Is equal to driving voltage divided by output voltage. TE

D. Is equal to driving voltage divided by output voltage. TE

B. Is equal to output power divided by driving power.

C. Depends on the nature of the load.

E. Is equal to driving current divided by output current.

22. Admittance is:

A. The reciprocal of reactance.

B. The reciprocal of resistance.

C. A measure of the opposition a circuit offers to ac.

D. A measure of the ease with which a circuit passes ac.

E. Another expression for absolute-value impedance.

23. The absolute-value impedance Z of a parallel RLC circuit, where R is the resistance and X is the net reactance, is found according to the formula:

⫽ R + X. A. Z

2 ⫽R B. Z 2 +X 2 .

2 ⫽ RX/(R C. Z 2 +X 2 ).

⫽ 1/(R D. Z 2 +X 2 ). ⫽R E. Z 2 X 2 /(R + X).

24. Complex numbers are used to represent impedance because:

A. Reactance cannot store power.

Test: Part two 351

B. Reactance isn’t a real physical thing.

C. They provide a way to represent what happens in resistance-reactance circuits.

D. Engineers like to work with sophisticated mathematics.

E. No! Complex numbers aren’t used to represent impedance.

25. Which of the following does not affect the capacitance of a capacitor?

A. The mutual surface area of the plates.

B. The dielectric constant of the material between the plates (within reason).

C. The spacing between the plates (within reason).

D. The amount of overlap between plates.

E. The frequency (within reason).

26. The zero-degree phase point in an ac sine wave is usually considered to be the instant at which the amplitude is:

A. Zero and negative-going.

B. At its negative peak.

C. Zero and positive-going.

D. At its positive peak.

E. Any value; it doesn’t matter.

27. The inductance of a coil can be continuously varied by:

A. Varying the frequency.

B. Varying the net core permeability.

C. Varying the current in the coil.

D. Varying the wavelength.

E. Varying the voltage across the coil.

28. Power factor is defined as the ratio of:

A. True power to VA power.

B. True power to imaginary power.

C. Imaginary power to VA power.

D. Imaginary power to true power.

E. VA power to true power.

29. A 50 Ω feed line needs to be matched to an antenna with a purely resistive impedance of 200 Ω. A quarter-wave matching section should have:

o A. Z ⫽ 150 Ω. o B. Z ⫽ 250 Ω. o ⫽ 125 Ω. C. Z o D. Z ⫽ 133 Ω. o E. Z ⫽ 100 Ω.

