140 True/False questions
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If four cables all have the same insulation and circular mil value, which cable would be the most flexible? → 200 strands.
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When dealing with electrical equipment, grounding: → Provides a return path to the earth and prevents voltage from existing on the frames of the equipment.
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A hot stick shall be electrically tested: → The action of an electrical current which carries away particles of a conductor.
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A solid state device most commonly used to control power output in a DC circuit is: → Silicon controlled rectifier.
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The unit of measurement generally used when rating a capacitor is the: → Volt.
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What is the same across each part of a parallel circuit? → The amount of current that a breaker can carry under normal conditions.
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When fuses are too big for the current requirement of the equipment being protected: → Too much current could be allowed to pass through, overheating. equipment and burning off insulation.
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Five kilowatts equal how many watts? → Overload and single-phase protection on three-phase circuits.
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The device that makes or breaks a circuit feeding a load is called a: → Contactor.
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A wire used for a temporary connection is termed a: → Jumper.
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When comparing the resistance of the shunt field of a DC motor to the series field, the shunt field resistance is usually: → Ohm.
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A single element fuse provides: → Current in one direction.
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Electrical pressure or electromotive force is defined as: → Voltage.
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The safest way to check an electrical load to see if it is an open circuit is with a (an): → Ohmmeter with power off.
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What will happen to a DC shuttle car series wound motor if the chain or drive shaft would break? → The motor will overspeed to the point of destruction.
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Three-pole single-throw disconnect switches have how many knife blades? → Three.
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The main function of a thermal overload is to: → Motor
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Arc chutes on contactors contain heavy copper coils that are called: → Blowout coils.
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If you were to shunt-out a resistor, the resistor would: → Not cause a voltage drop.
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If the continuous miner stops operating, and the only component that is energized on the miner is its methane monitor, you could do all of the following EXCEPT: → Protect the motor from overload.
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What is electrolysis? → The action of an electrical current which carries away particles of a conductor.
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If a voltmeter were placed across the fuse and no voltage was indicated, you could correctly assume that: → The fuse was good
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The motor overload relay contacts are connected in: → KVA rating.
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Resistance is checked with an instrument called a(an): → Ohmmeter
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If a thermal overload activates, causing a circuit to be de-energized, what must you do before the circuit can be re-energized? → Allow it to cool.
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If the shunt field of a compound motor opens, the motor usually: → Speeds up.
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Heat sinks on a rectifier are provided to: → Short circuit protection.
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The most commonly used short-circuit protective device for trailing cables is: → A circuit breaker.
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Which system requires only two power conductors and is generally used for control, lighting, and small loads? → Current remains the same at all loads.
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When an overcurrent device detects an overload condition, the breaker should trip: → All three phases at the same time.
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Which of the following is a true statement concerning the operational characteristics of an SCR? → It will allow current flow in only one direction once it is gated.
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A diode blocks: → Changes AC current to DC current.
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When testing a diode with an ohmmeter, what will be the reading of a good diode? → Rectifiers.
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If you read an open circuit between A1 and A2 of a DC motor, it indicates that: → Reverse either the armature or the series field leads.
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Current is checked with an instrument called a (an): → Momentary.
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To reduce the hazard of electrical shock, which of the following should be installed? → Voltage.
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Which of the following methods is NOT recommended for removing a victim from contact with electricity? → Knock the victim off with a nonconductive object.
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If you were to peel the insulation off a No. 14 AWG stranded conductor, you would expect to find: → Smaller wires which are not insulated from one another.
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What is used to prevent the Forward and Reverse contactors in a motor reversing control from operating at the same time? → Electrical and/or mechanical interlocks.
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Which of the following is a good conductor of electricity? → A variable resistance in a separate field circuit.
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This stop switch is classified as: → Proper fuses.
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The component attached to the donut coil on one phase lead, between the contactors and motor, is normally used as a (an): → Ammeter
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What is used to limit the starting current of a DC motor? → Resistors.
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Speed of DC motors can be controlled by: → Regulating the applied voltage.
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To reverse the direction of a DC motor: → Reverse either the armature or the series field leads.
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Through what piece of equipment is alternating current fed in order to lower its voltage? → Transformers.
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The main purpose of the overloads is to protect the: → Motor
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A blown fuse or a tripped circuit breaker could indicate all of the following EXCEPT: → Overvoltage.
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Voltage is checked with an instrument called a (an): → Current.
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The overload relay contacts of a thermal overload are generally connected in: → S1and S2.
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The current used for charging storage batteries is: → Stop the drive when the belt is slipping.
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Electron flow in a conductor is defined as: → Current.
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The material used to separate one electrical wire from another in a cable is called: → Insulation.
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Charging a 12-volt battery from a 12-volt AC source will: → The amount of current that a breaker can carry under normal conditions.
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There are three types of electrical diagrams. Which of the following is NOT an electrical diagram? → Power diagram.
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A small sump pump blows a 20-amp fuse. The pump under full load draws 12 amps of current and receives its power through a No. 12 AWG cable. After repairing the problem, you discover you only have a 15-amp and a 30-amp fuse. You should: → Install the 15-amp fuse
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Magnetic trip units of a circuit breaker provide what protection? → An electromagnetic field.
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When a circuit breaker has an overload trip, what causes the circuit breaker to de-energize the circuit? → A thermal element heats up and actuates the contacts.
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The safest way to de-energize a motor running on full load is: → A shunt motor.
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Thirty-five horsepower is equal to: → 26.11KW.
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With a shunt motor, speed is controlled by: → A variable resistance in a separate field circuit.
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Fuses should be replaced with: → Current in one direction.
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A shuttle car tramming up a steep grade at the feeder blows a fuse. Before knocking the power and tagging-out the circuit you must: → Block the machine so it doesn't move.
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If an ohmmeter shows continuity across an SCR with no gate voltage applied, the SCR is probably: → The fuse was blown.
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What is the purpose of a frame ground in a trailing cable? → Stop the drive when the belt is slipping.
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Shunt fields of a DC motor are identified by: → F1 and F2 leads.
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The system using one ground wire and three hot wires, whose voltage is balanced 120 degrees apart is called: → Three-phase.
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How is the rotation of a direct current, series motor reversed? → Current.
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The thermal heater element of an overload relay is generally connected in: → Series with the operating coil.
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A magnetic relay is either closed or opened by: → An electromagnetic field.
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The difference between a time delay and an instantaneous overcurrent relay: → Lies primarily in how quickly they trip a circuit breaker.
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If circuit breakers are too small for the equipment they are protecting: → The circuit breaker will not stay closed.
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What is the effect of dust and dirt between joints of permissible equipment? → Joints cannot be closed tightly enough to get the required cooling action; therefore permissibility is destroyed.
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In general, how should bandages be applied to a burn? → Loosely.
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When checking resistance in an AC circuit when troubleshooting, what initial precaution must be taken? → Higher.
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If the cross-sectional area (size) of a wire is decreased, its resistance will: → Increase
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What device may be installed in the neutral of a three-phase wye connected system to limit the current if a ground fault occurs? → Higher.
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The direction in which a motor rotates depends upon the: → Direction of the current flow through the armature.
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The unit of measurement of resistance to the flow of electricity is the: → Volt.
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What happens if the two line leads to a DC series motor are reversed? → Direction of rotation remains the same.
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Which of the following is not a characteristic of a series motor? → Resistors.
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If you wanted to check the insulation on wire for damage, the instrument you would use is a (an): → Megger.
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Thermal heater strips in circuit breakers or line starters are used to provide what protection? → Overcurrent.
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The heater element in a motor circuit overload relay is connected in: → Maximum time period it can safely operate.
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When a circuit breaker is tripped: → No current flows beyond it into the circuit.
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A transformer has primary windings of 460 volts and secondary windings of 115 volts. What can you correctly assume about wire size? → A megger.
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The ampere capacity of a circuit breaker is: → No current flows beyond it into the circuit.
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Meggers are used to check: → Insulation resistance.
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The function of the capacitor trip device and circuit is to: → Stop the drive when the belt is slipping.
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A ground monitor circuit is used to: → Overload and single-phase protection on three-phase circuits.
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If you checked a resistor marked 50 ohms and your meter read the resistance extremely high (your meter would not measure the amount), you would be most correct in assuming that: → Increase
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The unit of measurement meaning "electrical pressure or force" is the: → Volt.
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The duty cycle of a motor refers to its characteristic: → Maximum time period it can safely operate.
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Two resistors (Resistor 1 and Resistor 2) are connected in parallel and Resistor 2 burns open. What would happen? → Voltage.
