Test: Part 2
DO NOT REFER TO THE TEXT WHEN TAKING THIS TEST. A GOOD SCORE IS AT LEAST 37 CORRECT. Answers are in the back of the book. It’s best to have a friend check your score the first time, so you won’t memorize the answers if you want to take the test again.
1. If two pure sine waves of the same frequency are 135° out of phase, it’s equivalent to
(a) 
of a cycle.
(b) 
of a cycle.
(c) 
of a cycle.
(d) ⅜ of a cycle.
(e) ¾ of a cycle.
2. What should we do with the individual resistance values in a series RLC circuit if we want to determine the net resistance?
(a) Add them all up.
(b) Multiply them by each other.
(c) Convert them to conductances, add those values to each other, and then convert the result back to resistance.
(d) Convert them to susceptances, multiply them by each other, and then convert the result back to resistance.
(e) Multiply them by each other and then take the square root of the result.
3. When two identical capacitors are connected in series and no mutual capacitance exists, the net capacitance is
(a) ¼ of the value of either individual capacitor.
(b) half the value of either individual capacitor.
(c) the same as the value of either individual capacitor.
(d) twice the value of either individual capacitor.
(e) four times the value of either individual capacitor.
4. At any particular frequency, a capacitor with a negative temperature coefficient
(a) gets less reliable as the temperature rises.
(b) gets more reliable as the temperature rises.
(c) heats up more as its reactance gets farther from zero (increases negatively).
(d) has reactance that gets farther from zero (increases negatively) as the temperature rises.
(e) has reactance that gets closer to zero (decreases negatively) as the temperature rises.
5. Refer to Fig. Test 2-1. What’s the phase relationship between the two pure sine waves A and B?
Test 2-1 Illustration for Part 2 Test Questions 5 and 6.
(a) Wave A lags wave B by 90°.
(b) Wave A lags wave B by 45°.
(c) Wave A lags wave B by 30°.
(d) Waves A and B coincide in phase.
(e) Waves A and B oppose in phase.
6. Refer to Fig. Test 2-1 again. What can we say about the period of wave A with respect to the period of wave B?
(a) The period of wave A equals the period of wave B.
(b) The period of wave A equals half the period of wave B.
(c) The period of wave A equals one and a half times the period of wave B.
(d) The period of wave A equals twice the period of wave B.
(e) Nothing, because we can’t define the relative period.
7. If we connect a 12.6-V automotive battery directly to a 100-ohm resistor, then that resistor dissipates 1.59 W of
(a) conductive power.
(b) apparent power.
(c) true power.
(d) resistive power.
(e) imaginary power.
8. How long does it take for 36.00° of a cycle to pass in a 60.00-Hz sine wave?
(a) 0.01667 ms
(b) 0.1667 ms
(c) 1.667 ms
(d) 16.67 ms
(e) 166.7 ms
9. What’s the period of an AC wave whose frequency is 1.00 kHz?
(a) 1.00 ms
(b) 1.25 ms
(c) 2.50 ms
(d) 5.00 ms
(e) 25.0 ms
10. Consider a series circuit comprising a pure resistance of 60 ohms and an inductive reactance of 100 ohms. What’s the circuit’s complex-number impedance?
(a) 60 − j100
(b) −100 − j60
(c) 60 + j100
(d) −100 + j60
(e) 160 ohms
11. Which of the following capacitor types would most likely have a value of 0.01 μF?
(a) Ceramic
(b) Air variable
(c) Photovoltaic
(d) Electrolytic
(e) Electrodynamic
12. If we connect five 100-pF capacitors in parallel, the net capacitance is
(a) 20 pF.
(b) 50 pF.
(c) 100 pF.
(d) 500 pF.
(e) We need more information to answer this question.
13. If we connect four capacitors as shown in Fig. Test 2-2, the net capacitance C (rounded to two significant figures) is
Test 2-2 Illustration for Part 2 Test Question 13.
(a) 33 pF.
(b) 38 pF.
(d) 67 pF.
(e) 88 pF.
14. When we want an antenna system to work at its best, which of the following properties should we make sure that it has?
(a) The characteristic impedance of the feed line should equal the resistive part of the antenna impedance, and the antenna itself should have no reactance.
(b) The characteristic impedance of the feed line should equal the reactive part of the antenna impedance, and the antenna itself should be a pure reactance.
(c) The characteristic impedance of the feed line should equal the sum of the resistive and reactive parts of the antenna impedance.
(d) The standing-wave ratio (SWR) on the feed line should be zero.
(e) The SWR on the feed line should be extremely high (ideally, infinite).
15. If a pure sine wave has a positive peak voltage of +170 V pk+ and a negative peak voltage of −170 V pk−, then its peak-to-peak voltage is
(a) zero.
(b) 240 V pk-pk.
(c) 340 V pk-pk.
(d) 120 V pk-pk.
(e) a value that requires more information to calculate.
16. If a pure sine wave has a positive peak voltage of +170 V pk+ and a negative peak voltage of −170 V pk−, then its effective or RMS voltage is
(a) zero.
(b) 240 V RMS.
(c) 340 V RMS.
(d) 120 V RMS.
(e) a value that requires more information to calculate.
17. If a pure sine wave has a positive peak voltage of +170 V pk+ and a negative peak voltage of −170 V pk−, then its average voltage is
(a) zero.
(b) 240 V.
(c) 340 V.
(d) 120 V.
(e) a value that requires more information to calculate.
18. We connect two components in series. One has a complex impedance of 10 + j20, the other 40 − j20. What’s the net complex-number impedance of the combination?
(a) 50 + j40
(b) 50 − j40
(c) 50 + j0
(d) 30 + j40
(e) 30 − j40
19. The situation described in Question 18 represents an example of
(a) reactance.
(b) quadrature.
(c) dissipation.
(d) dissonance.
(e) resonance.
20. We run a small electric generator with a moderate load. Then we disconnect that load to let the generator “run free.” What happens?
(a) The generator motor speeds up.
(b) The generator motor slows down.
(c) The output voltage decreases.
(d) It takes more mechanical power to turn the generator’s motor shaft.
(e) The output current increases.
21. Consider a series RLC circuit, where R represents the resistance and X represents the net reactance. We can find the absolute-value impedance according to one of the following formulas. Which one?
(a) Z = R + X
(b) Z = (R2 + X2)1/2
(c) Z = [RX/(R2 + X2)]1/2
(d) Z = 1/(R2 + X2)
(e) Z = R2X2/(R + X)
22. The resistance is less than the reactance in an RL circuit, but neither value is zero or “infinity.” What’s the phase angle?
(a) 0°
(b) Something between 0° and 45°
(c) 45°
(d) Something between 45° and 90°
(e) 90°
23. The resistance equals the reactance in an RL circuit; both values are finite and nonzero. What’s the phase angle?
(a) 0°
(b) Something between 0° and 45°
(c) 45°
(d) Something between 45° and 90°
(e) 90°
24. The resistance is greater than the reactance in an RL circuit, but neither value is zero or “infinity.” What’s the phase angle?
(a) 0°
(b) Something between 0° and 45°
(c) 45°
(d) Something between 45° and 90°
(e) 90°
25. In a series-resonant RLC circuit, which (if any) of the following formulas always holds true? (Remember that L and C stand for actual inductance and capacitance values, not reactance values.)
(a) R = 0
(b) L = C
(c) L = 0
(d) C = 0
(e) None of the above
26. A perfectly conducting (loss-free) AC transmission line carries 200 mA RMS and 100 V RMS. The load contains no reactance, but its resistance equals the characteristic impedance of the line. How much reactive power does the load dissipate?
(a) None
(b) 7.07 W
(c) 14.1 W
(d) 20.0 W
(e) 28.3 W
27. We connect a 400-pF capacitor in parallel with a 20-μH inductor. Then we increase the capacitance to 800 pF and decrease the inductance to 10 μH. What happens to the resonant frequency of the circuit?
(a) It stays the same.
(b) It increases by a factor of 2π.
(c) It increases by a factor of 4π2.
(d) It decreases by a factor of 2π.
(e) It decreases by a factor of 4π2.
28. We connect a 400-pF capacitor in series with a 20-μH inductor. Then we increase the capacitance to 800 pF and decrease the inductance to 10 μH. What happens to the resonant frequency of the circuit?
(a) It stays the same.
(b) It increases by a factor of 2π.
(c) It increases by a factor of 4π2.
(d) It decreases by a factor of 2π.
(e) It decreases by a factor of 4π2.
29. In Fig. Test 2-3, vector A represents
Test 2-3 Illustration for Part 2 Test Questions 29 through 33.
(a) pure inductance.
(b) pure resistance.
(c) pure capacitance.
(d) a combination of resistance and inductance.
(e) a combination of resistance and capacitance.
30. In Fig. Test 2-3, vector B represents
(a) pure inductance.
(b) pure resistance.
(c) pure capacitance.
(d) a combination of resistance and inductance.
(e) a combination of resistance and capacitance.
31. In Fig. Test 2-3, vector C represents
(a) pure inductance.
(b) pure resistance.
(c) pure capacitance.
(d) a combination of resistance and inductance.
(e) a combination of resistance and capacitance.
32. In Fig. Test 2-3, vector D represents
(a) pure inductance.
(b) pure resistance.
(d) a combination of resistance and inductance.
(e) a combination of resistance and capacitance.
33. In Fig. Test 2-3, vector E represents
(a) pure inductance.
(b) pure resistance.
(c) pure capacitance.
(d) a combination of resistance and inductance.
(e) a combination of resistance and capacitance.
