# NAVEDTRA 14174A, NEETS, MODULE 02 ALTERNATING CURRENT AND TRANSFORMERS

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1. The magnetic field surrounding a straight conductor is (a) what shape, and (b) is in what position relative to the conductor? (1 point)

(a) Concentric circles (b) Parallel

(a) Concentric circles (b) Perpendicular

(a) Concentric circles (b) Parallel (your response)
2. Alternating current can be defined as current that varies in

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amplitude and direction
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magnitude and phase

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amplitude and time

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time and phase
amplitude and direction
3. Electrostatic lines of force radiate from a charged particle along what type of lines?

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Elliptical lines

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Orbital lines

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Straight lines
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Curved lines
Straight lines
4. If a coil is wound in layers, its inductance will be greater than that of a similar single-layer coil because of a higher

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permeability

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conductance

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reluctance

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5. What is the unit of measurement for inductance?

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Rel

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Ohm

•

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Henry
henry
6. Inductors experience copper loss for what reason?

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Because all inductors have resistance which dissipates power
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Because the inertia of the magnetic field must be overcome every time the direction of current changes

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Because of flux leakage in the copper core

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Because the reactance of an inductor is greater than the resistance of an inductor
Because all inductors have resistance which dissipates power
7. The power consumed in a conductor in realigning the atoms which set up the magnetic field is known as what type of loss?

Heat loss

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Hysteresis loss
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Field loss

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Magnetic loss
8. The direction of the induced voltage in an inductor may be found by application of which of the following rules?

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The right-hand rule for conductors

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The left-hand rule for inductors

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The left-hand rule for generators

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The right-hand rule for motors
The left-hand rule for generators
9. When the number of turns is increased in a coil from 2 to 4, the total inductance will increase by a factor of

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four
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two

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six

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eight
four
10. Two capacitors are identical with the exception of the material used for the dielectric. Which of the following combinations of dielectric materials will cause the capacitors to have almost the same capacitance?

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Mica, petroleum

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Vacuum, air

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Petroleum, rubber

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Glass, paraffin paper
Vacuum, air
11. Maximum current will flow in an LR circuit after a minimum of how many time constants have elapsed?

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Five
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Three

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One

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Four
five
12. What is the symbol for inductance?

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L
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XL

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H

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IND
L
13. Electrostatic fields have what effect on (a) free electrons, and (b) bound electrons?

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(a) Attracts them to the positive charges (b) Frees them from their orbits

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(a) Attracts them to the negative charges (b) Frees them from their orbits

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(a) Attracts them to the positive charges (b) Distorts their orbits

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(a) Attracts them to the negative charges (b) Distorts their orbits
(a) Attracts them to the negative charges (b) Distorts their orbits
14. When you grasp a coil in your left hand with your thumb pointing in the direction of the north pole, your fingers will be wrapped around the coil in the direction of the

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magnetic field

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voltage potential

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south pole

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current flow
current flow
15. When does mutual inductance occur between inductors?

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Whenever the effect of one inductor is aided by another inductor

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Whenever eddy-currents do not exist

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Whenever the effect of one inductor is opposed by another inductor

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Whenever the flux of one inductor causes an emf to be induced in another inducto
Whenever the effect of one inductor is aided by another inductor
16. The hollow form of nonmagnetic material found in the center of an air core coil has what purpose?

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To act as a low resistance path for flux

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To support the windings

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To serve as a container for the core

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To focus the magnetic flux
To support the windings
17. Mutual inductance between two coils is affected by which of the following factors?

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Material of the windings

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Hysteresis characteristics of the coils

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Direction of the coil windings

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Physical dimensions of the coils
Material of the windings
18. When electrons are moved in a conductor by a magnetic field, a force known by which of the following terms is created?

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Voltage

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Electromotive

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Potential difference

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All of the above
Potential difference
19. The property of inductance offers opposition to which of the following quantities?

