17174A Inductance
An LR circuit contains a 150-ohm resistor and a 2-henry coil. What is the time value of one L/R time constant?
.0133 seconds
An LR circuit is composed of a coil of .5 henry and a 10-ohm resistor. The maximum current in the circuit is 5 amperes. After the circuit is energized, how long will it take for current to reach maximum value?
0.25 second
An electrical circuit contains three non coupled inductors of 3.3, 4.5, and 2 microhenries. What is the total inductance of the circuit?
0.98 microhenries
copper loss of an inductor can be calculated by the use of which formulas?
1 : P = I2R
if a coil is rated at 10 henries, what is its value in a milihenries and microhenries
10,000mH, 10,000,000
An LR circuit has a maximum current of 30 mA. At the end of the first time constant of the discharge cycle, what total current will be flowing in the circuit?
11 mA
An LR circuit has a time constant of .05 second and an inductor with a value of a 60 henry. What value of resistor is required?
12 ohms
An electrical circuit contains four non coupled inductors in a series configuration. The inductors have the following values (in microhenries): 2, 3.5, 6, 1. What is the total inductance (LT) of the circuit?
12.5 microhenries
an ac electrical current varies 1.5 amperes in one second and is applied to a 10-henry coil. What is the value of the emf induced across the coil
15.0 volts
the maximum current in an LR circuit is 20 amperes. What total current will be flowing in the circuit at the end of the second time constant of the charge cycle?
17.3 amperes
Two inductors of 3.6 and 7.3 microhenries are wired together in series and they aid each other. the mutual inductance for the circuit is 3.6 microhenries. what is the total inductance of the circuit?
18.1 microhenries
if 9 volts are induced in a conductor when the current changes by 4.5 amperes in one second, what is the total inductance of the circuit?
2 henries
an electrical circuit contains a coil. when the current varies 2.5 amperes in one second, 7.5 volts are induced in the coil. what is the value of inductance of the coil
3.0 henries
two coils have a coefficient of coupling of .7 and are related at 12 micro henries and 3 microheries respectively. What is their total mutual inductance?
4.2 microhenries
refer to the circuit described in question 2-43. circuit will increase by what amount during the second time constant?
4.7 amperes
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?
63.2%
Which of the following waveforms depicts growth current (l g) through the coil (L)
A
What waveform is an illustration of the voltage (ES) present across the voltage driver when switch S1 is closed?
C
The voltage developed across L when switch S1 is closed is depicted in what waveform?
E
what waveform depicts the voltage developed across R when switch S2 is closed?
F
Maximum current will flow in an LR circuit after a minimum of how many time constants have elapsed?
Five
The voltage dropped across R when switch is closed is depicted in which of the following waveforms?
G
What is the symbol used to denote the basic unit of measurement for inductance
H
What is the symbol for inductance?
L
when electrons are moved in a conductor by a magnetic field, a force known by which of the following terms is created?
all of the above
Inductors experience copper loss for what reason?
because all inductors have resistance which dissipates power
how are inductors classified
by core type
The property of inductance offers opposition to which of the following qualities?
changes in current
when switch S2 is closed, energy is supplied to the circuit by the...
collapsing magnetic field of L1
the left-hand rule for generators states that the thumb of the left hand points in the direction of the...
conductor
Which of the following factors will NOT affect the value of the inductance of a coil?
core materials used
Self-induced emf is also known as what force?
counter-electromotive force
if the length of a coil is doubled while the number of turns is kept the same, this will have what effect on inductance and by what factor?
decrease, by 1/2
the property of inductance is present in which of the following electrical circuits?
each of the above
What term applies to the power loss in an iron core inductor due to the current induced in the core?
eddy-current loss
the difference in potential across a resistor, created by current through the resistor is an example of which of the following forces?
electromotive
In the first instant when switch S1 is closed, the entire battery-voltage is used to overcome the...
emf developed in L
IF a coil is wound in layers, its inductance will be greater than that of a similar single-layer coil because of a higher...
flux linkage
Regardless of the method used, inductance of a coil can ONLY be increased by increasing what coil characteristic
flux linkage
When the number of turns is increased in a coil from 2 to 4, the total inductance will increase by a factor of...
four
if the radius of a coil is doubled, its inductance is increased by what factor?
four
What is the unit of measurement for inductance
henry
power consumed by an iron core inductor in reversing the magnetic field of the core is termed as what type of loss?
hysteresis loss
what physical property is similar to inductance
inertia
According to Lenz's Law, the induced emf produced by a change in current in an inductive circuit tends to have what effect on the current?
it opposes either a rise or a fall in current
why do large coils have greater inductance that smaller diameter coils, all other factors being the same?
large diameter coils have more wire and thus more flux
an increase in the permeability of the core of a coil will increase which of the following core characteristics
magnetic flux
during the first instant when switch S1 is closed, current is maximum in which, if any, of the following parts of the h circuit?
none of the above
mutual inductance between two coils is affected by which of the following factors?
physical dimensions of the coils
normally, most coils have cores composed of either air or..
soft iron
During the first instant when switch S1 is closed, maximum voltage is dropped across...
the coil
when source voltage is removed from a current-carrying conductor, a voltage will be induced in the conductor by which of the following actions?
the collapsing magnetic field
the coefficient of coupling between two coils is a measure of what factor?
the magnetic flux radio linking the coils
What does the Greek letter Delta signify as in triangle-l or triangle t
the values are changing
When a magnetic field moves through a stationary conductor, the electrons in orbit are affected in what manner?
they are dislodged from orbit
The hollow form of nonmagnetic material found in the center of an air core coil has what purpose?
to support the windings
when does mutual inductance occur between inductors
whenever the flux of one inductor causes an emf to be induced in another inductor
