c. 60 V (rms) d. 2.4 V (rms) e. 960 V (rms)
ANS: A PTS: 2 DIF: Average
34. A step-up transformer has an input voltage of 110 V (rms). There are 100 turns on the primary and 1 500 on the secondary. What is the output voltage?
a. 1 600 V (max) b. 1 650 V (rms)
c. 3 260 V (max) d. 165 kV (rms) e. 7.3 V (rms)
ANS: B PTS: 2 DIF: Average
35. A primary current of 6.0 A exists in an ideal iron-core transformer at a primary voltage of 100 volts. If the current in the secondary is 0.75 A, calculate the output voltage.
a. 12.5 V b. 40 V c. 400 V d. 800 V e. 200 V
ANS: D PTS: 2 DIF: Average
36. An ideal step-down transformer has 200 primary turns and 50 secondary turns. If 440 volts (rms) is placed across the primary, what is the current in the secondary when the load resistance is 7.00 ohms? a. 3.6 A (rms)
b. 7.3 A (rms) c. 11.4 A (rms) d. 15.7 A (rms) e. 12.4 A (rms)
ANS: D PTS: 2 DIF: Average
37. Calculate Vout/Vin for the circuit if R = 2.0 k, C = 0.020 F and V = 140V sin(50 000t).
a. 0.02 b. 0.45 c. 0.80 d. 0.98 e. 2.2
ANS: B PTS: 2 DIF: Average
38. The impedance of the parallel RLC circuit shown is given by
a. b.
c. d.
e.
ANS: B PTS: 3 DIF: Challenging
39. The phase angle between V and I is
a.
b.
c.
d.
e.
ANS: A PTS: 3 DIF: Challenging
40. For driving voltage V = Vm sin t, the current through the resistor is
a. Vm sin (t + ) b. Vm cos (t + ) c. sin (t + ) d. sin (t + ) e. sin t
41. An alternating current circuit has resistance R, inductance L and capacitance C in series with a voltage source. Which statement is correct?
a. The voltage across the capacitor leads the voltage across the inductor by 90. b. The voltage across the inductor leads the voltage across the capacitor by 90. c. The voltage across the inductor leads the voltage across the resistor by 180.
d. The voltage across the inductor is out of phase with the voltage across the capacitor by 180.
e. Both voltages lead the voltage across the resistor by 90.
ANS: D PTS: 1 DIF: Easy
42. The power output, Pout, of an ideal step-up transformer that receives power input, Pin, and which has N1
turns in the primary and N2 turns in the secondary coil is given by
a. Pout = Pin. b. Pout = Pin. c. Pout = Pin. d. Pout = Pin. e. Pout = Pin.
ANS: A PTS: 1 DIF: Easy
43. In a typical transmission line, the current I is very small and the voltage V is very large. A unit length of line has resistance R. For a power line that supplies power to 10 000 households, we can conclude that a. IV = I2R. b. I = V/R. c. IV < I2R. d. IV > I2R. e. I2R = 0.
ANS: D PTS: 2 DIF: Average
44. Whenever the alternating current frequency in a series RLC circuit is halved, a. the inductive reactance is doubled and the capacitive reactance is halved. b. the inductive reactance is doubled and the capacitive reactance is doubled. c. the inductive reactance is halved and the capacitive reactance is halved. d. the inductive reactance is halved and the capacitive reactance is doubled. e. the reactance of the circuit remains the same.
ANS: D PTS: 1 DIF: Easy
45. The average power input to a series alternating current circuit is minimum when a. there are only a resistor and capacitor in the circuit.
b. there are only a resistor and inductor in the circuit. c. there is only a resistor in the circuit.
d. XL = XC and the circuit contains a resistor, an inductor and a capacitor. e. there is only a capacitor in the circuit.
ANS: E PTS: 1 DIF: Easy
46. All three circuits shown below have R = 100 , L = 0.1 H and emf = (5.0 V) sin (377 t). Which statement regarding the angular resonance frequencies A, B and C is correct?
a. C > A = B
b. C < A = B
c. A = B = C
d. B < A = C
e. B > A = C
ANS: C PTS: 1 DIF: Easy
47. All three circuits below have R = 100 , C = 1.0 mF and emf = (5.0 V) sin (377 t). The inductors in (B) and (C) are placed sufficiently far apart so that they do not alter one another's inductance. Such inductors add combine like resistors. Which statement regarding the angular resonance frequencies A,
B and C is correct? a. C > A = B b. C < A = B c. A = B = C d. B < A = C e. B > A = C
ANS: C PTS: 2 DIF: Average
48. A 60.0-Hz ac generator with a peak voltage of 110 V drives a series RC circuit with R = 10.0 and C = 300 F. The peak current in the circuit is
a. 8.24 A. b. 8.84 A. c. 11.0 A. d. 12.4 A. e. 23.5 A.