34. An air-core coil
(a) works well as a 60-Hz AC transformer.
(b) has less inductance than a toroid-core coil with the same number of turns.
(c) provides high inductance with relatively few turns.
(d) works best at very-low frequencies (VLF) and low frequencies (LF).
(e) makes an efficient loop antenna for VLF and LF transmitting.
35. What’s the net inductance of three 60-mH toroid-core inductors connected in parallel? (Remember that mutual inductance is not a factor with toroidal coils because all the magnetic flux is confined to the core.)
(a) It’s impossible to calculate without more information.
(b) 20 mH
(c) 60 mH
(d) 120 mH
(e) 180 mH
36. What’s the net capacitance of three 60-pF ceramic capacitors connected in parallel? (Assume that no mutual capacitance exists.)
(a) It’s impossible to calculate without more information.
(b) 20 pF
(c) 60 pF
(d) 120 pF
(e) 180 pF
37. A step-up RF transformer has a turns ratio of 1:10. We connect a purely resistive load of 10k to the secondary winding. If we connect a radio transmitter to the primary winding, what purely resistive impedance will that transmitter “see”?
(a) 0.10 ohm
(b) 1.0 ohms
(c) 10 ohms
(d) 0.10k
(e) 1.0k
38. Consider again the transformer described in Question 37. If the transmitter is designed to operate into a purely resistive impedance of 50 ohms (as most ham radios are, for example), what purely resistive impedance should we connect to the secondary to get optimum performance from the transmitter, which remains connected to the primary?
(a) 5.0k
(b) 0.50k
(c) 50 ohms
(d) 5.0 ohms
(e) 0.50 ohms
39. When we translate 100 nH into microhenrys, we get
(a) 0.001 μH.
(b) 0.010 μH.
(c) 0.100 μH.
(d) 1.00 μH.
(e) 10.0 μH.
40. We can denote a specific pure inductive reactance on the RXL half-plane as a point
(a) on the positive real-number axis.
(b) on the positive imaginary-number axis.
(c) in the lower-right part of the half-plane, but not on either axis.
(d) in the upper-right part of the half-plane, but not on either axis.
(e) on the negative imaginary-number axis.
41. How many degrees of phase indicate the time-point in a cycle at which a pure sine wave, with no DC component, has a negative-going voltage of zero? (A cycle begins when the voltage is zero and positive-going.)
(a) 0°
(b) 45°
(c) 90°
(d) 180°
(e) 270°
42. How many degrees of phase indicate the time-point in a cycle at which a pure sine wave, with no DC component, reaches its maximum negative instantaneous voltage?
(a) 0°
(b) 45°
(c) 90°
(d) 180°
(e) 270°
43. You want to use a quarter-wave transmission-line section to match a feed line with a characteristic impedance of 50 ohms to an antenna with a purely resistive impedance of 113 ohms. What characteristic impedance should that matching section have?
(a) 63 ohms
(b) 69 ohms
(c) 75 ohms
(d) 82 ohms
(e) 91 ohms
44. What waveform does AC with a lot of harmonic energy have?
(a) Sine
(b) Triangular
(c) Ramp
(d) Square
(e) We need more information to say.
45. In a resonant RLC circuit, the complex-number reactance values are both nonzero, but when you add them, you get
(a) j0.
(b) a positive imaginary number.
(c) a negative imaginary number.
(d) a positive real number.
(e) a negative real number.
46. In an RLC circuit comprising a discrete resistor, inductor, and capacitor, resonance occurs at
(a) a specific frequency and all its even-numbered harmonics.
(b) a specific frequency and all its odd-numbered harmonics.
(c) a specific frequency and all its harmonics.
(d) a single specific frequency.
(e) None of the above
47. Which of the following factors (a), (b), (c), or (d), if any, does not affect the characteristic impedance of coaxial cable?
(a) The outside diameter of the center conductor
(b) The inside diameter of the shield
(c) The spacing between the center conductor and shield
(d) The nature of the insulating material (dielectric) between the center conductor and shield
(e) Any or all of the above factors can affect the characteristic impedance of coaxial cable.
48. In a series RL circuit in which R = 910 ohms and XL = 910 ohms, the current lags the voltage by
(a) 90°.
(b) 60°.
(c) 45°.
(d) 30°.
(e) 0°.
49. Two pure sine-wave signals both lack DC components, have the same frequency, and have the same peak-to-peak voltage; yet when we combine them we get no signal whatsoever. What’s the phase difference between these two sine waves?
(a) 0°
(b) 180°
(c) 360°
(d) Any whole-number multiple of 180°
(e) We need more information to say.
50. A series RC circuit has a resistance of 10k and a capacitive reactance of −j13 ohms at a particular frequency. The current leads the voltage by
(a) 90°.
(b) 60°.
(c) 45°.
(d) 30°.
(e) None of the above