ch11
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