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WorksheetsEE PART 5 - GERALDINO REVIEWER
Total questions: 200
Worksheet time: 2hrs 40mins
Which one is an advantage of a secondary cell over primary cell?
A. It can be recharge
B. It is portable
C. It is smaller in size
D. It has a higher capacity
During charging of a lead acid battery, what happens to the specific gravity of the electrolyte?
A. It will decrease
B. It will increase
C. It remains the same
D. It will become zero
When the electrolyte of a storage battery is low, what will a technician usually do?
A. Top up or add distilled water to the electrolyte
B. Drain the battery electrolyte and fill it with new
C. Charge the battery first before adding electrolyte
D. Add a special acid solution to the electrolyte
A lead acid cell should never be discharged beyon what voltage level?
A. 2.0 V
B. 1.5 V
C. 1.8 V
D. 1.0 V
What is the form of energy stored in a lead-acid battery?
A. Chemical energy
B. Solar energy
C. Electro-mechanical energy
D. Electrostatic energy
The capacity of a lead-acid cell does not depend on which of the following?
A. Rate of discharge
B. Quantity of the active material
C. Temperature
D. Rate of charge
What is the purpose of using distilled water in the electrolytes of a lead-acid cell?
A. It speeds up electrochemical action
B. It improves the specific gravity
C. It prevent or slows down local action
D. It prevents polarization of the battery
Which of the following cells should never be used until it dies?
A. Nickel-based
B. Mercury
C. Silver-oxide
D. Lead-acid
The capacity of a battery is expressed in which of the following units?
A. watt-hour
B. ampere-hour
C. voltage
D. current
A rechargeable battery is sometimes called .
A. primary cell
B. secondary cell
C. dry cell
D. voltaic cell
What is the advantage of the iron-nickel battery over the lead acid battery?
A. It needs less maintenance
B. It is much cheaper in cost
C. The output voltage is much higher
D. Its efficiency is much higher
The electrolyte in a storage battery is formed by which of the following?
A. Adding sulphuric acid to water
B. Adding water to sulphuric acid
C. Adding water to hydrochloric acid
D. Adding hydrochloric acid to water
The level of the electrolyte in a cell should be the level of plates.
A. above
B. below
C. equal to
D. any of these, depending on type of plates
The life of a storage battery is generally measured in terms of the number of .
A. cells it contains
B. plates it contains
C. Ah it can deliver
D. times it can be cycled
What type of cells is used by satellites?
A. Lead-acid cells
B. Carbon-zinc cells
C. Solar cells
D. Nickel-cadmium cells
What is the purpose of connecting cells in parallel?
A. To increase the output voltage
B. To increase the current capacity
C. To increase the internal resistance
D. To decrease the current capacity
The current in a chemical cell is a movement of .
A. positive hole charges
B. positive and negative ions
C. positive ions only
D. negative ions only
Where would you most likely to find a lead-acid battery?
A. In an LCD wall clock
B. In a flashlight
C. In a portable audio CD player
D. In an uninterruptible power supply
Which of the following statements is true during charging of a lead-acid cell?
A. It gives out energy
B. The voltage output will increases
C. The specific gravity of the electrolyte will decrease
D. Its cathode will become dark chocolate in color
The electrical conductivity in liquid solutions depends on which of the following?
A. Neutrons
B. Ions
C. Protons
D. Molecules
In a lead-acid cell, the term "internal resistance" is mainly due to which of the following?
A. Positive plate
B . Negative plate
C. Both positive and negative plates
D. Electrolytes
Which of the following is used to measure the specific gravity of the electrolyte in a battery?
A. Hydrometer
B. Manometer
C. Mechanical gauge
D. Psychrometer
An interactive solar power system .
A. lets the batteries recharge at night
B. power lights but not electronic devices
C. is totally independent from the electric company
D. allows home owners to sell power to the electric company
How do you call the positive electrode of a battery?
A. Anode
B. Voltaic node
C. Cathode
D. Base terminal
Which of the following is a primary cell?
A. Lead-acid cell
B. Mercury-oxide cell
C. Nickel-iron-alkaline cell
D. Nickel-cadmium-alkaline cell
What is the purpose of connecting cells in series- parallel?
