Transcript M05

M053 Review for Units 1 and
2
1. What are other terms for rise
and decay of current and
voltage in a circuit?
Increase and decrease of current
and voltage in a circuit.
2. When does current reach its
maximum value in a resistive
circuit?
Instantly when the resistive
circuit is energized.
3. Which line represents time and
which line current in a time
graph?
The horizontal line represents
time and the vertical line
represents current.
4. What are time constants?
Marks on the time line that
show time periods.
5. On a time line, where does
the second time period begin?
At T1.
6. What do T0, T1, T2, T3, etc.,
refer to?
Time periods or time
constants.
7. What is an LR circuit?
A circuit that has both
inductance and resistance.
8. How many time periods does it
take for current in a LR circuit to
reach maximum value?
Five.
9. How many time constants
does it take for current in an LR
circuit to decay?
Five.
10. What is the abbreviation
for time constant?
TC.
11. What is the term used to
identify/measure time constants?
Milliseconds or microseconds.
12. What is the Universal Time
Constant Chart?
A graph which shows percentage
values on the rise and decay
curves at each of the five time
constants.
13. What is the mathematical
formula for time constants?
TC=L/R
14. What is a growth curve?
A curve that shows the rise of
current.
15. What is the percentage
value on a decay curve at T3?
5%.
16. What is the percentage
value on a growth curve at T4?
98%.
17. What is a capacitor?
An electrical device that stores
energy and then releases it later.
18. What are the two conducting
surfaces of a capacitor called?
Plates.
19. What is another term that is
often used instead of the word
“capacitor”?
Condenser.
20. What types of non-conducting
material can be used to separate
the plates of a capacitor?
Air, paper, or liquid.
21. When is a capacitor said
to be charged?
When it has potential difference
between the two plates.
22. What is capacitance?
The ability of two conducting
surfaces, separated by some
form of non-conducting material,
to store an electrical charge.
23. What factors determine the
capacitance of a capacitor?
1.
The surface are of the
plates., 2. The distance
between the plates., and 3.
The dielectric used between
the plates.
24. What effect does the amount
of voltage applied to a
capacitor have in the
capacitance?
No effect.
25. What happens to capacitance
if the plate areas of a capacitor
are doubled?
The capacitance is doubled.
26. What are dielectric
constants?
The numerical ratings given
dielectric materials based on their
relationship to air.
27. How do you find total
capacitance in a series circuit?
Use the same rule for
determining total resistance in a
parallel circuit.
28. What is capacitive
reactance?
The opposition to current flow
that a capacitor offers in an AC
circuit.
29. What is the unit of
measurement of capacitance?
The farad.
30. How many farads is a
picofarad?
1/1,000,000,000,000 of a
farad.
31. How is capacitive
reactance (XC) measured?
In ohms.
32. When will current flow stop in
a DC circuit with a capacitor
wired into it?
When capacitor voltage
equals applied voltage.
33. What is another name for
a vacuum tube?
An electron tube.
34. What do you call a tube from
which all of the air has been
removed?
A vacuum tube.
35. Which is the positive
electrode in a vacuum tube?
The anode.
36. What is the name of the
negative electrode in a vacuum
tube?
The cathode.
37. What is the name of the glass
or metal housing around a
vacuum tube?
An envelope.
38. What electronic elements are
found inside a vacuum tube?
Electrodes.
39. What is the giving off of
electrons from a heated cathode
called?
Emitting electrons.
40. What is another term for
cathode.
Emitter.
41. Which electrode is
sometimes called the emitter?
The cathode.
42. Which electrode is
sometimes called the collector?
The anode.
43. What is the heater wire in
a vacuum tube called?
A filament wire.
44. When is the cathode in a
vacuum tube said to be directly
heated?
When the cathode and the
filament are the same.
45. How many electrodes are
in a diode?
Two.
46. What is a triode?
A vacuum tube that has three
electrodes.
47. What is the wire screen in
a vacuum tube called?
A grid.
48. What does the control grid
do in a vacuum tube?
It controls the flow of electrons
from the cathode to the anode.
49. What are the electrodes in
a triode?
The cathode, the anode, and
the control grid.
50. What do you call a vacuum
tube with four electrodes?
A tetrode.
51. What are the four
electrodes in a tetrode?
The anode, the cathode, the
screen grid, and the control grid.
52. What is a pentode?
A vacuum tube which contains
five electrodes.
53. What are the five
electrodes in a pentode?
The cathode, the anode, the
control grid, the screen grid, and
the suppressor grid.
54. What can a vacuum tube
be used for?
To change AC current to DC and
to increase the strength of an
electrical signal.
55. How does a transistor
differ from a vacuum tube?
Transistors weigh less, are
smaller but stronger than vacuum
tubes, and require no warm-up
time.
56. What can very hot weather
do to a transistor?
It can cause the transistor to
stop working.
57. What are the three basic
parts of a transistor?
The emitter, the base, and the
collector.
58. What are two types of
materials that transistors are
made from?
P-type and N-type material.
59. What elements are in Ptype material?
Germanium and indium.
60. What part of a transistor is
comparable to the cathode in a
vacuum tube?
The emitter.
61. Where is the base of a
transistor located?
Between the emitter and the
collector.
62. What is the collector in a
transistor comparable to in a
vacuum tube?
