ch11

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46. The combined opposition offered by resistance and reactance is called _______________.

impedance

inductors used at higher frequencies are often called

C. RF chokes

28. The electrical property that opposes any change in the magnitude of current in a circuit is called

D. inductance

48. The letter _______________ is the symbol used to represent inductance.

x

44. The voltage leads the current by exactly _______________ degrees in an ideal inductor.

90

22. The high voltage generated when an inductive circuit is opened is known as

A. an inductive kick

18. Shields often used to protect inductors from the influence of magnetic fields are made from

A. magnetic materials

27. The time required for the current through the resistor-inductor to rise to 63.2 percent of its final value is called a

A. time constant

29. When the magnetic flux from one conductor induces a voltage in another electrically isolated conductor, it is called

B. mutual inductance

21. Which of the following is not a rating of an inductor?

B. reactance

23. The opposition of an inductor to alternating current is called

B. reactance

50. Laminated-iron-core inductors are often referred to as filter _______________.

chokes

36. The inductance of a conductor can be greatly _______________ by forming the conductor into a coil.

increased

39. The base unit of _______________ is the henry.

inductance

38. Lenz's law states that a cemf always has a polarity that _______________ the force that created it.

opposes

30. Which law states that a cemf always has a polarity that opposes the force that created it?

B. Lenz's law

25. What is the current and voltage phase relationship in an ideal inductor?

B. voltage leads current by 90

24. What is the reactance of a 3-H inductor when the frequency is 100Hz?

C. 1884 Ω

31. Which of the following determines the inductance of an inductor?

C. diameter of the coil A. type of core material B. spacing between turns of wire

26. The combined opposition offered by resistance and reactance is called

C. impedance

32. Which of the following is not a type of inductor?

C. mica

19. Most large inductors used at power frequencies use

D. laminated iron cores

33. What type of cores do most large inductors use at power frequencies?

D. laminated iron cores

35. Inductance is the electrical property that opposes any change in the magnitude of _______________ in a circuit.

current

49. The quality of an inductor is improved by minimizing the _______________.

dc resistance

10. Chip inductors are available in the mH and H range of inductance.

false

14. Inductors that are used at higher frequencies are often called AF coils.

false

15. The counter emf generated when an inductive circuit is opened is known as inductive resonance.

false

17. The opposition of an inductor to direct current is called reactance.

false

4. Induced emf is always aiding and is sometimes called emf.

false

6. The base unit of inductance is the gilbert.

false

8. One way of classifying inductors is by the type of material used for the coil of the inductor.

false

Inductance is the electrical property that opposes any change in the magnitude of voltage in a circuit.

false

34. All conductors possess _______________.

magnetic fields

40. If all other factors are equal, an iron-core inductor has _______________ inductance than an air-core inductor.

more

37. When the magnetic flux from one conductor induces a voltage in another, electrically isolated conductor, it is called _______________ inductance.

mutual

43. The _______________ of an inductor to alternating current is called reactance.

opposition

45. For an inductor, quality is equal to inductive reactance divided by ______________.

resistance

47. The current concentrating near the surface of a conductor at high frequencies is known as _______________ effect.

skin

41. The adjustable ferrite core material used in a variable inductor is called a(n) _______________.

slug

11. Shields used to protect inductors from the influence of magnetic fields other than their own are made from a magnetic material.

true

12. Inductors used at power frequencies have inductances ranging from about 0.1 to 100 H.

true

13. Laminated iron-core inductors are often referred to as filter chokes.

true

16. The resistance between the terminals of an inductor as measured with an ohmmeter is sometimes called the ohmic resistance.

true

2. Inductors are also known as chokes, reactors, and coils.

true

3. The inductance of a conductor can be greatly increased by forming the conductor into a coil.

true

5. Inductance converts no electric energy into heat energy.

true

7. If all other factors are equal, an air-core inductor has less inductance than an iron-core inductor.

true

9. The adjustable ferrite core inside a variable inductor is called a slug.

true


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