352 Test: Part two

30. The vector 40 + j30 represents:

A. 40 Ω resistance and 30 µH inductance.

B. 40 uH inductance and 30 Ω resistance.

C. 40 Ω resistance and 30 Ω inductive reactance.

D. 40 Ω inductive reactance and 30 Ω resistance.

E. 40 uH inductive reactance and 30 Ω resistance.

31. In a series RC circuit, where, R ⫽ 300 Ω and X C ⫽ −30 Ω:

A. The current leads the voltage by a few degrees.

B. The current leads the voltage by almost 90 degrees.

C. The voltage leads the current by a few degrees.

D. The voltage leads the current by almost 90 degrees.

E. The voltage leads the current by 90 degrees.

32. In a step-down transformer:

A. The primary voltage is greater than the secondary voltage.

B. The primary impedance is less than the secondary impedance.

C. The secondary voltage is greater than the primary voltage.

D. The output frequency is higher than the input frequency.

E. The output frequency is lower than the input frequency.

33. A capacitor of 470 pF is in parallel with an inductor of 4.44 µH. What is the resonant frequency?

A. 3.49 MHz.

B. 3.49 kHz.

C. 13.0 MHz.

D. 13.0 GHz.

E. Not determinable from the data given.

34. A sine wave contains energy at:

A. Just one frequency.

B. A frequency and its even harmonics.

C. A frequency and its odd harmonics.

D. A frequency and all its harmonics.

E. A frequency and its second harmonic only.

35. Inductive susceptance is:

A. The reciprocal of inductance.

B. Negative imaginary.

C. Equal to capacitive reactance.

D. The reciprocal of capacitive susceptance.

E. A measure of the opposition a coil offers to ac.

Test: part two 353

36. The rate of change (derivative) of a sine wave is itself a wave that:

A. Is in phase with the original wave.

B. Is 180 degrees out of phase with the original wave.

C. Leads the original wave by 45 degrees of phase.

D. Lags the original wave by 90 degrees of phase.

E. Leads the original wave by 90 degrees of phase.

37. True power is equal to:

A. VA power plus imaginary power.

B. Imaginary power minus VA power.

C. Vector difference of VA and reactive power.

D. VA power; the two are the same thing.

E. 0.707 times the VA power.

38. Three capacitors are connected in series. Their values are 47 µF, 68 µF, and 100 µF. The total capacitance is:

A. 215 µF.

B. Between 68 µF and 100 µF.

C. Between 47 µF and 68 µF.

D. 22 µF.

E. Not determinable from the data given.

39. The reactance of a section of transmission line depends on all of the following except:

A. The velocity factor of the line.

B. The length of the section.

C. The current in the line.

D. The frequency.

E. The wavelength.

40. When confronted with a parallel RLC circuit and you need to find the complex impedance:

A. Just add the resistance and reactance to get R + jX.

B. Find the net conductance and susceptance, then convert to resistance and reactance, and add these to get R + jX.

C. Find the net conductance and susceptance, and just add these together to get R + jX.

D. Rearrange the components so they’re in series, and find the complex impedance of that circuit.

E. Subtract reactance from resistance to get R − jX.

41. The illustration in Fig. Test 2-2 shows a vector R + jX representing:

C A. X ⫽ 60 Ω and R ⫽ 25 Ω.

354 Test: Part two

L B. X ⫽ 60 Ω and R ⫽ 25 Ω. L C. X ⫽ 60 µH and R ⫽ 25 Ω.

⫽ 60 µF and R ⫽ 25 Ω. D. C ⫽ 60 µH and R ⫽ 25 Ω. E. L

TEST 2-2 Illustration for PART TWO test question 41.

42. If two sine waves have the same frequency and the same amplitude, but they cancel out, the phase difference is:

A. 45 degrees.

B. 90 degrees.

C. 180 degrees.

D. 270 degrees.

E. 360 degrees.

43. A series circuit has a resistance of 50 Ω and a capacitive reactance of −37 Ω. The phase angle is:

A. 37 degrees.

B. 53 degrees.

C. −37 degrees.

D. −53 degrees.

E. Not determinable from the data given.

44. A 200-Ω resistor is in series with a coil and capacitor; X L ⫽ 200 Ω and X C ⫽ −100 Ω. The complex impedance is:

A. 200 − j100.

Test: Part two 355

B. 200 − j200.

C. 200 + j100.

D. 200 + j200.

E. Not determinable from the data given.

45. The characteristic impedance of a transmission line:

A. Is negative imaginary.

B. Is positive imaginary.

C. Depends on the frequency.

D. Depends on the construction of the line.

E. Depends on the length of the line.

46. The period of a wave is 2 ⫻ 10 −8 second. The frequency is: ⫻ 10 A. 2 8 Hz.

B. 20 MHz.

C. 50 kHz.

D. 50 MHz.

E. 500 MHz.

47. A series circuit has a resistance of 600 Ω and a capacitance of 220 pF. The phase angle is:

A. −20 degrees.

B. 20 degrees.

C. −70 degrees.

D. 70 degrees.

E. Not determinable from the data given.

48. A capacitor with a negative temperature coefficient:

A. Works less well as the temperature increases.

B. Works better as the temperature increases.

C. Heats up as its value is made larger.

D. Cools down as its value is made larger.

E. Has increasing capacitance as temperature goes down.

49. Three coils are connected in parallel. Each has an inductance of 300µH. There is no mutual inductance. The net inductance is:

D. 17.3 µH.

E. 173 µH.

356 Test: Part two

50. An inductor shows 100 Ω of reactance at 30.0 MHz. What is its inductance?

A. 0.531 µH.

B. 18.8 mH.

C. 531 µH.

D. 18.8 µH.

E. It can’t be found from the data given.