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Changes in current
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Constant voltage

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Constant current

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Changes in voltage
Changes in current
20. Which of the following statements accurately describes the magnetic field surrounding a current-carrying conductor?

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It is perpendicular to the conductor and maximum at the most negative point of the conductor

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It is perpendicular to and equal along all parts of the conductor

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It is parallel to and equal along all parts of the conductor

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It is parallel to and maximum at the most negative part of the conductor
It is perpendicular to and equal along all parts of the conductor
21. What physical property is similar to inductance?

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Inertia
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Motion

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Mass

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Velocity
Inertia
22. As the current through a capacitor increases, which of the following types of capacitor losses will increase?

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Plate-leakage

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Plate-breakdown

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Dielectric-hysteresis

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Dielectric-leakage
Dielectric-leakage
23. How are inductors classified?

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By core type
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By conductor type

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By the number of turns

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By the direction of the windings on the core
By core type
24. The coefficient of coupling between two coils is a measure of what factor?

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The distance between the coils

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The relative positive of the coils

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The turns ratio of the coils

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The magnetic flux ratio linking the coils
The magnetic flux ratio linking the coils
25. Rapid reversals in the polarity of the line voltage applied to a capacitor will cause what type of capacitor power loss?

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Dielectric-leakage

•

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Dielectric-hysteresis

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Plate-leakage
Dielectric-hysteresis
26. Power consumed by an iron core inductor in reversing the magnetic field of the core is termed as what type of loss?

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Hysteresis loss
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Heat loss

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Iron loss

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Eddy-current loss
Hysteresis loss
27. How are fixed capacitors classified?

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By the thickness of their conductors

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By their dielectric materials

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By their plate size

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By the thickness of their dielectric materials
By their dielectric materials
28. The value of current of an ac waveform taken at any particular moment of time is what type of value?

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Average value

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Effective value

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Instantaneous value

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Peak-to-peak value
Instantaneous value
29. Which of the following actions will increase the capacitance of a capacitor?

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The plates are moved closer together

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The plates are moved farther apart

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The dielectric constant is decreased

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Both 2 and 3 above
The plates are moved closer together
30. What is the symbol for inductance?

•

•
XL

•
H

•
IND
L
31. What physical property is similar to inductance?

•
Mass

•
Motion

•
Inertia
•
Velocity
Inertia
32. Which of the following factors will NOT affect the value of inductance of a coil?

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Diameter of the coil

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Core materials used

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Number of coil turns

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Conductor tensility
Conductor tensility
33. Which of the following properties surrounds a current-carrying conductor?

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An attractive force

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A repulsive force

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An electrostatic field

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A magnetic field
A magnetic field
34. A waveform is a graphic plot of what quantities?

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Amplitude versus time

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Current versus time

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Magnitude versus amplitude

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Voltage versus amplitude
Amplitude versus time
35. The left-hand rule for generators states that the thumb of the left hand points in the direction of motion of the

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induced current

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conductor
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generator poles

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magnetic field
conductor
36. Which of the following types of capacitors are referred to as self-healing?

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Ceramic

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Mica

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Paper

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Oil
Oil
37. Normally, most coils have cores composed of either air or

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carbon steel

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soft iron

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carbon

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copper
soft iron
38. If the radius of a coil is doubled, its inductance is increased by what factor?

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One

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Two

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Eight

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Four
Four
39. The difference in potential across a resistor, created by current through the resistor is an example of which of the following forces?

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Inertia

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Electromotive
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Resistive

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Inductive
Electromotive
40. A capacitor is a device that stores energy in a/an

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molecular field

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induced field

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electrostatic field
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electromagnetic field
electrostatic field
41. What term applies to the power loss in an iron core inductor due to the current induced in the core?

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Heat loss

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Eddy-current loss

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Hysteresis loss

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Iron loss
Eddy-current loss
42. One L/R time constant is equal to the time required for the current in an inductor to reach what portion of its maximum value?

