20 Questions
| Attempts: 643

Questions and Answers

- 1.The power in a pure reactance is
- A.
Radiated

- B.
True

- C.
Imaginary

- D.
Apparent

- 2.Which of the following is not an example of true power?
- A.
Power in the form of heat, produced by dc flowing through a resistor

- B.
Power in the form of electromagnetic fields, radiated from a radio antenna

- C.
The product of the rms ac through a capacitor and the rms voltage across it

- D.
Power in the form of heat, produced by losses in an RF transmission line

- 3.Suppose the apparent power in a circuit is 100 W, and the imaginary power is 40 W. What isthe true power?
- A.
92 W

- B.
100 W

- C.
140 W

- D.
It is impossible to determine from this information

- 4.Power factor is equal to
- A.
Apparent power divided by true power

- B.
Imaginary power divided by apparent power

- C.
Imaginary power divided by true power

- D.
True power divided by apparent power

- 5.Suppose a circuit has a resistance of 300 Ω and an inductance of 13.5 µH in series, and isoperated at 10.0 MHz. What is the power factor?
- A.
0.334

- B.
0.999

- C.
0.595

- D.
It cannot be determined from the information given.

- 6.Suppose a series circuit has Z = 88.4 Ω, with R = 50.0 Ω. What is the power factor, expressed as a percentage?
- A.
99.9 percent

- B.
56.6 percent

- C.
60.5 percent

- D.
29.5 percent

- 7.Suppose a series circuit has R = 53.5 Ω, with X = 75.5 Ω. What is the power factor, expressed as a percentage?
- A.
70.9 percent

- B.
81.6 percent

- C.
57.8 percent

- D.
63.2 percent

- 8.The phase angle in an ac circuit is equal to
- A.
Arctan (Z/R)

- B.
Arctan (R/Z)

- C.
Arctan (R/X)

- D.
Arctan (X/R)

- 9.Suppose an ac ammeter and an ac voltmeter indicate that there are 220 W of VA power in acircuit that consists of a resistance of 50 Ω in series with a capacitive reactance of −20 Ω. What is the true power?
- A.
237 W

- B.
204 W

- C.
88.0 W

- D.
81.6 W

- 10.Suppose an ac ammeter and an ac voltmeter indicate that there are 57 W of VA power in acircuit. The resistance is known to be 50 Ω, and the true power is known to be 40 W. What is the absolute-value impedance?
- A.
50 Ω

- B.
57 Ω

- C.
71 Ω

- D.
It is impossible to determine on the basis of this data.

- 11.Which of the following should be minimized in an RF transmission line?
- A.
The load impedance

- B.
The load resistance

- C.
The line loss

- D.
The transmitter power

- 12.Which of the following does not increase the loss in a transmission line?
- A.
Reducing the power output of the source

- B.
Increasing the degree of mismatch between the line and the load

- C.
Reducing the diameter of the line conductors

- D.
Raising the frequency

- 13.Which of the following is a significant problem that standing waves can cause in an RFtransmission line?
- A.
Line overheating

- B.
Excessive power loss

- C.
Inaccuracy in power measurement

- D.
All of the above

- 14.Suppose a coil and capacitor are in series. The inductance is 88 mH and the capacitance is1000 pF. What is the resonant frequency?
- A.
17 kHz

- B.
540 Hz

- C.
17 MHz

- D.
540 kHz

- 15.Suppose a coil and capacitor are in parallel, with L = 10.0 µH and C = 10 pF. What is fo?
- A.
15.9 kHz

- B.
5.04 MHz

- C.
15.9 MHz

- D.
50.4 MHz

- 16.Suppose you want to build a series-resonant circuit with fo = 14.1 MHz. A coil of 13.5 µH isavailable. How much capacitance is needed?
- A.
0.945 µF

- B.
9.45 pF

- C.
94.5 pF

- D.
945 pF

- 17.Suppose you want to build a parallel-resonant circuit with fo = 21.3 MHz. A capacitor of22.0 pF is available. How much inductance is needed?
- A.
2.54 mH

- B.
254 µH

- C.
25.4 µH

- D.
2.54 µH

- 18.A 1⁄4-wave section of transmission line is cut for use at 21.1 MHz. The line has a velocityfactor of 0.800. What is its physical length in meters?
- A.
11.1 m

- B.
3.55 m

- C.
8.87 m

- D.
2.84 m

- 19.What is the fourth harmonic of 800 kHz?
- A.
200 kHz

- B.
400 kHz

- C.
3.20 MHz

- D.
4.00 MHz

- 20.Suppose you want to build a 1⁄2-wave dipole antenna designed to have a fundamentalresonant frequency of 3.60 MHz. How long should you make it, as measured from end to end in feet?
- A.
130 ft

- B.
1680 ft

- C.
39.7 ft

- D.
515 ft

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