Chapter 10: Inductance
MULTIPLE CHOICE
1. The opposition to the changes in current flow is identified as ____.
a.
electromotive force
c.
rate of change
b.
counter electromotive force
d.
inertia
2. The symbol for inductance is ____.
a.
H
c.
J
b.
I
d.
L
3. ____ inductors are created with adjustable core material.
a.
Fixed
c.
Magnetic
b.
Variable
d.
Nonmagnetic
4. ____ inductors, or inductors without core material, are used for up to 5 millihenries of inductance.
They are wrapped on a ceramic or phenolic core.
a.
Air-core
c.
Toroid-core
b.
Ferrite and powdered iron core
d.
Laminated iron-core
5. ____ inductors are referred to as chokes.
a.
Air-core
c.
Toroid-core
b.
Iron-core
d.
Shielded
6. ____ inductors offer a high inductance for a small size. The magnetic field is contained within the
core.
a.
Air-core
c.
Toroid-core
b.
Ferrite and powdered iron core
d.
Laminated iron-core
7. ____ inductors are used for all large inductors.
a.
Air-core
c.
Toroid-core
b.
Ferrite and powdered iron core
d.
Laminated iron-core
8. The total inductance of several inductors connected in series (separated to prevent their magnetic fields
from interacting) is found by using the formula ____.
a.
LT = L1 + L2 + L3 … + Ln
c.
LT = L1 * L2 * L3 … * Ln
b.
LT = L1 = L2 = L3 … = Ln
d.
1/LT = 1/L1 + 1/L2 + 1/L3 … + 1/Ln
9. If two or more inductors are connected in parallel (with no interaction of their magnetic fields) the
total inductance is found by using the formula ____.
a.
LT = L1 + L2 + L3 … + Ln
c.
LT = L1 * L2 * L3 … * Ln
b.
LT = L1 = L2 = L3 … = Ln
d.
1/LT = 1/L1 + 1/L2 + 1/L3 … + 1/Ln
10. A time constant is the time required for current to increase to ____ or decrease to ____ of the
maximum current.
a.
0.632%, 0.368%
c.
63.2%, 36.8%
b.
6.32%, 3.68%
d.
632%, 368%
COMPLETION
1. Once current is moving through a conductor, ____________________ helps to keep it moving.
2. Inductors consist of a(n) ____________________ coiled around a core.
3. ____________________ inductance occurs when the core material is in line with the coil of the wire.
SHORT ANSWER
1. Describe what transpires in a conductor when the current changes directions or stops, or the magnetic
field changes.
2. What are inductors? Briefly describe their basic components and classifications.