A. To increase the output voltage
B. To increase the current capacity
C. Both A and B
D. None of these, because it never happens
Which one is the usual usage of the Weston cell?
A. A voltage reference source
B. A power reference source
C. A current reference source
D. A fuel cell
While charging a battery, which one should be strictly followed?
A. Keep it in a well-ventilated room
B. Check the acid level with a lighted match sticks
C. Short circuit the terminals of the battery to see if its already fully charge
D. Connect and disconnect the battery from time to time to rest the supply
The ampere-hour capacity of an industrial battery is based on how many hours of discharged?
A. 12 hours
B. 8 hours
C. 24 hours
D. 6 hours
Which one is an active material of a nickel-iron battery?
A. Nickel hydroxide
B. Powdered iron and its oxide
C. 21% solution of caustic potash (KOH)
D. All of these
A dead storage battery can be revived by .
A. a dose of H2SO4
B. adding so-called battery restorer
C. adding distilled water
D. none of these (it can not be revive)
Which of the following is the best reason why nickel-cadmium cell is commonly used as power supplies to electronic calculators?
A. It is rechargeable
B. It is a dry type cell
C. It is easily manufactured
D. It has a standard shape
The output voltage of a lead-acid cell is .
A. 1.25 V
B. 1.35 V
C. 2.1 V
D. 6 V
What happens if a lead-acid battery was left discharged for a longer time?
A. Its acid will evaporate
B. Its electrolyte will become more weak
C . The electrolyte will eat up the container
D. The plates will become sulphated
For the process of electrolysis, what supply voltage is required?
A. dc supply
B. ac supply
C. dc or ac supply but it should be varying
D. dc or ac supply as long as it is constant
The lead-acid battery should be recharged when the specific gravity of the electrolyte is about .
A. 1.15
B. 1.25
C. 1.35
D. 1.45
When a lead-acid battery is fully charged, what is the color of its positive plate?
A. Black
B. Dark red
C. Dark brown
D. Dark gray
Which one is an active material of a lead-acid cell?
A. Lead peroxide
B. Sponge lead
C. Dilute sulphuric acid
D. All of these
Which of the following is considered a major drawback of a primary cell?
A. Chemical action is not reversible
B. Chemical action is reversible
C. The electrolyte used is expensive
D. It is not portable
What is the function of the depolarizer in a carbon zinc cell?
A . It converts the produced hydrogen into water
B. It absorbs the oxygen produced in the cell
C. It prevents the fast chemical action on the zinc
D. It synthesizes the decomposed electrolytes
Which of the following acts a depolarizer in a dry cell?
A. Carbon poweder
B. Zinc chloride
C. Manganese dioxide
D. Ammonium chloride
A condition called "gassing" occurs in which of the following conditions?
A . Charging an accumulator
B . Charging a dry cell
C. Discharging a dry cell
D. Discharging an accumulator
The life of a lead-acid battery is expected to be.
A . about 2 to 6 months
B. about 1 year
C. about 2 to 5 years
D. about 10 to 15 years
Which of the following is the major drawback of nickel-cadmium cell?
A. It has a short life
B. It is very expensive
C. It has a high internal resistance
D. It takes much time in charging
The best indication about the state of charge on a lead-acid battery is given by .
A. output voltage
B. color of electrolyte
C. temperature of electrolyte
D. specific gravity of electrolyte
As to practice, the life of the positive plate in a lead acid cell is approximately ( ) to that of the positive plate.
A. twice
B. one-half
C. equal
D. one-quarter
In which of the following devices would a transistor battery be the best power choice?
A. An electronic calculator
B. An LCD wall clock
C. A two-way portable radio
D. A heart pacemaker
What is the average voltage of a dry cell?
A. 1.5 V
B. 2.0 V
C. 1.1 V
D. 1.3 V
Which of the following battery is used for aircraft?
A. Lead-acid battery
B. Nickel-iron battery
C. Silver-oxide battery
D. Manganese-alkaline battery
Battery charging equipment is usually installed where?
A . In a well ventilated location
B. In a clean and dry places
C. As near as practical to the battery being charged
D. All of these
A lead-acid cell is being charged. When the specific gravity of the electrolyte is about 1.25, the cell ( ) is percent charged.
