Stationary Engineer Electric study guide
questions with complete solution
graded A+
The power factor of a load is equal to the ____________ power divided by the ____________
power. - ANS True ; apparent
A 10-ohms and 20-ohms resistor are connected in parallel. The total line current drawn by this
parallel combination is 30 amps. Under these conditions, the line voltage will be ____________
volts. - ANS 200
A 20-ohm resistor is connected in series with a parallel combination of two resistors, one of
which is 10-ohms, the other 40-ohms. If the voltage across the parallel combination is 40 volts,
the voltage across the 20-ohm series resistor is ________ volts. - ANS 100
A certain 120-volts single-phase AC circuit has a power factor of 80 percent and a watt-meter
reading of 1150 watts. The current drawn by the circuit is _________ amperes. - ANS 12
If the voltage between lines of a 3-phase, 3-wire delta connected system is 2400 volts, then the
phase voltage is _____________ volts - ANS 2400
A circuit consists of an inductive reactance of 15 ohms and a resistor of 20 ohms in series
across a 100-volts, 60 cycles AC supply. The current in this circuit is ____________ amperes. -
ANS 4
A 3 phase, 3 wire, 208 volt, 60 cycles AC service supplies a balanced load consisting of three
30 ohms resistors connected wye. The line current under these conditions os MOST NEARLY
___________ amperes. - ANS 6
If the level of the electrolyte in a lead acid storage battery falls below the top of the plates
because of evaporations under normal operating conditions, it is BEST to add - ANS Water
A 600 volt cartridge fuse must have knife blade contacts if its current rating exceeds
_____________ amperes. - ANS 60
When the magnitude of the short circuit currents in a feeder circuit must be limited, this is
USUALLY accomplished by means of - ANS reactors
,The cross sectional area in circular mils of a standard cable having 37 strands, each of which ha
a diameter of 90 nils, is MOST NEARLY - ANS 300,000
A coil having an average diameter of 4 inches is to be made up from a 1,260 ft long length of
wire. The numbers of turns in this coil will be MOST NEARLY - ANS 1,200
An AC circuit consists only of a pure inductance and a power source. The relationship between
the voltage and the current in this circuit is that the - ANS current lags the voltage
The device commonly known as a growler is FREQUENTLY used to - ANS test DC armature
windings for shorts
When a megger is applied alternately to the two leads of a direct current electrolytic capacitor,
the reading will - ANS start at zero but increase gradually for one of the connections
The device used to convert direct current to alternating current is called - ANS inverters
Of the following conditions, the one which is MOST likely to cause flashing or excessive arcing
from brush to brush in a motor is - ANS Excessively high voltage on the line
The currents in the armature equalizer connections in a DC generator are - ANS alternating
currents
A generating station has one 1000 Kw and two 2000 Kw generators. To supply 2000 Kw MOST
economically, the operating conditions should be - ANS one 2000 Kw generator at full load
The terminal voltage of a DC shunt generator having an armature current of 100 amperes, an
armature resistance of 0.02 ohms, and a generated E.M.F of 222 volts is MOST NEARLY
______________ volts. - ANS 220
The number of poles in the field of an alternator generating voltage at a frequency of 60 cycles
per second while rotating at 1200 rpm is - ANS 6
If the field of a shunt motor opens while running, the motor will - ANS run away
To reverse the direction of rotation of a cumulative compound motor, and not have it run as a
differential compound motor, reverse the connections to the ____________ field. - ANS shunt
field and to the series
A main contributing factor to motor stator failure usually is - ANS dirt
The input of a motor is 40,000 watts and efficiency is 80 percent. The TOTAL energy loss is
__________ watts. - ANS 8,000
, The full load current of a three-phase 5 hp motor operating at 200 volts, 60 cycles, and having
an efficiency of 80 percent and a power factor of 85 percent is MOST NEARLY ____________
amperes. - ANS 14.4
Of the following motors, the one that has the best speed regulation is the motor. - ANS shunt
The full load speed of a 60-cycle 208 volt, 3 phase induction motor having 6 poles and operating
with a slip of 10% is MOST NEARLY___________ r.p.m - ANS 1080
Of the following, a MAJOR advantage of an AC synchronous motor is that it(s) - ANS can be
used for power factor correction
If the field current of a synchronous motor is increased to a point which makes the synchronous
motor overexcited, the - ANS motor will take a leading current
When transformers are to be operated in parallel, it is NOT necessary that the transformer have
the same - ANS KVA rating
A transformer rates at 200 KVA is FULLY loaded with a lagging power factor of 80% when it is
supplying - ANS 160 KW
If the current in the primary of a current transformer is 500 amperes and the transformer has a
ratio of 100 to 5, an ammeter connected to the secondary will read MOST
NEARLY___________ amperes. - ANS 25
Assume that a switchboard ammeter which is connected to a current transformer is damaged
and must be removed without interrupting the service. Of the following, an ESSENTIAL
precaution to be taken before disconnecting the ammeter is to - ANS short the secondary of the
transformer
A DC relay is rated at 6 volts and 120 ohms. This relay can be operated from a 120 volt line by
connecting a ___________ ohm resistance in __________ with relay - ANS 2280: series
Some relays are provided with dash-pots. The FUNCTION of these dash-pots is to provide -
ANS delayed time action
An ammeter has a full scale deflection for a current of 0.01 amperes and an internal resistance
of 20 ohms. In order to have the ammeter read full-scale for a current of 10 amperes and not
damage its movement, a shunt should be used having a value of__________ ohms. - ANS
0.02
An air circuit breaker has contacts that flash. The MOST probable cause of this trouble is that
