11931679
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Quiz von Andrew Best, aktualisiert more than 1 year ago
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Erstellt von Andrew Best
vor mehr als 6 Jahre
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Frage 1
Frage
The Tesla (T) and the Gauss (G) are both units for magnetic flux destiny.
Antworten
- True
- False
Frage 2
Frage
The Unit for measuring magnet-motive force (mmf) is the volt.
Antworten
- True
- False
Frage 3
Frage
Ohm's law for a magnetic circuit gives the relationship between flux destiny, magnet-motive force, and reluctance.
Antworten
- True
- False
Frage 4
Frage
A Solenoid is a form of electromagnetic switch that opens and closes mechanical contacts.
Antworten
- True
- False
Frage 5
Frage
A hysteresis curve is a plot of flux density (B) as a function of field intensity (H).
Antworten
- True
- False
Frage 6
Frage
To produce an induced voltage in a coil, the magnetic field surrounding can be changed.
Antworten
- True
- False
Frage 7
Frage
The speed of a generator can be controlled with a rheostat in the field winding's.
Antworten
- True
- False
Frage 8
Frage
A self-excited dc generator will normally have enough residual magnetism in the the field magnets to start the generator producing voltage at the output when it is first turned on.
Antworten
- True
- False
Frage 9
Frage
The power developed by a motor is proportional to its torque.
Antworten
- True
- False
Frage 10
Frage
In a brushless motor, the magnetic field is supplied by permanent magnets.
Antworten
- True
- False
Frage 11
Frage
The period of a 60 Hz sine is 16.7 ms.
Antworten
- True
- False
Frage 12
Frage
The rms and average value of a sine wave are the same.
Antworten
- True
- False
Frage 13
Frage
A sine wave with a peak value of 10 V has the same heating effect as a 10 V dc source.
Antworten
- True
- False
Frage 14
Frage
The peak value of a sine wave is the same as its amplitude.
Antworten
- True
- False
Frage 15
Frage
The number of radians in 360 degrees is 2π.
Antworten
- True
- False
Frage 16
Frage
In a three-phase electrical system, the phases are separated by 60°
Antworten
- True
- False
Frage 17
Frage
The purpose of an exciter is to supply dc rotor current to an alternator.
Antworten
- True
- False
Frage 18
Frage
In an automotive alternator, the output current is taken from the rotor through slip rings.
Antworten
- True
- False
Frage 19
Frage
A maintenance issue with induction motors is brush replacement.
Antworten
- True
- False
Frage 20
Frage
A synchronous motor can be used when constant speed is required.
Antworten
- True
- False
Frage 21
Frage
When the south poles of two bar magnets are brought close together, there will be
Antworten
-
a force of attraction
-
a force of repulsion
-
an upward force
-
no force
Frage 22
Frage
A magnetic field is made up of
Antworten
-
positive and negative charges
-
magnetic domains
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flux lines
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magnetic poles
Frage 23
Frage
the Direction of a magnetic field is from
Antworten
-
north pole to south pole
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south pole to north pole
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inside to outside the magnet
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front to back
Frage 24
Frage
Reluctance in a magnetic circuit is analogous to
Antworten
-
voltage in an electric circuit
-
current in an electric circuit
-
power in a electric circuit
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resistance in a electric circuit
Frage 25
Frage
The unit of magnetic flux is
Antworten
-
tesla
-
weber
-
ampere-turn
-
ampere-turns/weber
Frage 26
Frage
The unit of magneto-motive force is the
Antworten
-
tesla
-
weber
-
ampere-turn
-
ampere-turns/ weber
Frage 27
Frage
The unit of flux density is the
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-
tesla
-
weber
-
ampere-turn
-
electron-volt
Frage 28
Frage
The electromagnetic activation of a movable shaft is the basis for
Antworten
-
relays
-
circuit breakers
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magnetic switches
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solenoids
Frage 29
Frage
When there is current through a wire placed in a magnetic field,
Antworten
-
the wire will overheat
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the wire will become magnetized
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a force is exerted on the wire
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the magnetic field will be cancelled
Frage 30
Frage
A coil of wire is placed on a changing magnetic field. if the number of turns ion the coil is increased, the voltage induced across the coil will
Antworten
-
remain unchanged
-
decrease
-
increase
-
be excessive
Frage 31
Frage
if a conductor is moved back and forth at a constant rate in a constant magnetic field, the voltage induced in the conductor will
Antworten
-
remain constant
-
reverse polarity
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be reduced
-
be increased
Frage 32
Frage
In the crankshaft position sensor in figure 10-33, the induced voltage across the coil is caused by
Antworten
-
a current in the coil
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rotation of the steel disk
-
a tab passing through the magnetic field
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acceleration of the steel disks rotational speed
Frage 33
Frage
The purpose of the commutator in a generator or motor is to
Antworten
-
change the direction of the current to the rotor as it spins
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change the direction of the current to the stator winding's
-
support the motor or generator shaft
-
provide the magnetic field for the motor or generator
Frage 34
Frage
In a motor, back emf serves to
Antworten
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increase power from the motor
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decrease flux
-
increase the current in the field windings
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decrease the current in the armature
Frage 35
Frage
The torque of a motor is proportional to the
Antworten
-
amount of flux
-
armature current
-
both of the above
-
none of the above
Frage 36
Frage
The difference between alternating current (AC) and direct current (DC) is
Antworten
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ac changes value and dc does not
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ac changes direction and dc does not
-
both answers A and B
-
neither answers A and B
Frage 37
Frage
During each cycle, a sine wave reaches a peak value
Antworten
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one time
-
two times
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four times
-
a number of times depending on the frequency
Frage 38
Frage
A sine wave with a frequency of 12 kHz is changing at a faster rate than a sine wave with a frequency of
Antworten
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20 kHz
-
15,000 Hz
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10,000 Hz
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1.25 MHz
Frage 39
Frage
A sine wave with a period of 2 ms is changing at a faster rate than a sine wave with a period of
Antworten
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1 ms
-
0.0025 s
-
1.5 ms
-
1200 ms
Frage 40
Frage
when a sine wave has a frequency of 60 Hz, in 10 s it goes through
Antworten
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6 cycles
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10 cycles
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1/16 cycle
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600 cycles
Frage 41
Frage
if the peak value of a sine wave is 10 V, the peak-to-peak value is
Antworten
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20 V
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5V
-
100V
-
none of these
Frage 42
Frage
I the peak value of a sine wave is 20V, the rms value is
Antworten
-
14.14 V
-
6.37 V
-
7.07 V
-
5 V
Frage 43
Frage
The average value of a 10 V peak sine wave over one complete cycle is
Antworten
-
0 V
-
6.37 V
-
7.07 V
-
5 V
Frage 44
Frage
The average half-cycle value of a sine wave with a 20 V peak is
Antworten
-
0 V
-
6.37 V
-
12.74 V
-
14.14 V
Frage 45
Frage
One sine wave has positive-going zero crossing at 10° and another sine wave has a postive going zero crossing at 45°. The phase angle between the two wave-forms is
Antworten
-
55°
-
35°
-
0°
-
none of these
Frage 46
Frage
The instantaneous value of a 15 A peak sine wave point at a 32° from its postive-going zero crossing is
Antworten
-
7.95 A
-
7.5 A
-
2.13 A
-
7.95 V
Frage 47
Frage
A phasor represents
Antworten
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thew magnitude of a quantity
-
the magnitude and direction of a quantity
-
the phase angle
-
the length quantity
Frage 48
Frage
if the rms current through a 10kΩ resistor is 5 mA, the rms voltage drop across the resistors is
Antworten
-
70.7 V
-
7.07 V
-
5 V
-
50V
Frage 49
Frage
Two series resistors are connected to an AC source, If there are 6.5 V rms across one resistor and 3.2 V rms across the other, the peak source voltage is
Antworten
-
9.7 V
-
9.19 V
-
13.72 V
-
4.53 V
Frage 50
Frage
An advatage of a three-phase induction motor is that it
Antworten
-
maintains constant speed at any load
-
does not require starting winding's
-
has a wound rotor
-
all of the above
Frage 51
Frage
The difference in the synchronous speed of the stator field and the rotor speed of the motor is called
Antworten
-
differential speed
-
loading
-
lag
-
slip
Frage 52
Frage
a 10kHz pulse waveform consists of pulses that are 10us wide. Its duty cycle is
Antworten
-
100%
-
10%
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1%
-
not determinable
Frage 53
Frage
The duty cycle of a square wave
Antworten
-
varies wit the frequency
-
varies with the pulse width
-
both answers A and B
-
is 50%
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