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Thermal overloads are used for: → Overload and single-phase protection on three-phase circuits.
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A ground fault is a phase-to-ground short in the output of: → An electrical system.
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Which will cause the power center circuit breaker for a continuous miner to trip faster? → Series with the motor circuit.
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The wires of a transformer have a 10:1 ratio. When stretched out side by side: → KVA rating.
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A wire is marked "14 AWG". The number "14" refers to: → Protect the motor from overload.
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If neither indicating light were on, and the coil would not energize, what component is most likely defective? → Protect the motor from overload.
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Pumps and section equipment are grounded by a: → A conductor connected to the system ground.
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What purpose is served by a starting resistor in a motor circuit? → It helps to extinguish the arc when the contactor opens.
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A current that changes in magnitude but not in direction is called? → Jumper.
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What is the same in all parts of a series circuit? → Voltage.
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The idea behind a capacitor trip device and circuit is to: → Provide sufficient energy to trip the breaker, even after the power goes off.
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When compared to the resistance of the series fields and armature circuit, the shunt fields of a motor will have: → Motor
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The DC motor that uses both a series and shunt winding and combines the characteristics of both is called a: → Compound motor.
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If a circuit breaker with thermal overload protection has just tripped and you immediately try to re-energize the circuit and find that the breaker will not hold in, you should: → No current flows beyond it into the circuit.
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If the motor developed an internal "direct short" between phases, the device to de-energize the circuit would be the: → Circuit breaker.
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Series field leads of a DC motor are identified by: → S1and S2.
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If under normal load a 30-amp fuse becomes hot the most likely reason for this is: → The pump should start because the float switch completed an electrical circuit
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If an equipment frame grounding wire was not provided: → Short circuit and overload protection.
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Of the devices listed below, what will change single-phase AC to DC? → Rectifiers.
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If 1,100 amps leave a rectifier on one conductor, how many amps will return to that rectifier on the other conductor? → 1,100 amps.
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If you wanted to find information concerning a motor's duty cycle characteristics, you could find it most easily by: → Maximum time period it can safely operate.
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If a voltmeter were placed across the fuse and the scale indicated 120 volts, you could correctly assume that: → The fuse was good
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What purpose is served by a blowout coil used as a DC contactor? → It helps to extinguish the arc when the contactor opens.
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The power of a transformer is rated by its: → 26.11KW.
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If the cross-sectional area (size) of a wire is decreased, its resistance will → Increase
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A rectifier does what: → Insulation resistance.
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A solenoid operates in the same way as a: → Short circuit protection.
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If a float switch on a pump closes because the water level rises: → Cool the rectifier.
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The motor better suited to control hoisting is: → Momentary.
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The purpose of a slip switch on a belt is to: → Stop the drive when the belt is slipping.
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A dual element fuse provides: → Insulation resistance.
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If a belt conveyor loaded with coal was turned on, the starting torque would be greatest when the motor: → Resistors.
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If you were to lockout and tag the motor to begin repair work, the safest and most convenient place to do this would be at the: → Smaller wires which are not insulated from one another.
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If a 120-volt direct current source is connected to a 10:1 step-down transformer, the output on the secondary side is: → Zero volts.
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Which would require the largest wiring? → A 15-HP, 220-volt motor.
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If the overcurrent condition continues for a long time, and at a great enough magnitude, an overcurrent device will trip the: → Circuit breaker.
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The instantaneous setting of a circuit breaker is: → The short circuit setting.
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A 3-phase motor continues to operate when one lead has been severed or cut in two; then, when stopped, will not start again. The motor is said to be: → Single phase.
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If a diode reads continuity in one direction and open in the other, it is probably: → Good.
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Transformers are used to: → Current in one direction.
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Using a shunt motor enables you to control: → A variable resistance in a separate field circuit.
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If a transformer was believed to be shorted because of a breakdown in its insulation, what instrument would you use to check it? → A megger.
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If you read a low resistance between leads S1 and S2 of a series motor, means that: → Not cause a voltage drop.
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If a system designed for a 20-amp fuse blows, and an electrician replaces it with one rated at 30 amps: → A fire may result or the equipment may become damaged.
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What is wrong with replacing a blown fuse with a piece of copper wire? → The copper wire will not provide adequate overcurrent protection.
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The part of a disconnect switch which has metal blades that pivot at one end is called a (an): → Knife switch.