A. about 75%
B. about 25%
C. 100%
D. about 50%
Which of the cells is used as voltage reference for instrument calibration?
A. Nickel-cadmium cell
B. Mercury-cadmium cell
C. Solar cell
D. Dry cell
At what condition is the efficiency of a dc generator be maximum?
A . The magnetic losses are equal to the mechanical losses
B. The field copper losses are equal to the constant losses
C. The stray power losses are equal to the constant losses
D. The armature copper losses are equal to the constant losses
The yoke of a dc machine is made from which of the following?
A. Silicon steel
B. Aluminum
C. Soft iron
D. Cast steel
Commutator segments are made from which of the following materials?
A. Hard-drawn copper
B. Manganin
C. Brass
D. Aluminum
Which one is the function of the pole in a dc machine?
A. To support the field coils
B. To spread out the flux
C. To reduce the reluctance of the magnetic path
D. All of these
In a lap winding dc generator, how many brushes are needed?
A. Exactly two brushes
B. Equal to the number of poles
C. Equal to the number pairs of poles
D. Equal to twice the number of poles
In dc machines the mechanical losses are primarily dependent on which of the following?
A. Current delivered
B. Voltage induced
C. Speed
D. Flux density
Which of the following is the excitation current of the series field in a long-shunt compound dc generator?
A. Armature current
B. Shunt field current
C. Load current
D. External current
What is the reason why a separately-excited dc generator is no longer used today?
A. It is an expensive machine
B. The terminal voltage drops considerably with load
C. A separate dc source is required for its field circuit
D. It is only available in low kW rating
A wave winding must go at least how many times around the armature core before it will close back to where it started?
A . Once
B. Twice
C. Thrice
D. Four times
The field windings of a dc shunt machine usually carries what percent of the rated current of the machine?
A. 2% to 5%
B. 10% to 15%
B. More than 20%
D. Less than 1%
Shunt generators are the most suited for stable parallel operation due to which of the following voltage characteristics?
A. Linear
B. Identical
C. Rising
D. Drooping
In dc machines, the armature windings are placed on the rotor because of the necessity for which of the following?
A. Commutation
B. Generation of voltage
C. Development of torque
D. Electro-mechanical energy conversion
What is the reason why, the coil span of a dc armature winding must be equal to the pole pitch?
A. To save the length of the coil used for the windings
B. To distribute the windings uniformly under the different poles
C. To ensure the addition of emfs for consecutive turns
D. To make the machine deliver more current at a definite voltage
What is the terminal voltage of a series generator running at rated speed and at no load?
A. Zero
B. Rated voltage
C. More than its rated voltage
D. A very little voltage
Which of the following dc generator losses varies with the load connected to the generator?
A. Eddy current loss
B. Hysteresis loss
C. Copper loss
D. Friction and windage loss
The ball bearing is secured to the shaft of a dc generator by which of the following?
A. Key
B. Slot
C. Pin
D. Sleeve
Which one is considered the real working part of dc machine?
A. Armature windings
B . Field windings
C. Armature core
D. Commutator & brushes
How much is the commutator pitch for a simplex lap winding?
A. Equal to the pole pitch
B. Equal to twice the pole pitch
C. Equal to 1
D . Equal to half the pole pitch
Which of the following would cause a generator fail to build up?
A. Reversed field connections
B. Speed too low
C. Generator is short-circuited
D. All of these
Which of the following is true about a dc machine having four poles?
A. All four poles are north poles
B. All four poles are south poles
C. Two north poles follow two south poles
D. Alternate poles are north and south
Which type of dc generators is used for arc welding purposes?
A. Series generator
B. Shunt generator
C. Cumulatively compounded generator
D. Differentially compounded generator
With a dc generator which of the following voltage regulation is more preferred?
A. 1%
B. 50%
C. 100%
D. 75%
Which of the following generators is used for charging automobile batteries?
A. Series generators
B. Shunt generators
C. Long shunt compound generators
D. Short shunt compound generators
What is the reason for the rapid brush wear in dc generators?
A. Imperfect contact
B. Severe sparking
C. Rough commutator surface
D. All of these
What do you mean by "flashing" in a dc generator?
A. To increase the flux density by adding more turns in the field poles
B . To create residual magnetism by a dc source
C. To perform a short circuit test in the generator
D. To increase the excitation current in the field by lowering the rheostat resistance
Equalizer connections are required when connecting two or more what type of dc generators?
A. Series generators
B. Shunt generators
C. Compound generators
D. All of these
What will happen if the field resistance of a dc shunt generator is increased beyond its critical value?
A. The generator will not build up
B. The output voltage will exceed the nameplate rating
C. The generator may burn out if loaded to its nameplate rating
D. The power output may exceed its nameplate rating
In dc generators, the wave windings are used in which applications?
A. Low voltage and low current
B. High voltage and high current
C. Low voltage and high current
D. High voltage and low current
What is the reason why dc generators are installe near the load center?
A. To reduce the iron losses
B. To reduce the sparking at the brushes
C. To reduce the corona losses
D. To reduce the line losses
How do you call a compound generator that has a voltage drop from no-load to full load?
A. Under compounded
B. Over compounded
C. Under-flat compounded
D. Flat compounded
What is the probable cause why a dc generator gives electric shock upon touching its body?
A. Weak insulation on the armature coils
B. Loose earth wire
C. Grounded armature coils
D. All of these
What is the proper color of a commutator?
A. Glazed chocolate
B. Dark brown
C. Reddish brown
D. Shiny brown
What is the coupling field between electrical and mechanical systems of a dc machine?
A. Electric field
B. Magnetic field
C. Mechanical field
D. All of these
What is the effect of the armature magnetic field to the main magnetic field?
A. It will demagnetize or weakens the main field
B. It will cross magnetize or distort the main field
C. It will magnetize or strengthen the main field
D. Both A and B
In the commutation process which of the following is getting reversed?
A. Current
B. Voltage
C. Power
D. All of these
Which of the following is a simple method of increasing the voltage of a dc generator?
A. Increase the length of armature
B. Increase the air gap of flux density
C. Increase the load on the generator
D. Increase the speed of rotation
How do you call the armature winding pitch in which the coil sides are a pole pitch apart?
A. Full pitch
B. Fractional pitch
C. Pole pitch
D. Unity pitch
In dc generators, the generated emf is directly proportional to which of the following?
A. Number of armature current paths
B. Field current
C. Pole flux
D. Number of dummy coils in the armature
In a dc shunt generator, maximum efficiency will occur when?
A. The core loss and mechanical losses are equal
B. The copper loss and core loss are equal
C. The friction & windage loss is equal to core loss
D. The constant loss is equal to the variable loss
What is the purpose of placing the armature windings of the dc generator on the rotor?
A. To save the iron
B. To reduce the losses
C. To reduce the armature reaction
D. To facilitate commutation
A 4-pole dc machine has how many magnetic circuits?
A. 2
B. 4
C. 8
D. 0
What is the classification of a dc generator that receives its field excitation from internal source?
A. Self-excited
B. Separately excited
C. Internally excited
D. Under excited
DC generators works on the principle of .
A. Flemmings left hand rule
B. Flemmings right hand rule
C. Lenz' law
D. Joule's law
What is the major effect of the phenomenon called "armature reaction"?
A. It can cause the total flux to decrease
B. It can cause partial short circuit in the armature
C. It can cause the armature core to run wild
D. It can cause big power loss in the armature
What is the main function of the interpoles in a do generator?
A. To minimize friction between brushes and commutator
B. To minimize wear and tear between brushes and commutator
C. To minimize sparking between the brushes and the commutator
D. None of these
Which of the following dc generators are suitable for running in parallel?
A. Series generators
B. Shunt generators
C. Compound generators
D. Any of these
The Flemming's right hand rule correlates which of the following?
A. Magnetic flux, direction of force and direction of motion of conductor
B. Magnetic field strength, induced voltage and current
C. Magnetic flux, direction of motion and the direction of emf induced
D. Magnetic flux, direction of current flow and resultant force
How does an interpole winding be connected in a dc generator?
A. In series with the armature windings
B. In parallel with the field winding
C. In series with the field windings
D. In parallel with the armature windings
An "exciting current" is one that is required in which of the following?
A. To create a magnetic field
B. To charge a battery
C. To excite a synchronous motor
D. To build up a dead circuit
When cleaning a commutator which of the following is never used?
A. Sandpaper
B. Clean cloth
C. Emery
D. Both A and B
In a dc machine, which one is a bigger loss in comparison to other losses?
A. Stray power loss
B. Copper loss
C. Mechanical loss
D. Eddy current loss
Which of the following will cause generator brushes to burn?
A. Brushes not in neutral plane
B. Generator overloaded
C. Weak brush springs
D. All of these
Which generators would you prefer for feeding long dc transmission lines?
A. Series generator
B. Shunt generator
C . Flat compounded generator
D. Over-compounded generator
Which one describes the voltage build up process of a dc generator?
A. It is cumulative
B. It is delayed
C. It is infinite
D. It is difficult
Which of the following losses occurs in the yoke of a dc generator?
A. Iron loss
B. Copper loss
C. Heat loss
D. No losses
In a dc generator, the generated emf is dependent on which of the following?
A. Flux only
B. Speed only
C. Both flux and speed
D. Neither flux nor speed
What is the purpose of laminating the armature core in a dc generator?
A. Reduce the eddy current loss
B. Insulate the core from overheating
C. Provide passage for cooling air
D. Reduce the weight of the core
How do you call a dc compound generator whose full-load terminal voltage is equal to the no-load terminal voltage?
A. Under-compounded
B. Flat-compounded
C. Cumulative-compounded
D. Over-compounded
What is the usage of the instrument called "growler" in a generator?
A. It is used to check the shorted and open coils in the generator windings
B. It is used to check the alignment of the shaft between the generator and prime mover
C. It is used to check the conditions of the insulation in the generator windings
D. It is used to check the lubrications of the bearings of the generator
Grooves around the circumference of a commutator indicates which of the following?
A. High mica
B. Improper brushes
C. Open armature circuit
D. Improper brush staggering
What is the purpose of staggering brushes?
A. To even out the load
B. To reduce chattering
C. To prevent the uneven wear on the commutator
D. To cover more area on the commutator segments
Equalizer rings are necessary in dc machines if the the armature is using what type of windings?
A. Wave wound
B. Lap wound
C. Duplex wound
D. Simplex wound
What type of bearing is used to support the rotor shaft in a dc generator?
A. Magnetic bearings
B. Bush bearings
C. Neddle bearings
D. Ball bearings
Brushes in dc generators are made from which of the following?
A. Carbon
B. Mica
C. Bronze
D. Copper
Residual magnetism is necessary is which type generators?
A. Separately-excited generators
B. Self-excited generators
C. High voltage alternators
D. Low voltage generators
What losses are sometimes called "stray losses?
A . Copper and iron losses
B. Armature and field winding losses
C. Iron and mechanical losses
D. Excitation and rheostat losses
Which of the following dc generators cannot build up on open circuit?
A. Shunt generator
B. Series generator
C. Short shunt compound generator
D. Long shunt compound generator
The ball bearings used in dc generators are made from which of the following materials?
A. Carbon chrome steel
B. Silicon steel
C. Cast iron
D. Mild steel
A belt driven cumulative compounded dc generator is delivering power to the dc mains. If the belt snaps, which one will likely to happen?
A. The machine will run as a cumulative compound motor running in the same direction
B. The machine will run as a cumulative compound motor running in the opposite direction
C. The machine will run as a differential compound motor running in the opposite direction
D. The machine will run as a differential compound motor running in the same direction
A dc generator has been exposed to water. Which of the following instruments would be used to determine if its safe to operate?
A. A megger
B. A voltmeter
C. A hydrometer
D. A tachometer
DC generator voltage is increased by which of the following?
A. By cutting-in field resistance
B. By cutting-out field resistance
C. By cutting-in armature resistance
D. By cutting-out armature resistance
What is the material generally used for commutator brushes?
A. Mica
B. Copper
C. Cast iron
D. Carbon
In a dc generator, the number of commutator segments is equal to which of the following?
A. Number of turns
B. Number of coils
C. Number of slots
D. Number of coil sides
What is the purpose of using compensating windings in dc generators?
A . To neutralize the armature reaction
B. To reduce the eddy current loss
C. To provide path for circulating air
D . To decrease the reluctance of the magnetic path
What is the voltage regulation of an overcompounded dc generator?
A. Positive
B. Negative
C. Almost zero
D. Very high
Which of the following is used to connect the commutator segments to the armature conductors?
A. By brazing
B. By copper lugs
C. By insulation pads
D. By resistance wires
Which dc generators has the poorest voltage regulation?
A. Series generator
B. Shunt generator
C. Long shunt compound generator
D. Short shunt compound generator
Which of the following would cause sparking at the brushes in a dc generator?
A. High mica
B. Dirty commutator
C. Grooved commutator
D. All of these
Which of the following is an essential requirement for stable parallel operation of dc generators?
A. Same percentage regulation
B. Drooping voltage characteristics
C. Same kW output ratings
D. Same no-load to full load speeds
The iron losses in a dc machine are independent of which of the following variations?
A. Voltage
B. Load
C. Speed
D. All of these
How do you call a compound generator that has a voltage rise from no-load to full load?
A. Flat compounded
B. Under compounded
C. Over compounded
D. Under-flat compounded
What is the output of a single loop dc generator?
A. Steady ac
B. Steady dc
C. Pulsating ac
D. Pulsating dc
In a dc machine, the biggest eddy current loss occurs where?
A. Field poles
B. Yoke
C. Armature core
D. Commutating poles
Which of the following load characteristics is a good application of a shunt generator?
A. Constant voltage over a wide range of load
B. Constant voltage over a narrow range of load
C. Constant current over a wide range of load
D. Constant current over a narrow range of load
How can the ripples of output voltage in a dc generator be reduced?
A. Use commutator with more segments
B. Use bigger size of armature conductors
C. Use more brushes
D. Use equalizer rings
The current in the armature conductors of a dc generator is what type?
A. Pulsating dc
B. ac
C. Pure dc
D. Combination of dc and ac
How does a compensating winding be connected in a dc generator?
A. In series with the field windings
B. In parallel with the field windings
C. In parallel with the armature windings
D. In series with the armature windings
What is the purpose of a commutator in a dc 'generator?
A. To rectify the armature current
B. To keep a constant voltage output
C. To minimize armature reactions
D. All of these
What is the insulating medium used between commutator segments?
A. Mica
B. Graphite
C. Paper
D. Varnish
How much is the commutator pitch for a simplex wave winding?
A. Equal to 1
B. Equal to the pole pitch
C. Equal to half the pole pitch
D. Equal to twice the pole pitch
Which of the following would cause one bar of a commutator segment to blacken?
A . A shorted coil
B. An open coil
C. A grounded coil
D. All of these D. All of these
How many parallel paths are there if the armature winding is simplex wave winding?
A. Two paths
B. Only one path
C. Equal to the number of poles
D. Equal to half the number of poles
Which of the following type of brushes has the least voltage drop?
A. Graphite brush
B. Carbon brush
C. Cast iron brush
D. Metal graphite brush
What is the emf induced in a conductor rotating in a bipolar field?
A. DC
B. AC
C. Both DC and AC
D. None of these
High mica between commutator bars is removed by which of the following?
A. Hot air blowing
B. Chiseling
C. Undercutting
D. Wiping with a clean cloth
How do you call the resistance of the windings of a generator?
A. Internal resistance
B. Induced resistance
C. Critical resistance
D. Terminal resistance
What is the simplest way to shift load from one dc shunt generator running in parallel with another?
A. Use equalizer connections
B. Adjust their field rheostat
C. Insert resistance in their armature circuit
D. Adjust the speed of their prime movers
What is the primary purpose of a commutator in a dc generator?
A. To increase the output voltage
B. To reduce sparking at the brushes
C. To provide smoother output voltage
D. To convert the ac induced voltage to dc
In dc generators, the lap windings are used in which applications?
A. Low voltage and high current
B. High voltage and low current
C. Low voltage and low current
D. High voltage and high current
What is the primary reason for providing compensating windings in a dc generator?
A. To compensate for decrease in main flux
B. To neutralize the armature mmf
C. Maintain uniform flux distribution
D. Neutralize cross-magnetizing flux
The field coils of a dc generator are usually made from which of the following?
A. Copper
B. Mica
C. Cast iron
D. Silicon steel
What is the voltage regulation of an ideal dc generator?
A. Positive value
B. Zero
C. Negative value
D. Very high value
In dc shunt generator which one is called constant loss?
A. Iron and field circuit losses
B. Iron and mechanical losses
C. Friction, windage and stray load losses
D. Friction, windage iron and field circuit losses
Which of the following will restrict the voltage build up in a shunt generator?
A. Saturation of iron
B. Speed of the prime mover
C. Armature core heating
D. Number of armature coils
The term "critical resistance"refers to which of the following resistances?
A. Armature resistance
B. Diverter resistance
C. Brush contact resistance
D. Field resistance
What is the purpose of having an equalizer bar when connecting two compound generators in parallel?
A. To make the operation stable
B. To make the operation regular
C. To make the operation possible
D. To make the operation smooth
Which of the following dc generators will have a terminal voltage that varies widely with changes in load current?
A. Shunt generator
B. Series generator
C. Long shunt compound generator
D. Short shunt compound generator
Which of the following is the excitation current of the series field in a short-shunt compound dc generator?
A. Armature current
B. Shunt field current
C. Load current
D. External current
The external characteristics of a dc shunt generator can be obtained directly from which of the following characteristics?
A. Internal characteristics
B. Load-saturation characteristics
C. Performance characteristics
D. Open-circuit characteristics
How would you determine, from visual inspection that the armature winding is lap or wave connection?
A. Its connection to the field windings
B. Its connection to the brushes
C. Its direction of the end connection
D. Through the number of commutator segments
According the Flemmings right hand rule for finding the direction of the induced emf, the forefinger points the direction of which of the following?
A. Motion of conductor
B. Lines of force
C. Current
D. Power
Which one is true about the comparison between a dc machine and an ac machine with the same rating?
A. The dc machine has more weight
B. Both machines have similar weight
C. The dc machine has lesser weight
D. Either A or C, but seldom on B
Which of the following component of a dc generator plays an important role for providing direct current?
A. Field windings
B. Equalizer rings
C. Commutator
D. Types of armature windings
The yoke of a dc machine carries what percentage of the total total flux?
A. 100%
B. 50%
C. 25%
D. zero or no flux
If a self-excited dc generator fails to build up on its first trial after being installed, what will you do?
A. Reverse the field connection
B. Increase the field resistance
C. Increase the speed of the prime mover
D. Check the armature resistance
Which of the following dc generators will build up without any residual magnetism?
A. Series generator
B. Shunt generator
C. Compound generator
D. Separately-excited generator
How many parallel paths are there in a simplex lap windings?
A. Equal to the number of poles
B. Equal to the number of pairs of poles
C. Equal to twice the number of poles
D. Only two, independent on the number of poles
In dc generators, the armature reaction is produced by which of the following?
A. Its field current
B. Its armature conductors
C. Field pole windings
D. Load current in the armature
Which of the following windings are used in a dc welding generator?
A. Lap windings
B. Wave windings
C. Duplex wave winding
D. Drum windings
The armature of dc machine is made from which of the following materials?
A. Silicon steel
B. Cast steel
C. Wrought iron
D. Soft iron.
In dc generators, the pole shoes are fastened to the pole cores using which of the following?
A. Rivets
B. Brazing
C. Welding
D. Counter sunk screws
High voltage dc generators uses what type of windings?
A. Lap
B. Wave
C. Either lap or wave
D. Combination of lap and wave
What is the purpose of having a dummy coil in a d generator?
A. To reduce the copper loss
B. To generate more voltage
C. To distribute the armature current
D. To provide mechanical balance for the rotor
If the shunt field of a compound generator is connected across both the series field and armature windings, how do you call the generator?
A. Short shunt compound generator
B. Long shunt compound generator
C. Cumulative compound generator
D. Differential compound generator
In electrical machines which of the following materials are used in the pole shoes of the electromagnets?
A. Pure iron
B. Aluminum
C. Copper
D. Cast steel
Which one is true about the polarity of the interpoles in a dc generator?
A. The same as that of the main poles ahead
B. Opposite to that of the main pole ahead
C. It has no polarity since it does not play an important role in generating an emf
D. Either north or south depending on number of interpoles
How can the residual magnetism of a dc shunt generator be restored assuming it is accidentally destroyed?
