Match the term that completes the following statements.
The direction of induced ? flow through a conductor is determined by
the direction of the magnetic field surrounding the conductor and the
direction the conductor is traveling through the magnetic field.
Whenever a conductor cuts through magnetic lines of flux, a ? is induced into the conductor.
Whenever current flows through a conductor, a ? is created around the
conductor.
Possible Answers
voltage
current
magnetic field
current
voltage
magnetic field
When no current flows in a conductor, free electrons move ? , and their magnetic fields
cancel.
a.
at random
b.
from negative to positive
c.
from positive to negative
d.
from source to load
The correct answer is: at random
When current flows in a conductor, a magnetic field is produced. As free electrons move in
one direction, their individual magnetic fields ? .
a.
add together
b.
collapse
c.
flow together
d.
subtract from each other
The correct answer is: add together
The important factors needed for generation of an induced voltage are a conductor, a
magnetic field, and ? .
a.
current
b.
poles
c.
relative motion
d.
voltage
The correct answer is: relative motion
Select the correct option to complete the following sentences.
As current flow decreases, the magnetic field surrounding the conductor
will ? .
As the current passing through a coil increases, the magnetic field
around the coil will ? .
Possible Answers
increase
decrease
decrease
increase
When a conductor moves through a stationary magnetic field an EMF is induced, but when the
magnetic field moves and the conductor remains stationary no EMF is induced.
Select one:
True
False
The correct answer is 'False'.
Whenever an electric current flows through a conductor, a magnetic field is formed ? the
conductor.
a.
above
b.
around
c.
below
d.
inside
The correct answer is: around
? Law states that an induced voltage or current opposes the motion that causes the induced
voltage or current.
a.
Fleming's
b.
Henry's
c.
Lenz's
d.
Tesla's
The correct answer is: Lenz's
Inductors always oppose a change of ? .
a.
current
b.
polarity
c.
resistance
d.
voltage
The correct answer is: current
Counter Electromotive Force is sometimes called back EMF, and CEMF is ? out-of-phase with
the applied voltage.
a.
90°
b.
180°
c.
270°
d.
360°
The correct answer is: 180°
CEMF ? the applied EMF when current is increasing and ? the applied EMF when current is
decreasing.
a.
adds to / subtracts from
b.
blocks / passes
c.
subtracts from / adds to
The correct answer is: subtracts from / adds to
Which items listed below are factors that work in combination to affect the inductance
produced by an inductor.
I. Cross sectional area of the core
II. Number of turns of wire
III. Permeability of the core material
IV. Spacing between the turns
a.
I., II., III.
b.
II., III., IV.
c.
I., III., IV.
d.
I., II., III., IV.
The correct answer is: I., II., III., IV.
Question 13
Drag the appropriate term to the correct schematic symbol.
picture is the answer
The rate of current change in an inductive circuit can be described as a(n) ? curve.
a.
ascending
b.
descending
c.
exponential
d.
sine
The correct answer is: exponential
How many time constants does it take for current to reach its maximum value in an inductive
circuit?
a.
3
b.
5
c.
63.2
d.
180
The correct answer is: 5
At what percentage is the current after one time constant when the circuit is first energized?
a.
32.6% of maximum
b.
36.2% of maximum
c.
62.3% of maximum
d.
63.2% of maximum
The correct answer is: 63.2% of maximum
The unit of inductance is the ? , and inductance is represented by the letter ? .
a.
henry / L
b.
hertz / I
c.
lenz / L
d.
ohm / I
The correct answer is: henry / L
If a change of one ampere in one second causes one volt to be induced, you have ? of
inductance.
a.
one henry
b.
one ohm
c.
two henries
d.
two ohms
The correct answer is: one henry
In high frequency applications, ? inductors are used because of eddy current loss and
hysteresis loss in the core material.
a.
air core
b.
hollow core
c.
iron core
d.
solid core
The correct answer is: air core
In the formula for inductance, match the letter to what it represents.
Cross sectional area of the core
Length of the core used
Number of turns of wire
Permeability of the type of core material used
Possible Answers
I
N
A
µ
A
l
N
µ
Match the term that completes the following statements.
Inductance will ? with an increase in the cross sectional area of the core.
Inductance is ? proportional to the length of the core used.
Inductance will ? with an increase in the number of turns of wire.
Inductance is ? proportional to the permeability of the type of core material used.
Possible Answers
inversely
directly
increase
increase
inversely
increase
directly
What is the formula for determining the time constant in an inductive circuit?
a. T= L x R
b. T= √L/R
c. T= R/L
d. T=L/R
The correct answer is: T=L/R
Calculate the amount of time it will take for the current to reach its maximum value in a circuit having 125 millihenries of inductance and 50 ohms of resistance.
The correct answer is: 0.0125 seconds
The circuit shown has a total current of 3 amperes. What is the approximate current at two time constants (I )?
a.
1.90 A
b.
2.59 A
c.
2.85 A
d.
2.94 A
The correct answer is: 2.59 A
Given the formula for determining the counter EMF (induced voltage of a coil), drag the
variables to the statement they represent.
picture is the answer