ANS: A PTS: 2 DIF: Average
49. A 60.0-Hz ac generator with a peak voltage of 110 V drives a series RC circuit with R = 10.0 and C = 300 F. The impedance is a. 4.68 . b. 8.84 . c. 10.0 . d. 13.4 . e. 18.8 .
ANS: D PTS: 2 DIF: Average
50. A 60.0-Hz ac generator with a peak voltage of 110 V drives a series RC circuit with R = 10.0 and C = 300 F. The power factor, cos , is
a. 1.00. b. 0.749. c. +0.749. d. +0.834. e. +1.00.
ANS: C PTS: 2 DIF: Average
51. A 60.0-Hz ac generator with a peak voltage of 110 V drives a series RL circuit with R = 10.0 and L = 10.0 mH. The peak current in the circuit is
a. 0.963 A. b. 10.3 A. c. 11.0 A. d. 11.9 A. e. 29.2 A.
ANS: B PTS: 2 DIF: Average
52. A 60.0-Hz ac generator with a peak voltage of 110 V drives a series RL circuit with R = 10.0 and L = 10.0 mH. The impedance is a. 3.77 . b. 9.26 . c. 10.0 . d. 10.7 . e. 13.8 .
ANS: D PTS: 2 DIF: Average
53. A 60.0-Hz ac generator with a peak voltage of 110 V drives a series RL circuit with R = 10.0 and L = 10.0 mH. The power factor, cos , is
a. 1.00. b. 0.936. c. +0.943. d. +0.936. e. +1.00.
54. A 10-F capacitor in an LC circuit made entirely of superconducting materials (R = 0 ) is charged to 100 C. Then a superconducting switch is closed. At t = 0 s, plate 1 is positively charged and plate 2 is negatively charged. At a later time, Vab = +10 V. At that time, Vdc is
a. 0 V. b. 3.54 V. c. 5.0 V. d. 7.07 V. e. 10 V.
ANS: E PTS: 2 DIF: Average
55. The graphs below show a voltage phasor at different instances of time. The voltage phasor which shows the instantaneous value of the voltage with the largest magnitude is
a.
b.
c.
d.
e.
ANS: A PTS: 1 DIF: Easy
56. The graphs below represent current and voltage phasors at one instant of time. The solid arrows represent the voltage phasors, V, and the dashed arrows represent the current phasors, Imax.The graph
which shows the correct relationship between current and voltage phasors for an inductor in an RL circuit is
a.
b.
c.
d.
e.
ANS: A PTS: 1 DIF: Easy
57. The graphs below represent current and voltage phasors at one instant of time. The solid arrows represent the voltage phasors, Vmax, and the dashed arrows represent the current phasors, Imax. The
graph which shows the correct relationship between current and voltage phasors for a capacitor in an
RC circuit is a. b. c. d. e.
ANS: C PTS: 1 DIF: Easy
58. The graphs below show the phasors Vmax and Imax for five RLC series circuits. The solid arrows
represent the voltage phasors, V, and the dashed arrows represent the current phasors, Imax. The graph
which represents a circuit where the inductive reactance is greater than the capacitive reactance is a.
b.
c.
d.
e.
ANS: B PTS: 1 DIF: Easy
59. The graphs below show the phasors Vmax and Imax for five RLC series circuits. The solid arrows
represent the voltage phasors, V, and the dashed arrows represent the current phasors, Imax. The graph
which represents a circuit where the capacitive reactance is greater than the inductive reactance is a.
b.
c.
e.
ANS: A PTS: 1 DIF: Easy
60. In a parallel RLC circuit, where IR = IR, max sin(t), the current through the capacitor, IC, is a. IC = IC, max sin(t).
b. IC = IC, max sin(t).
c. IC = IC, max cos(t).
d. IC = IC, max cos(t).
e. IC = IC, max tan(t).
ANS: D PTS: 1 DIF: Easy
61. In a parallel RLC circuit, where IR = IR, max sin(t), the current through the inductor, IL, is a. IL = IL, max sin(t).
b. IL = IL, max sin(t).
c. IL = IL, max cos(t).
d. IL = IL, max cos(t).
e. IL = IL, max tan(t).
ANS: C PTS: 1 DIF: Easy
62. Which of the following is true about a diode?
a. A diode causes the voltage to shift in phase by 90, i.e., a right angle.
b. A diode has high resistance in one current direction and low resistance in the opposite current direction.
c. A diode can only be used with a transformer. d. All filter circuits contain a diode.
e. All of the above.
ANS: B PTS: 1 DIF: Easy
PROBLEM
63. Suppose the circuit parameters in a series RLC circuit are: L = 1.00 H, C = 10.0 nF, R = 100, and the source voltage is 220 V. Determine the resonant frequency of the circuit and the amplitude of the current at resonance.
ANS:
1.59 MHz, 2.20 A
PTS: 2 DIF: Average
64. A 10.0- resistor, 10.0-mH inductor, and 10.0-F capacitor are connected in series with a 10.0-kHz voltage source. The rms current through the circuit is 0.200 A. Find the rms voltage drop across each of the 3 elements.
ANS: