MTA Transit Electrical Helper (Exam No. 4612) Practice Exam

These questions are part of the practice quiz. Start practicing

• What does a short-circuited condenser indicate in an electrical circuit?
• A condenser with a safe working voltage of 250 volts DC is most likely to break down if used across which type of line?
• What happens if a condenser rated for a safe working voltage of 250 volts DC is used across a 250 volt 60 cycle AC line?
• An air conditioning unit rated at 1000 watts operates for ten hours per day. What is the weekly electricity cost if the rate is five cents per kilowatt hour?
• What is a milliampere equivalent to in amperes?
• What is the primary function of an alternator?
• What effect does decreasing the length of a wire conductor have on its resistance?
• What is the most important reason for not having a power line splice in a conduit run between boxes?
• How many ordinary flashlight cells are needed to obtain 6 volts when connected together?
• What is the best material for an electric contact finger subject to constant bending?
• What type of maintenance would most effectively prevent corrosion in electrical connections?
• What is the first step in resetting the transfer switch to the normal side?
• If a scale on a shop drawing is 1/4 inch to the foot, what is the actual length of a part that measures 3 3/8 inches long on the drawing?
• Which device is commonly used to smooth out the ripples present in rectified AC?
• How many fuses are required in a three-phase four wire branch circuit with ground and neutral?
• A circular mil is a unit of measurement for what?
• If one insulated rail joint becomes short-circuited, how many track signal circuits will be affected?
• Using transformer laminations primarily addresses which issue?
• The letters "t" and "v" are used together in a circuit to achieve what purpose?
• What symbol is used to represent a capacitor in electrical diagrams?
• Which tool is considered proper for making a hole through a transit panel?
• In lifting heavy objects, what body mechanics are recommended?
• The lead sheath of a cable is primarily for protecting the cable from what type of damage?
• A rheostat is least likely to be used in connection with the operation of?
• What is the primary function of a motor controller?
• To accurately measure the small gap between relay contacts, which tool is the most suitable?
• An electrician's hickey is primarily used for what purpose?
• In an electrical circuit, what causes arcing across the contacts of a panel board switch when it is opened?
• Which is a primary task performed by a mega instrument?
• What type of solder should be used when soldering two #20 AWG copper wires together?
• Which type of circuit is responsible for power delivery in a shunt generator?
• What instrument should be used to measure the state of charge of a lead acid storage battery?
• A worker merely wearing a helmet while handling overhead installations is primarily protected from?
• Where is it recommended to connect the ground wire for a building electrical system?
• The rating term "20 watts 500 ohm" would generally be applied to which component?
• What is a significant risk when soldering electronic components like transistors?
• The circuit shown contains which type of rectifier?
• In subway systems, what is the primary purpose of connecting heavy copper bonds across the joints of track rails?
• The specification 6-32 for a machine screw refers to the diameter and what other characteristic?
• Which instrument is proper for determining the diameter of the conductor of electric hookup wire?
• What is a potential consequence of an ungrounded electrical system?
• What safety precaution should be taken when working with electrical circuits?
• What type of gears are used to transmit mechanical power between two shafts at right angles to each other?
• To vary the speed of a DC motor generator set, which component is necessary?
• To measure a voltage higher than the maximum scale of a DC voltmeter, one should use?
• In a polarized electric cord plug, how are the contact blades oriented?
• To measure the amount of electrical power used in a balanced three-phase circuit, which instrument should you use?
• What device is indicated by the letter "s"?
• Which type of battery is primarily discussed in the context of guarding against sparks?
• Which AWG size of single conductor bare copper wire has the lowest resistance per foot?
• What is the main implication of static electricity accumulation in windings before electrical testing?
• What occurs if wires encounter damage during the installation of a conduit with multiple bends?
• A commutator and brushes are typically found in which type of device?
• What is powdered graphite commonly used as?
• What is the purpose of connecting a condenser across contact points in a DC circuit?
• What is the sum of the lengths 6'6", 5'9", and 2'1 1/2"?
• What is a notable advantage of mercury arc rectifiers over rotary converters?
• Which metal is preferred for use in relay contacts?
• What is considered the poorest conductor of electricity?
• What is the effect of increasing the resistance in a circuit on current flow, according to Ohm's law?
• What is the current drawn by a 10 ohm resistor with 120 volts applied?
• What type of lamp is used for providing heat in electrical applications?
• Which type of voltmeter is specifically designed to measure electrostatic voltage?
• Which of the following is NOT a benefit of using photoelectric cells?
• To reduce the pitting of relay contacts that make and break frequently, what unit is generally connected across them?
• What instrument is used to determine whether 25 Hz or 60 Hz is present in an electrical circuit?
• How many conductors are required to connect a three-phase delta connected heater bank to an electric power panel board?
• If one side of a fuse clip is harder than the other, what does this indicate?
• Which of the following materials is the best conductor of electricity?
• What is the effect of connecting two different capacitors in series on the total capacitance?
• Through which component do the signal mains receive their power?
• What is a limitation of an auto transformer?
• What is the primary function of a switch in electrical circuits?
• How is the size of a screwdriver typically defined?
• If a bathroom heating unit draws 10 amperes at 115 volts, what should be the hot resistance of the heating unit?
• What is the full load current for a 5 ohm, 20 watt resistor?
• Which switches need to be closed to light the 300 W lamp?
• Why is aluminum often used for transmission lines instead of copper?
• In a situation where minor injuries occur, what is essential knowledge for employees to possess?
• Which instrument is best to measure a small gap between relay contacts?
• Why are transit workers cautioned not to leave tools on scaffolding?
• What is the unit of measurement for electrical resistance?
• What is the main purpose of the oil in an oil circuit breaker?
• What is the approximate voltage output of six ordinary flashlight dry cells when connected in parallel?
• Which of the following is typically used for grounding in electrical systems?
• What is the primary function of an outlet box in electrical installations?
• What is the primary function of the signal main in a transit system?
• Why is it important for metal cabinets housing electrical equipment to be grounded?
• What happens if pressure is not removed from the hoseline before opening an automatic hose connection?
• What will happen if a 120 volt transformer is connected to a 120 volt DC source?
• Which metal is considered the best conductor of electricity?
• Which electrical device is not normally used in direct current circuits?
• What is an important reason not to place telephone wires in the same conduit as AC power lines?
• How is rigid conduit attached inside a junction box?
• What should a screwdriver's blade look like to be considered in good condition?
• Which resistor in a series circuit will consume the most power?
• The transfer switch is held in the emergency supply position by what component?
• What is the common capacity rating unit for most filler capacitors found in radios?
• What type of current does a filter device primarily work on?
• Under what condition may electrical outlet boxes not require drilling for conduit entrance?
• To measure the frequency of an electrical signal, the appropriate tool would be a?
• A non-inductive carbon resistor consumes 50 Watts when connected across a 120 volt DC source. What is the power consumed when connected across a 120 volt AC source?
• In long conduit runs, pole boxes are installed at intermediate points to?
• Why is it prohibited for electrical maintainers to allow the replacement of lamps with higher wattage in their work areas?
• A thermal couple is used primarily for what purpose?
• To operate a 6 volt lamp from a 120 volt AC source with minimal waste power, which device is used?
• Which material is found in an ordinary telephone transmitter?
• What is the primary reason for using circuit breakers in electrical systems?
• What does a ground fault circuit interrupter (GFCI) do?
• If five identical electric fans rated at 120 volts DC are connected in series on a 600 volt circuit and one fan develops an open circuit, what will happen?
• What is the common reason for the rapid deterioration of rubber insulation?
• What is the purpose of a thermocouple?
• For measuring the width of a door, what is the proper instrument to use?
• What is the best immediate first aid treatment for a scraped knee?
• Which material is considered a good magnetic material?
• If a wire has a resistance of two ohms per 1,000 ft, what will be the resistance of a 1,500 ft long piece of this wire?
• When is it most critical to slow down your cutting speed when using a hacksaw?
• Light bonds are provided on the rail joints of what type of rails?
• Which tool is recommended for cutting BX wiring?
• What is the approximate voltage on the signal main?
• In protection circuits, what is the main function of relays?
• Which combination of lamps will draw the most current from a standard 120 volt branch circuit?
• Which material is considered a good magnetic material?
• Why is twisted pair wire desirable for telephone use?
• What type of wire is portable lamp cord most likely to have?
• How are track signal circuits separated from others?
• Before opening an automatic hose connection, why is it important to remove pressure from the hoseline?
• Why is conduit galvanized?
• A capacity rating expressed in ampere hours is commonly associated with what type of device?
• What tool is best for accurately tightening a bolt to twenty-eight foot-pounds?
• What is a potential consequence of overheating a soldering iron?
• Why is it important for a newly appointed helper to follow the prescribed methods in their work?
• If the load on the secondary of a small 10 to 1 step-up transformer is 100 watts, what is the power being drawn from the power line by the primary?
• What is the maximum fuse size that should be used for a two-wire lighting circuit when using number 14 wire?
• What is the purpose of a one-to-one transformer?
• To measure the insulation resistance of a rubber covered electrical cable, which instrument is appropriate?
• When a solid splice is covered with rubber and friction tape, what is the main function of the friction tape?
• What properties make squirrel cage induction motors different from others?
• What material is the core of an electromagnet usually made of?
• Why are blue lights used to indicate the locations of telephones alongside subway tracks?
• What is the function of a step down transformer?
• Why is it important for a new helper to consider advice from an experienced helper?
• What is a critical reason for quickly replacing broken colored lenses on subway signals?
• What material is commonly used for brushes on DC motors?
• In electrical work, what do the metal frames of units serve to enhance?
• If a 10-watt lamp and a 100-watt lamp, each rated at 120 volts, are connected in series to a 240-volt source, what will the voltage across the 10-watt lamp be?
• What does it indicate when emergency power is feeding the signal mains?
• Which component is essential for measuring electrical current in a circuit?
• What is the primary purpose of lock nuts in electrical connections on Terminal boards?
• What is the sum of 0.365 + 3.941 + 10.676 + 0.784?
• What precaution should be taken during electric welding?
• What tool is commonly used to assist in pulling wires through conduit?
• What is the correct tool to use when bending a two-inch diameter conduit?
• What is the most logical step to provide Transit employees with quick assistance in the case of minor injuries?
• Which of the following is used to quench electrical arcs in circuit breakers?
• Which material is recognized as a good magnetic material?
• A conduit run is most often terminated in what?
• What is the main reason for wearing safety gear while performing electric welding?
• Which material is typically used for the core of an electromagnet?
• What happens to the voltage in a series circuit if one component fails?
• Which device is most suitable for evaluating the insulation resistance of a conductor?
• What is the best tool to cut off a piece of #0000 insulated copper cable?
• If three 6 volt batteries are connected in parallel, what will be the resultant voltage?
• What is the approved method for protecting wires in a bx type cable from cut ends of the armor sheath?
• When checking the voltage at an AC motor's terminals, which instrument should be used?
• Which material is considered unsuitable as an electrical insulator?
• What is a potential risk associated with handling the material discharged by a carbon dioxide fire extinguisher?
• What is the significance of using specific colors for signal indicators in subway systems?
• Which instrument is used to accurately measure the resistance of a 4700 ohm resistor?
• As compared to a solid conductor of the same diameter, a stranded conductor has what advantage?
• How many 120-volt light bulbs should be connected in series across a 600-volt electric line?
• A tachometer is primarily used for measuring what?
• What is NOT a common size for galvanized sheet metal electrical outlet boxes?
• What happens to the resistance of a wire if its cross-sectional area is increased?
• What is an important consideration when selecting wire coverings?
• What type of circuit allows for multiple current paths but only requires one path to be completed for current to flow?
• When mounting an electrical panel box on a concrete wall, which connectors are best to use?
• In a house bell circuit, where is the push button for ringing the bell usually connected?
• What type of batteries typically have a capacity rating measured in ampere hours?
• What is the common return path for car motors?
• What characteristic makes iron a preferred core material for electromagnets?
• For a 600-volt electric line, what is the maximum recommended number of series-connected bulbs?
• Why are copper tips preferred for soldering irons?
• What device is commonly indicated by the letter R in electrical diagrams?
• If three resistors of 12 ohms, 5 ohms, and 1 ohm are connected in parallel, what will be the combined resistance?
• When specified as 1/4-28, what does the 1/4 indicate?
• In electrical systems, what role does a 'knife switch' primarily serve?
• What type of voltage will be applied to the bell when closing switch "x"?
• When calculating total length in electrical work, which measurement unit is primarily used?
• What is the typical electrical wire size used for telephone circuits?
• What is the total length of electrical conduit required if the lengths are 14'6", 21'3", 6'0", and 22'9"?
• What is the electrolyte used in a lead storage battery?
• Why are pull boxes necessary when installing conduit with multiple right angled bends?
• What is the main purpose of grounding the windings before conducting an insulation resistance test?
• What type of motor can only operate from an AC power source?
• What do steel helmets primarily protect workers from?
• In a transit system, what is typically the highest voltage present?
• When is it least necessary to wear goggles?
• What type of conductors are used in the two wire number 12 armored cable typically used in an ordinary lighting circuit?
• If the needle of a DC voltmeter moves backwards when connections are changed, what does this indicate?
• What is the main purpose of the oil in an oil circuit breaker?
• What type of screwdriver is especially designed for turning screws that are inaccessible to a longer screwdriver?
• What are the electrodes of the common dry cell?
• To properly ground electrical service equipment in a building, a ground connection should be made to which of the following?
• A bank of five 120 volt lamps connected in series is best utilized in checking what type of circuit?
• Which of the following statements is true about an electrostatic voltmeter?
• What type of injury can result from frostbite due to CO2 discharge?
• In an AC circuit that only contains resistance, what will the power factor be?
• What is a good practice when working with standard electrician supplies?
• What instrument is best used to accurately check the diameter of a hole with a tolerance of plus or minus 3000ths?
• In which type of circuit would a power factor meter be used?
• Why is copper preferred in the construction of large knife switches?
• What is the purpose of the reset button on a transfer switch?
• What is the primary role of insulation in electrical wiring?
• What does the voltage on the signal main primarily represent?
• What is a proper use for an electrician's knife?
• The dielectric strength of oil in an oil-filled transformer is a direct measure of what?
• What should a new employee do if they do not understand instructions given by a foreman?
• What is the resistance of a 200 ft long wire if it has a resistance of one ohm per 1000 ft?
• Why is it useful to measure the air gap clearance in a motor?
• Which instrument would be used to accurately gauge the resistance of a wire?
• Which type of motor is most likely to reach a dangerous speed when operated at normal voltage and no load?
• What is the voltage on the contact shoes of the car?
• Rubber insulation deteriorates most rapidly when in contact with which substance?
• What advantage does a 15 ampere circuit breaker have over a 15 ampere plug fuse?
• What happens in an electrical circuit if there is a short circuit?
• What is the purpose of thermal relays in motor circuits?
• How long does one cycle take in a 60 cycle current?
• What is the best procedure for storing tools that are subject to rusting?
• Which wiring material is best known for its high conductivity?
• What important function does a bushing serve on a conduit running into a panel box?
• From a management perspective, what is the most desirable characteristic of a newly appointed helper?
• What is the purpose of taking a voltage drop measurement across a track rail joint in subway systems?
• What is the purpose of a star drill?
• Which of the following is a common use for infrared lamps?
• Why is conduit reamed primarily?
• What is the role of a bushing in cable installations?
• What do the abbreviations ID and OD refer to when describing conduit?
• What is the insulation generally used between commutator bars on a DC motor?
• In what situation would using a retaining circuit be most appropriate?
• Which type of electrical equipment does not require a magnetic field for its operation?
• Why are the metal frames of some electrical units grounded?
• The AWG size is used for specifying what electrical component?
• What happens to an incandescent lamp if it is operated at a voltage below its rated voltage?
• When does a transfer switch automatically connect the signal mains to emergency power?
• How is the pressure of a carbon brush on a commutator measured?
• What is the maximum total voltage that can be measured using two identical 0-300 Volt range DC meters connected in series?
• What should you do if you notice a maintainer about to violate a basic safety rule?
• In terms of electrical wire sizing, what does AWG stand for?
• What is the typical source of power supplied to a Mercury Arc rectifier?
• When two 25 watt, 120 volt lamps are connected in parallel to a 120 volt source, what is the total power consumed by the lamps?
• When using a hacksaw, what is considered good practice regarding cutting speed?
• What is a primary function of electrical conduits in installations?
• If three 1 1/2 volt dry cell batteries are wired in series, what is the total voltage provided by the batteries?
• Of the listed materials, which is the poorest conductor of electricity?
• What is the current drawn by a lamp rated at 300 watts and 120 volts?
• Why are metal cabinets for lighting circuits grounded?
• What is the primary use of series resistance in electrical circuits?
• Before working on a motor to prevent accidental starting, what should you do?
• When testing an electrical circuit for current flow, which instrument would be most appropriate?
• When cutting 0.045 inch thick sheet metal, what is the best hacksaw blade specification to use?
• What is a common issue experienced with DC motors that is related to mica?
• The rating term "20 watts 500 ohm" is generally applied to which component?
• Which tool should be used to pull wire through a conduit when installing electrical circuits?
• What electrical component is commonly used to prevent voltage spikes in a circuit?
• Which instrument allows you to observe the electrical waveform at a point in a circuit?
• The AWG size is used in specifying which electrical components?
• In connection with electrical work, what is good practice to assume?
• Which type of electrical circuit allows current to flow in two or more paths?
• What is a common consequence of arcing at contact points in a DC circuit?
• If a flashlight battery, a condenser, and a flashlight bulb are connected in series, and the bulb burns brightly and steadily, then the condenser is?
• What is the minimum number of 10-ohm, one-ampere resistors needed to achieve an equivalent resistance of 10 ohms capable of carrying a two-ampere load?
• Which type of motor does not have any brushes?
• What voltage type should never be used to charge a storage battery?
• The electrical insulation characteristics of a material largely govern its?
• What electrical characteristic does copper have compared to other materials?
• What effect does operating an incandescent bulb at lower voltage have on its lifespan?
• A kilowatt of power will be drawn from a 500 volt DC supply by a load of?
• Asbestos is mainly used as a covering for wires to protect against what?
• The choice of wiring material can affect which of the following attributes in an electrical system?
• Which tool would you use to ensure a secure connection when joining metal wires?
• In electrical testing, a megohmmeter is calibrated to read which unit of measurement?
• What does a watt meter directly measure?
• What measuring device uses a galvanometer to measure resistance?
• When soldering a transistor into a circuit, what is crucial to protect the transistor from?
• What is the purpose of using a step up transformer?
• What happens to the relay contacts if they become pitted frequently?
• What is the consequence of sediment accumulation in the shells of a storage battery?
• The voltage applied to the terminals of a storage battery for charging cannot be?
• How many threads per inch does a bolt designated as 1/4-28 have?
• Where is the zero adjusting screw typically found?
• What does the term "corrosion" refer to in electrical applications?
• What should be avoided during the maintenance of acid storage batteries?
• What is the risk associated with improperly insulated electrical connections?
• A voltmeter is typically connected to a high potential AC bus through what device?
• What instrument would you use for checking the resistance of a circuit?
• What does the abbreviation DPDT, commonly used in electrical work, refer to?
• What is the main function of a commutator in a shunt generator?
• Which device typically provides a way to connect multiple electrical circuits?
• If switches W, X, Y, and Z are closed suddenly, what will occur?
• What type of current is managed by an auto transformer?
• What is the primary reason for keeping the oil in a transformer tank moisture-free?
• If a blown fuse in an existing lighting circuit is replaced by another of the same rating which also blows, what is the proper maintenance procedure?
• Which type of circuit connection allows for the highest total resistance?
• Which motor can operate only on alternating current?
• A DC device taking 1 milliampere at 1 KV takes a total power of what?
• What is the total gross pay for an employee who works 43 hours in a week at a rate of $10.68 per hour?
• Micah is commonly used as insulation between which components?
• When two unequal condensers are connected in parallel, what happens to the total capacity?
• Which of the following tools is commonly used for measuring electrical current?
• What does a rheostat control in the field circuit of a shunt generator?
• Four resistors with current ratings of 1, 2, 3, and 4 amperes are connected in series. What is the maximum current permissible in this circuit to prevent overload?
• The resistance of heating elements is important for maintaining which electrical property?
• How many ohms are in a Megohm?
• How many conductors are there in a signal main?
• When working with acid storage batteries, what precaution should be observed to prevent accidents?
• For what application is nichrome wire most suitable?
• If the two supply wires to a DC series motor are reversed, what will happen to the motor's direction?
• What component is crucial for controlling the voltage in a generator?
• What kind of protective equipment is essential when working on live electrical circuits?
• Which statement is incorrect regarding an auto transformer?
• What is a key characteristic of a mercury arc rectifier?
• What is the most practical way to determine the approximate length of insulated wire in a large coil?
• A 120 volt AC generator has a full load rating of 12 KVA. What is the full load current for this machine?
• What is the function of a megohmmeter in electrical testing?
• Why is silver used for relay contacts?
• Why is acid not a desirable flux to use in soldering small connections?
• What is used to connect lengths of rigid conduit together to create a long run?
• How many connection points does a 2-pole double throw knife switch have?
• What is one result of corrosion on an electrical connection?
• What is the primary function of a resistor in an electrical circuit?
• Which material is best known for withstanding high temperatures?
• The main purpose of using thin steel laminations in transformer cars is to?
• What is one benefit of properly grounding electrical equipment?
• What is a main disadvantage of using porcelain as an insulator?
• Approximately how many amps does the 300 W lamp draw when lit?
• Under which condition is a lead acid storage battery most likely to freeze?
• What could happen if a 40 ampere fuse is mounted in a circuit that requires a 20 ampere fuse?
• A compound motor typically features which types of fields?
• What instrument should be used to measure the current in an electric circuit?
• Which piece of electrical equipment does not require a magnetic field for its operation?
• Rosen is primarily used for what purpose?
• Why are only a few emergency lights provided for illumination in subway cars during a power loss?
• Why are polarized plugs designed with blades that are perpendicular to each other?
• What is a good insulating material that can be readily machined into the desired shape?
• How many cells are typically connected in series in a 6 volt storage battery of the lead acid type?
• In electrical circuits, what does KVA represent?
• The statement “the primary is insulated from the secondary” regarding auto transformers is?
• Which factor can influence the choice of material for transmission lines?
• What is one key characteristic of stranded wire compared to solid wire?
• A condenser operating above its rated voltage is likely to?
• For accurately measuring the shaft diameter of a motor to one thousandth of an inch, which instrument would be best?
• In subway cars equipped with lead storage batteries, for which purpose are these batteries least likely to be used?
• A photoelectric cell is primarily used to convert what type of energy?
• What is the best method to remove a slight coating of rust from small tools?
• Commutators are typically found on which type of motor?
• What is the primary use of granules of carbon in a telephone transmitter?
• Rosen is commonly used in which application?
• When measuring voltage in a circuit, which instrument would be appropriate?
• Which form of energy is usually measured in RPM?
• In an electrical circuit, what does the "ground" symbol indicate?
• Transistors are primarily used in circuits to replace which component?
• What is the minimum number of field windings required in a compound motor?
• What is the main purpose of using thin steel laminations in transformer cars?
• What metal is preferred for use in relay contacts due to its conductivity and durability?
• What is the primary effect of a condenser connected across contact points in a DC circuit?
• When fastening electrical equipment to a hollow tile wall, which fastener is considered best practice?
• What is the function of the special push button provided in a transfer switch?
• In a loaded power circuit, what is the most dangerous action to take?
• What safety precaution must be taken when using a lateral to scoop up molten solder?
• Which measurement indicates the rate of flow of electric charge in a circuit?
• The negative return for car motors is through which component?
• What does a microfarad measure in relation to condensers?
• Why is subway signal equipment such as junction boxes kept padlocked?
• What condition is created by sediment in a storage battery?
• What is one possible consequence of using the wrong fuse rating in a circuit?
• The fiber bushing inserted at the end of a flexible metallic conduit prevents what?
• What does BX commonly refer to in electrical wiring?
• If a 3 1/2 inch long nail is required for nailing wood framing members together, what size nail should be used?
• If one rail joint becomes short-circuited, how many track signal circuits will be affected?
• What is the common device used to increase the current measuring range of an ammeter?
• Why is it important to separate track signal circuits?
• What is the lowest voltage that a neon test lamp can detect?
• What type of measurement does a mega instrument provide?
• In terms of electrical wiring, what does the term 'insulation resistance' refer to?
• What function does a rheostat serve in a motor generator set?
• While lifting heavy equipment, what action should be avoided to ensure safety?
• What is the sum of 1/3 + 2/6 + 5/6?
• To operate a 6-volt lamp from a 120-volt AC source with minimal power waste, which device should be used?