更多"When voltage and current developed "的相关试题:
[单项选择]The voltage developed by an AC generator is controlled by varying the （）
A. speed of the prime mover
B. AC excitation to the field
C. DC excitation to the field
D. DC excitation of the voltage regulator
[单项选择]When measuring AC current flow, you must always connect the meter （）
A. in series with the power source and load
B. in parallel with the power source and load
C. insuring correct polarity
D. using the lowest range possible to prevent instrument damage
[单项选择]When current and voltage reach maximum values at the same time, the power factor is（）
A. minimum
B. maximum
C. leading
D. lagging
[单项选择]When the current flow through a copper wire increases, its （）
A. resistance will decrease
B. insulation will bum
C. temperature will increase
D. conductivity will increase
[单项选择]The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains （）.
A. a magnetic operating coil
B. normally open line contacts
C. thermal-overload protection
D. a momentary-contact start button
[单项选择]The term flood current refers to that time when the water（）.
A. is flowing towards the land
B. is moving towards the ocean
C. level is not changing
D. level is rising because of heavy rains
[单项选择]The part of a fuse that melts and opens the circuit is made of （）.
A. copper and antimony
B. steel and babbitt
C. aluminum or beryllium alloy
D. zinc or an alloy of tin and lead
[单项选择]When the current in a power transmission line is increased, the power loss （）
A. increases as the square of the current
B. decreases as the square root of the current
C. remains the same, as it is independent of current flow
D. increases in direct proportion as the current
[单项选择]When two AC generators are being paralleled, the breaker should be closed with the synchroscope pointer mating in the （）
A. "slow" direction, just before the 12 o'clock position
B. "fast" direction, just after the 12 o'clock position
C. "fast" direction, just before the 12 o'clock position
D. "slow" direction, just after the 12 o'clock position
[单项选择]When paralleling two AC generators, the frequency of the machine coming on-line, immediately prior to closing its breaker, should be （）
A. slightly less than the oncoming generator frequency
B. the same as the bus frequency
C. slightly greater than the bus frequency
D. the same as the bus voltage
[单项选择]When paralleled, AC generators must have the same （）
A. frequency
B. number of phases
C. phase rotation
D. All of the above
[单项选择]Universal motors will operate on AC or DC current, and are generally found in （）
A. portable tools
B. large pump motors
C. turbo electric main motors
D. forced draft fans
[单项选择]When securing an AC generator, you should FIRST （）.
A. open the generator circuit breaker
B. switch the voltage regulator to “manual”
C. decrease the field excitation to minimum
D. reduce the load on the unit
[单项选择]When can routine communications be resumed when radio silence has been imposed?（）
A. After determining that the frequency or channel appears to be no longer in use
B. After determining that geographic distance from the distress situation will prohibit any other signal from interfering with emergency communications
C. Routine communications can resume after the Rescue Coordination Center transmits a message on the frequency or channel being used for emergency communications stating that such traffic has concluded
D. If，in the Master's opinion，communications on that frequency will interfere with emergency communications
[填空题]It is
when
you nearly lose someone
when
you become
fully
conscious of how much you value
them
.
[单项选择]The alternating current generator supplying a load has a voltage drop resulted from the loadWhen the load has a lagging power factor this voltage drop （）.
A. is small
B. may be neglected
C. is useful
D. is considerable
[单项选择]The frequency of the alternating current generated by a synchronous generator is governed by the speed and the（）
A. full excitation
B. load
C. power factor
D. number of poles
[单项选择]Current measuring instruments must always be connected in （）
A. series with a circuit
B. parallel with a circuit
C. series-parallel with a circuit
D. delta with the shunt
[单项选择]Current refers to the（）.
A. vertical movement of the water
B. horizontal movement of the water
C. density changes in the water
D. None of the above