An anode.
63. What is a PNP transistor?
One in which the emitter and
collector are made of P-type
material.
64. Which direction does current
flow in an NPN transistor?
From the emitter to the
collector.
65. What is the primary use of
a transistor?
As a current-, voltage-, or
power- amplifying device.
66. What does a rectifier do?
Changes alternating current to
pulsating direct current.
67. What is an amplifier?
An electronic component that
amplifies a signal.
68. What is gain?
The ratio of output to input
signal.
69. What is the simplest type
of amplifier?
A single-ended amplifier.
M053 Review for Units 3 and
4
1. What device transfers
electrical energy from one
circuit to another by
electromagnetic induction?
A transformer.
2. What type of transformer
transfers a high voltage to a low
voltage?
A step-down transformer.
3. What two types of cores are
used for transformers?
An iron core and an air core.
4. Does a transformer have an
AC or a DC source for
continuous output?
An AC source.
5. How does a transformer
transfer electrical energy from
one circuit to another?
By electromagnetic induction.
6. What are the main shapes
used for iron-core transformers?
Hollow core and shell.
7. What is another name for a
shell-type core?
E- and I- type core.
8. Which transformer core is
the most commonly used?
The shell-type core.
9. Which winding on a
transformer is connected to the
power source?
The primary winding.
10. What is the secondary
winding on a transformer connect
to?
The load.
11. What is the simplest type
of transformer winding?
The single-secondary
transformer.
12. When is a multi-secondary
transformer used?
When more than one voltage
is required.
13. What type of transformer
secondary has two equal outputs
of opposite polarity?
A center-tapped transformer.
14. What is a 1:1 ratio
transformer?
A transformer in which the source
voltage matches the voltage
required by the rest of the power
supply.
15. What kind of transformer loss
occurs as a result of the small
amount of resistance present in
any coil or wire?
Copper loss.
16. What can be done to
reduce copper loss?
Windings are made of lowresistance copper.
17. What do you call the power
loss caused by random current
flow within a core?
Eddy-current loss.
18. How are transformer cores
made in order to reduce eddycurrent loss?
They are made with laminated
slices of steel insulated with
varnish.
19. What is hysteresis loss?
The energy lost when aligning
the magnetic units within the core
when the field changes direction.
20. How does an increase in
frequency of the applied voltage
affect hysteresis loss?
A greater loss through heat
dissipation occurs when the
frequency of applied voltage is
increased.
21. What type of transformer core
is used to reduce hysteresis
loss?
Air cores.
22. What type of transformer core
is used with frequencies in the
audio range?
Iron cores.
23. What type of transformer loss
can be thought of as resulting
from a kind of friction?
Hysteresis loss.
24. What happens to current
when frequency is increased in a
transformer?
Current is decreased.
25. What is determined by the
type and thickness of the
insulation of the windings of a
transformer?
The voltage-handling capacity.
26. What determines the powerhandling capacity of a
transformer?
The cooling ability of the
transformer.
27. What is determined by the
diameter of the wire used in the
windings of a transformer?
The current-handling capacity.
28. What is indicated on the
front or side of a transformer?
The voltage-, current-, and
power- handling capacity.
29. What is a diode?
A device that allows current to
flow easily in one direction, but
offers opposition to current flow
in the other direction.
30. What is the function of a
rectifier in a circuit?
It converts AC voltage into
pulsating DC voltage.
31. When does reverse bias
exist?
When the cathode is more
positive than the anode.
32. What is an alternation?
Half of a cycle.
33. What is the key to rectifier
operation?
A diode.
34. What two alternations
does a cycle of AC have?
Positive and negative
alternation.
35. What does a half-wave
rectifier block?
Either the positive or negative
alternation of the AC circuit in the
transformer secondary.
36. What is negative pulsating
DC voltage?
The voltage produced from the
output of a rectifier when the
rectifier blocks the positive AC
half-cycles.
37. How many diodes does a
half wave rectifier have?
One.
38. What is the simplest
rectifier circuit?
A half-wave rectifier circuit.
39. What is positive pulsating
DC voltage?
The voltage produced from the
output of a rectifier when the
rectifier blocks the negative AC
half-cycle.
40. What does the diode block
in a half-wave rectifier?
Either the positive or negative
alternation of the AC current in
the secondary.
41. Which output voltage has
less variation, the output from a
full-wave rectifier, or the output
from a half wave rectifier?
Full-wave rectifier output
voltage.
42. How many diodes are
there in a full-wave rectifier?
Two.
43. Which rectifier uses two
diodes to convert each negative
and positive alternation of the
input AC voltage to one polarity
at the output?
A full-wave rectifier.
44. What does the center-tapped
transformer do in the transformer
secondary?
It splits the secondary AC voltage
into two equal AC voltages.
45. How many diodes are
conducting at a given time in a
bridge rectifier?
Two.
46. How many diodes does a
bridge rectifier have?
Four.
47. How are the diodes in a
bridge rectifier arranged?
In a diamond pattern.
48. What is the main advantage
of using a full-wave rectifier?
There is low voltage variation
in the output.
49. What is the main advantage
of using a bridge rectifier?
It has low voltage variation
and high voltage output.
50. What are the disadvantages
of a full-wave rectifier?
It has more components than a
half-wave rectifier, and it has low
output voltage.