A. Ground the shunt field
B. Connect the shunt field to an ac source
C. Connect the shunt field to a dc source
D. Reverse the connection of the shunt field
For the same rating, which dc motor has the lowest starting torque?
A. Shunt motors
B. Series motors
C. Long-shunt compound motors
D. Short-shunt compound motors
The shaft torque of dc motor is less than the armature torque due to this loss. Which one?
A. Copper loss
B. Iron loss
C. Mechanical loss
D. Rotational loss
Which of the following is the most common method used in controlling the speed of a dc motor?
A. Vary the supply voltage
B. Vary the field strength
C. Vary the number of field poles
D. Vary the armature circuit resistance
What is the rotating part of a dc motor?
A. Pole
B. Stator
C. Armature
D. Carbon brush
A cumulative compound motor is best to be used in which of the following requirements?
A. Variable speed
B. Constant speed
C. High speed but low torque
D. Sudden heavy loads for short duration
What is the reason why a series dc motor is always started with a mechanical load?
A. The motor will not run if started without a load
B. The motor will run at very high speed if started without a load and damage itself
C. The motor draws low current making its speed to become very low if started without a load
D. The motor will act as a generator if started without a load
Which of the following basically determines the speed of a dc series motor?
A. Field excitation
B. Armature resistance
C. Supply voltage
D. Load carried
Which of the following is used to determine the direction of rotation in a dc motor?
A. Flemming's left hand rule
B. Faraday's law
C. Lenz' law
D. Flemming's right hand rule
Which one is true about the speed of a dc motor?
A. It is directly proportional to the flux per pole
B. It is inversely proportional to the flux per pole
C. It is directly proportional to the square of the flux per pole
D. It is inversely proportional to the square of the flux per pole
What will happen if the field of a shunt motor is suddenly open circuited?
A. The motor will quickly stop from running
B. The speed of the motor will decrease a little
C. The speed of the motor will become so high
D. The motor will continue to run at same speed
In starting a differential compound dc motor, the series field winding must be short circuited first. Why?
A. To prevent the circuit breaker to trip due to large starting current
B. To prevent the motor from starting in the wrong direction
C. To prevent the motor to start at high speed
D. To reduce the losses of the motor at starting
Which one is a common cause why dc motors will overheat?
A. Overloads
B. Over voltage supply
C. Loose parts
D. Rough commutator segments
An electric train employing a dc series motor is running at a fixed speed when a sudden slight drop in the supply voltage. What will happen?
A. Speed will decrease and current will increase
B. Speed will increase and current will decrease
C. Both speed and current will increase
D. Speed will decrease but the current will remain the same
Why is the air gap between field poles and armature core of a dc motor be kept as small as possible?
A. To decrease the eddy current loss
B. To get a stronger magnetic field
C. To improve the air circulation in the core
D. To achieve a stable speed
As compared to shunt and compound motors, the series motor has the highest starting torque for which of thee following reasons?
A. It has a stronger field at start
B. It has fewer series turns at start
C. It has a larger armature current at start
D. It has a lower armature current at start
In a dc motor where is the power output of the machine collected?
A. Commutator through the brushes
B. Armature conductors through slip rings
C. Coupling mounted on the shaft
D. Through the motor terminals
What is the back emf of the motor when the mechanical power developed by a dc motor is maximum?
A. Equal to zero
B. Equal to the applied voltage
C. Equal to half the applied voltage
D. It is approaching the value of the applied voltage
DC shunt motor speed is increased by which of the following?
A. Shifting brushes
B. By cutting-in rheostat resistance in the shunt field
C. By cutting-out rheostat resistance in the shunt field resistance
D. None of these
Which one is true about the speed of a dc motor?
A. It is directly proportional to back emf and inversely proportional to flux
B. It is directly proportional to flux and inversely proportional to back emf
C. It is directly proportional to both back emf and flux
D. It is inversely proportional to both back emf and flux
If a motor frame is found to be excessively hot, which of the following is not likely the cause?
A. Excessive loading
B. Inadequate internal ventilation
C. Very high ambient temperature
D. Faulty starter
What will you do if the speed of a dc shunt motor should be increase mere than the full load speed?
A. Increase the armature current
B. Increase the field current
C. Decrease the field current
D. Decrease the armature current
