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

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




(a) Linked oblong (b) Parallel


(a) Concentric circles (b) Parallel


(a) Concentric circles (b) Perpendicular


(a) Linked oblong (b) Perpendicular

Alternating current can be defined as current that varies in



• 
amplitude and direction
• 
magnitude and phase

• 
amplitude and time

• 
time and phase

Electrostatic lines of force radiate from a charged particle along what type of lines?



• 
Elliptical lines

• 
Orbital lines

• 
Straight lines
• 
Curved lines

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



• 
permeability

• 
conductance

• 
reluctance

• 
flux linkage

What is the unit of measurement for inductance?



• 
Rel

• 
Ohm

• 
Farad

• 
Henry

Inductors experience copper loss for what reason?



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

• 
Because of flux leakage in the copper core

• 
Because the reactance of an inductor is greater than the resistance of an inductor

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

• 
Hysteresis loss
• 
Field loss

• 
Magnetic loss

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



• 
The right-hand rule for conductors

• 
The left-hand rule for inductors

• 
The left-hand rule for generators

• 
The right-hand rule for motors

When the number of turns is increased in a coil from 2 to 4, the total inductance will increase by a factor of



• 
four
• 
two

• 
six

• 
eight

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?



• 
Mica, petroleum

• 
Vacuum, air

• 
Petroleum, rubber

• 
Glass, paraffin paper

Maximum current will flow in an LR circuit after a minimum of how many time constants have elapsed?



• 
Five
• 
Three

• 
One

• 
Four

What is the symbol for inductance?



• 
L
• 
XL

• 
H

• 
IND

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



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

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

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

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

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



• 
magnetic field

• 
voltage potential

• 
south pole

• 
current flow

When does mutual inductance occur between inductors?



• 
Whenever the effect of one inductor is aided by another inductor 

• 
Whenever eddy-currents do not exist

• 
Whenever the effect of one inductor is opposed by another inductor

• 
Whenever the flux of one inductor causes an emf to be induced in another inducto

The hollow form of nonmagnetic material found in the center of an air core coil has what purpose?



• 
To act as a low resistance path for flux

• 
To support the windings

• 
To serve as a container for the core

• 
To focus the magnetic flux

Mutual inductance between two coils is affected by which of the following factors?



• 
Material of the windings

• 
Hysteresis characteristics of the coils

• 
Direction of the coil windings

• 
Physical dimensions of the coils

When electrons are moved in a conductor by a magnetic field, a force known by which of the following terms is created?



• 
Voltage

• 
Electromotive

• 
Potential difference 

• 
All of the above

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



• 
Changes in current
• 
Constant voltage

• 
Constant current

• 
Changes in voltage

Which of the following statements accurately describes the magnetic field surrounding a current-carrying conductor?



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

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

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

• 
It is parallel to and maximum at the most negative part of the conductor

What physical property is similar to inductance?



• 
Inertia
• 
Motion

• 
Mass

• 
Velocity

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



• 
Plate-leakage

• 
Plate-breakdown

• 
Dielectric-hysteresis

• 
Dielectric-leakage

How are inductors classified?



• 
By core type
• 
By conductor type

• 
By the number of turns

• 
By the direction of the windings on the core

The coefficient of coupling between two coils is a measure of what factor?



• 
The distance between the coils

• 
The relative positive of the coils

• 
The turns ratio of the coils

• 
The magnetic flux ratio linking the coils

Rapid reversals in the polarity of the line voltage applied to a capacitor will cause what type of capacitor power loss?



• 
Dielectric-leakage

• 
Plate-loading

• 
Dielectric-hysteresis 

• 
Plate-leakage

Power consumed by an iron core inductor in reversing the magnetic field of the core is termed as what type of loss?



• 
Hysteresis loss
• 
Heat loss

• 
Iron loss

• 
Eddy-current loss

How are fixed capacitors classified?



• 
By the thickness of their conductors

• 
By their dielectric materials

• 
By their plate size

• 
By the thickness of their dielectric materials

The value of current of an ac waveform taken at any particular moment of time is what type of value?



• 
Average value

• 
Effective value

• 
Instantaneous value 

• 
Peak-to-peak value

Which of the following actions will increase the capacitance of a capacitor?



• 
The plates are moved closer together 

• 
The plates are moved farther apart

• 
The dielectric constant is decreased

• 
Both 2 and 3 above

What is the symbol for inductance?



• 
L 

• 
XL

• 
H

• 
IND

What physical property is similar to inductance?



• 
Mass

• 
Motion

• 
Inertia
• 
Velocity

Which of the following factors will NOT affect the value of inductance of a coil?



• 
Diameter of the coil

• 
Core materials used

• 
Number of coil turns

• 
Conductor tensility

Which of the following properties surrounds a current-carrying conductor?



• 
An attractive force

• 
A repulsive force

• 
An electrostatic field

• 
A magnetic field

A waveform is a graphic plot of what quantities?



• 
Amplitude versus time

• 
Current versus time

• 
Magnitude versus amplitude

• 
Voltage versus amplitude

The left-hand rule for generators states that the thumb of the left hand points in the direction of motion of the



• 
induced current

• 
conductor
• 
generator poles

• 
magnetic field

Which of the following types of capacitors are referred to as self-healing?



• 
Ceramic

• 
Mica

• 
Paper

• 
Oil

Normally, most coils have cores composed of either air or



• 
carbon steel

• 
soft iron 

• 
carbon

• 
copper

If the radius of a coil is doubled, its inductance is increased by what factor?



• 
One

• 
Two

• 
Eight

• 
Four

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



• 
Inertia

• 
Electromotive
• 
Resistive

• 
Inductive

A capacitor is a device that stores energy in a/an



• 
molecular field

• 
induced field

• 
electrostatic field
• 
electromagnetic field

What term applies to the power loss in an iron core inductor due to the current induced in the core?



• 
Heat loss

• 
Eddy-current loss

• 
Hysteresis loss

• 
Iron loss

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?



• 
25.2%

• 
63.2%
• 
12.8%

• 
37.8%

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)?



• 
(a) Glass (b) Paraffin paper

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

• 
(a) Petroleum (b) Air

What is the symbol used to denote the basic unit of measurement for inductance?



• 
L

• 
F

• 
I

• 
H

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



• 
Changes in current 

• 
Changes in voltage

• 
Constant current

• 
Constant voltage

A soft iron core will increase inductance because it has which of the following characteristics?



• 
Low permeability and high reluctance

• 
Low permeability and low reluctance

• 
High permeability and low reluctance 

• 
High permeability and high reluctance

Alternating current has replaced direct current in modern transmission systems because it has which of the following advantages?



• 
Ac can be transmitted at lower voltage levels

• 
Ac can be readily stepped up or down 

• 
Ac can be transmitted with no line loss

• 
Ac can be transmitted at higher current levels

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?



• 
(a) Increase, (b) by 4 times

• 
(a) Decrease, (b) by 1/2 

• 
(a) Decrease, (b) by 1/4

• 
(a) Increase, (b) by 2 times

Self-induced emf is also known as what force?



• 
Counter electromotive force 

• 
Inertial force

• 
magnetic force

• 
Electromotive force

What is the unit of measurement for frequency?



•  
  Hertz

• 
Period

• 
Cycle

• 
Maxwell

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



• 
They are dislodged from orbit 

• 
They bunch up on one side of the nucleus

• 
They move closer to their nucleus

• 
They move closer to other orbiting electrons

What is the unit of measurement for inductance?



• 
Rel

• 
Farad

• 
Ohm

• 
Henry

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



• 
breaking voltage

• 
working voltage
• 
limiting voltage

• 
conduction voltage

Capacitance is defined as the property of a circuit that



• 
opposes a change in current

• 
aids a change in voltage

• 
opposes a change in voltage

• 
aids a change in current

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?



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

• 
A step-down transformer placed in series with load

• 
A resistor placed in parallel with the load

The property of inductance is present in which of the following electrical circuits?



• 
An ac circuit

• 
A dc circuit

• 
A resistive circuit

• 
Each of the above

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



• 
The amount of current flow through the coil

• 
The type of core material

• 
The number of turns in the conductor

• 
All of the above

What type of dielectric is LEAST sensitive to power dielectric-hysteresis losses?



• 
Pure water

• 
Air

• 
Mica

• 
Vacuum

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



• 
Dielectric hysteresis
• 
Plate loading

• 
Plate heating

• 
None of the above

Capacitance and inductance in a circuit are similar in which of the following ways?



• 
Both aid voltage

• 
Both prevent the storage of energy

• 
Both oppose current

• 
Both cause the storage of energy