the - ANS barriers are broken
questions with complete solution
graded A+
The power factor of a load is equal to the ____________ power divided by the ____________
power. - ANS True ; apparent
A 10-ohms and 20-ohms resistor are connected in parallel. The total line current drawn by this
parallel combination is 30 amps. Under these conditions, the line voltage will be ____________
volts. - ANS 200
A 20-ohm resistor is connected in series with a parallel combination of two resistors, one of
which is 10-ohms, the other 40-ohms. If the voltage across the parallel combination is 40 volts,
the voltage across the 20-ohm series resistor is ________ volts. - ANS 100
A certain 120-volts single-phase AC circuit has a power factor of 80 percent and a watt-meter
reading of 1150 watts. The current drawn by the circuit is _________ amperes. - ANS 12
If the voltage between lines of a 3-phase, 3-wire delta connected system is 2400 volts, then the
phase voltage is _____________ volts - ANS 2400
A circuit consists of an inductive reactance of 15 ohms and a resistor of 20 ohms in series
across a 100-volts, 60 cycles AC supply. The current in this circuit is ____________ amperes. -
ANS 4
A 3 phase, 3 wire, 208 volt, 60 cycles AC service supplies a balanced load consisting of three
30 ohms resistors connected wye. The line current under these conditions os MOST NEARLY
___________ amperes. - ANS 6
If the level of the electrolyte in a lead acid storage battery falls below the top of the plates
because of evaporations under normal operating conditions, it is BEST to add - ANS Water
A 600 volt cartridge fuse must have knife blade contacts if its current rating exceeds
_____________ amperes. - ANS 60
When the magnitude of the short circuit currents in a feeder circuit must be limited, this is
USUALLY accomplished by means of - ANS reactors
,The cross sectional area in circular mils of a standard cable having 37 strands, each of which ha
a diameter of 90 nils, is MOST NEARLY - ANS 300,000
A coil having an average diameter of 4 inches is to be made up from a 1,260 ft long length of
wire. The numbers of turns in this coil will be MOST NEARLY - ANS 1,200
An AC circuit consists only of a pure inductance and a power source. The relationship between
the voltage and the current in this circuit is that the - ANS current lags the voltage
The device commonly known as a growler is FREQUENTLY used to - ANS test DC armature
windings for shorts
When a megger is applied alternately to the two leads of a direct current electrolytic capacitor,
the reading will - ANS start at zero but increase gradually for one of the connections
The device used to convert direct current to alternating current is called - ANS inverters
Of the following conditions, the one which is MOST likely to cause flashing or excessive arcing
from brush to brush in a motor is - ANS Excessively high voltage on the line
The currents in the armature equalizer connections in a DC generator are - ANS alternating
currents
A generating station has one 1000 Kw and two 2000 Kw generators. To supply 2000 Kw MOST
economically, the operating conditions should be - ANS one 2000 Kw generator at full load
The terminal voltage of a DC shunt generator having an armature current of 100 amperes, an
armature resistance of 0.02 ohms, and a generated E.M.F of 222 volts is MOST NEARLY
______________ volts. - ANS 220
The number of poles in the field of an alternator generating voltage at a frequency of 60 cycles
per second while rotating at 1200 rpm is - ANS 6
If the field of a shunt motor opens while running, the motor will - ANS run away
To reverse the direction of rotation of a cumulative compound motor, and not have it run as a
differential compound motor, reverse the connections to the ____________ field. - ANS shunt
field and to the series
A main contributing factor to motor stator failure usually is - ANS dirt
The input of a motor is 40,000 watts and efficiency is 80 percent. The TOTAL energy loss is
__________ watts. - ANS 8,000
, The full load current of a three-phase 5 hp motor operating at 200 volts, 60 cycles, and having
an efficiency of 80 percent and a power factor of 85 percent is MOST NEARLY ____________
amperes. - ANS 14.4
Of the following motors, the one that has the best speed regulation is the motor. - ANS shunt
The full load speed of a 60-cycle 208 volt, 3 phase induction motor having 6 poles and operating
with a slip of 10% is MOST NEARLY___________ r.p.m - ANS 1080
Of the following, a MAJOR advantage of an AC synchronous motor is that it(s) - ANS can be
used for power factor correction
If the field current of a synchronous motor is increased to a point which makes the synchronous
motor overexcited, the - ANS motor will take a leading current
When transformers are to be operated in parallel, it is NOT necessary that the transformer have
the same - ANS KVA rating
A transformer rates at 200 KVA is FULLY loaded with a lagging power factor of 80% when it is
supplying - ANS 160 KW
If the current in the primary of a current transformer is 500 amperes and the transformer has a
ratio of 100 to 5, an ammeter connected to the secondary will read MOST
NEARLY___________ amperes. - ANS 25
Assume that a switchboard ammeter which is connected to a current transformer is damaged
and must be removed without interrupting the service. Of the following, an ESSENTIAL
precaution to be taken before disconnecting the ammeter is to - ANS short the secondary of the
transformer
A DC relay is rated at 6 volts and 120 ohms. This relay can be operated from a 120 volt line by
connecting a ___________ ohm resistance in __________ with relay - ANS 2280: series
Some relays are provided with dash-pots. The FUNCTION of these dash-pots is to provide -
ANS delayed time action
An ammeter has a full scale deflection for a current of 0.01 amperes and an internal resistance
of 20 ohms. In order to have the ammeter read full-scale for a current of 10 amperes and not
damage its movement, a shunt should be used having a value of__________ ohms. - ANS
0.02
An air circuit breaker has contacts that flash. The MOST probable cause of this trouble is that
the - ANS barriers are broken