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25.2%

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63.2%
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12.8%

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37.8%
63.2%
43. Two capacitors are identical with the exception of the material used for the dielectric. Which of the following combinations of dielectric material will cause capacitor (b) to have a larger capacitance than capacitor (a)?

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(a) Glass (b) Paraffin paper

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(a) Glycerine (b) Pure water
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(a) Paraffin paper (b) Petroleum

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(a) Petroleum (b) Air
(a) Glycerine (b) Pure water
44. What is the symbol used to denote the basic unit of measurement for inductance?

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L

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F

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I

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H
H
45. The property of inductance offers opposition to which of the following quantities?

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Changes in current

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Changes in voltage

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Constant current

•
Constant voltage
Changes in current
46. A soft iron core will increase inductance because it has which of the following characteristics?

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Low permeability and high reluctance

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Low permeability and low reluctance

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High permeability and low reluctance

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High permeability and high reluctance
High permeability and low reluctance
47. Alternating current has replaced direct current in modern transmission systems because it has which of the following advantages?

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Ac can be transmitted at lower voltage levels

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Ac can be readily stepped up or down

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Ac can be transmitted with no line loss

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Ac can be transmitted at higher current levels
Ac can be readily stepped up or down
48. If the length of a coil is doubled while the number of turns is kept the same, this will have (a) what effect on inductance and (b) by what factor?

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(a) Increase, (b) by 4 times

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(a) Decrease, (b) by 1/2

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(a) Decrease, (b) by 1/4

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(a) Increase, (b) by 2 times
(a) Decrease, (b) by 1/2
49. Self-induced emf is also known as what force?

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Counter electromotive force

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Inertial force

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magnetic force

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Electromotive force
Counter electromotive force
50. What is the unit of measurement for frequency?

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Hertz

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Period

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Cycle

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Maxwell
Hertz
51. When a magnetic field moves through a stationary conductor, the electrons in orbit are affected in what manner?

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They are dislodged from orbit

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They bunch up on one side of the nucleus

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They move closer to their nucleus

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They move closer to other orbiting electrons
They are dislodged from orbit
52. What is the unit of measurement for inductance?

•
Rel

•

•
Ohm

•
Henry
Henry
53. The maximum voltage that can be applied to a capacitor without causing current flow through the dielectric is called

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breaking voltage

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working voltage
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limiting voltage

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conduction voltage
working voltage
54. Capacitance is defined as the property of a circuit that

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opposes a change in current

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aids a change in voltage

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opposes a change in voltage

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aids a change in current
opposes a change in voltage
55. Before a 120-volt dc source can be used to power a 12-volt load, the voltage must be reduced. Which of the following methods can be used?

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A resistor placed in series with the load
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A step-down transformer placed in parallel-with the load

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A step-down transformer placed in series with load

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A resistor placed in parallel with the load
A resistor placed in series with the load
56. The property of inductance is present in which of the following electrical circuits?

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An ac circuit

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A dc circuit

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A resistive circuit

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Each of the above
Each of the above
57. Which of the following factors determine(s) the intensity of a magnetic field surrounding a coil?

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The amount of current flow through the coil

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The type of core material

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The number of turns in the conductor

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All of the above
All of the above
58. What type of dielectric is LEAST sensitive to power dielectric-hysteresis losses?

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Pure water

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Air

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Mica

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Vacuum
Vacuum
59. Which, if any, of the following conditions may cause a capacitor to suffer power losses?

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Dielectric hysteresis
•

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Plate heating

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None of the above
Dielectric hysteresis
60. Capacitance and inductance in a circuit are similar in which of the following ways?

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Both aid voltage

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Both prevent the storage of energy

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Both oppose current

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Both cause the storage of energy
Both cause the storage of energy

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 Author: david11090 ID: 232171 Filename: NAVEDTRA 14174A, NEETS, MODULE 02 ALTERNATING CURRENT AND TRANSFORMERS Updated: 2013-08-31 19:55:49 Tags: transformers Folders: Description: quiz one of one Show Answers:

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