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Theory - Mike Holt
| Question | Answer |
|---|---|
| Providing a path to the earth often helps reduce electrostatic charge. (A) True (B)False | A- true |
| Lightning frequently terminates to a point of elevation and strikes nonmetallic as well as metallic objects with the same frequency. (A) True (B)False | A- true |
| The termination of the lightning strike is likely to ignite combustible materials. (A) True (B)False | B- false |
| Lightning protection is intended to protect the building itself, as well as the electrical equipment on or inside the structure. (A) True (B)False | B-false |
| Non-magnetic metals are ferrous, meaning they do not contain any iron, and cannot be magnetized. (A) True (B)False | B-false |
| Magnetic lines of force can cross each other and they are called flux lines. (A) True (B)False | B-false |
| It is not the force of the magnetic field through a conductor that produces electricity; it is the relative motion of the field to the electrons within the conductor that produces the movement of electrons. (A) True (B)False | A-true |
| People become injured and death occurs when voltage pushes through the human body causing the heart to go into ventricular fibrillation. (A) True (B)False | A-true |
| The severity of an electric shock is dependent on the current flowing though the body, which is impacted by circuit voltage and contact resistance. (A) True (B)False | A-True |
| An electrical arc blast can approach ______, which vaporizes metal parts and produces an explosive and deadly wave. (A) 10,000 °F (B) 15,000 °F (C) 25,000 °F (D) 30,000 °F (E) 35,000 °F | D- 30,000 °F |
| If a conductor carrying current is next to another conductor varying current in the opposite direction, the electromagnetic field attempts to push the conductors apart. (A) True (B) False | A-True |
| A clamp-on ac meter has a coil that is clamped around the conductor and detects the rising and falling ______ field being produced due to the ac flow through the conductor. (A) Static (B) current (C) power (D) magnetic | D- magnetic |
| Ohmmeter measure the ________ or opposition to current flow of a circuit or component. (A) Voltage (B) Current (C) Power (D) resistance (E) Reactance | (D) resistance |
| The meg meter is used to measure very high-_____ values, such as those found in cable insulation, or motor and transformer windings. (A) voltage (B) reactance (C)power (D)current (E)resistance (F)magnetic wave | E- resistance |
| The electric motor works on the principle of the attracting and repelling forces of _______ fields. (A) Voltage (B) current (C) power (D) magnetic | D- Magnetic |
| The ________ of a generator is forced to rotate while it is being subjected to the magnetic field of the stator. (A) winding (B) rotor (C) stator (D) b or c | B-rotor |
| A holding relay is primarily used for worker convenience. (A) True (B) False | B- false |
| According to the Electron Current Flow Theory, electrons flow away from the negative terminal of the source, through the circuit and load, toward the positive terminal of the source. (A) true (B) false | A-True |
| According to the conventional current flow theory, electrons travel from positive to negative. (A) True (B) False | a- True |
| The major advantage of ac over dc is the ease of voltage regulation by the use of a transformer. (A) True (B) False | A- true |
| The best conductors, in order of their conductivity, are gold, silver, copper, and aluminum. (A) True (B) False | b-false |
| In a dc circuit, the only opposition to current flow is the physical resistance of the material. This opposition is called “reactance” and is measured in ohms. (A) True (B) False | B-false |
| The formulas in the power wheel apply to _____. (A) dc (B) ac with unity power factor (C) dc or ac circuits (D) a and b (E) ac and series dc circuits | D- a and b |
| The opposition to current flow results in voltage drop. (A) True (B) False | A- true |
| Kirchoff’s Voltage law states, “ In a series circuit, the sum of the voltage drops across all of the resistors will equal to the applied voltage.” (A) True (B) False | A-True |
| Kirchoff’s Current law states, “In a series circuit, the current is _______ through the transformer, the conductor, and the appliance.” (A) proportional (B) distributed (C) additive (D) the same | D- the same |
| According to Kiirchoff’s law, the total current provided by the source to a parallel circuit will equal the sum of the currents of all of the branches. (A) True (B) false | A- True |
| The total resistance of a parallel circuit can be calculated by the ________ method. (A) equal resistance (B) product-over-sum (C) reciprocal (D) any of these | D- any of these |
| When the power supplies are connected in parallel, the voltage remains the same, but the current or amp-hour capacity will be increased. (A) True (B) false | A-true |
| A balanced 3-wire 120v/240v, single-phase circuit is connected so that the ungrounded conductors are from different transformer phases (line 1 and line 2). The current on the neutral conductor will be (?0,70,80,or100?) % of the ungrounded conductor. | The answer is 0%. |
| If the ungrounded conductors of a multiwire circuit are not terminated to different phases, this can cause the neutral current to be in excess of the neutral conductor rating. (A) True (B) false | A-true |
| The current flowing on the neutral conductor of a multiwire circuit is called “unbalanced current.” (A) True (B) false | A-true |
| Improper wiring of mishandling of multi-wire branch circuits can cause ____ connected to the circuit. (A) overloading of the ungrounded conductors (B) overloading of the neutral conductors (C) destruction of equipment because of over voltage (D) b & c | D- b & c |
| Because of the dangers associated with an open neutral conductor, the continuity of the _____ conductor cannot be dependent upon the receptacle. (A) ungrounded (B) grounded (C) a&b (D) none of these | B- grounded |
| Electrons leaving a power supply are always trying to return to the same power supply; they are not trying to go into the earth. (A) True (B) false | A- true |
| To prevent fires and electric shock, the NEC specifies that neutral current can flow on metal parts of the electrical system. (A) True (B) false | B- false |
| Metal parts of premises wiring must be bonded to a low impedance path designed so that the circuit protection device will quickly open and clear a ground fault. (A) True (B) false | A-true |
| Because of the earth’s high resistance to current flow, it cannot be used for the purpose of clearing a line-to-case ground fault _______ wiring. (A) utility (B) premises (C) a or b (D) none of these | B- premises |
| Over current is current in excess of the rated current of equipment or conductors. It may result from a(n) ____. (A) overload (B) short circuit (C) ground fault (D) all of these | D- all of these |
| To protect against electric shock or to prevent a fire, a dangerous ______ must quickly be removed by opening the circuit’s over current protection device. (A) overload (B) Short circuit (C) ground fault (D) all of these | D- all of these |
| Inverse time breakers operate on the principle that as the current decrease, the time it takes for the device to open. (A) True (B) false | B-false |
| The _____ sensing element causes the circuit breaker to open when a predetermined calibration temperature is reached. (A) magnetic (B) electronic (C) thermo (D) none of these | C- thermo |
| The magnetic time-delay circuit breaker operates on the solenoid principle where a movable core, held with a spring, is moved by the magnetic field of a(n) _____. (A) overload (B) short circuit (C) ground fault (D) b or c | D- b or c |
| Available short circuit current is the current in amperes available at a given point in the electrical system. (A) True (B) false | A- true |
| Factors that affect the available short-circuit current include transformer ______. (A) voltage (B) KVA rating (C) impedance (D) all of these | D- all of these |
| Factors that affect the available short-circuit current include circuit conductor _____. (A) meterial (B) size (C) length (D) all of these | D- all of these |
| Circuit breakers and fuses are intended to interrupt the circuit, and they must have an ampere interrupting taking (AIR) sufficient for the available short-circuit current. (A) True (B) false | A- true |
| If the protection device is not rated to interrupt the current at the available fault values at its listed voltage rating, it can explode while attempting to clear the fault. (A) True (B) false | A- true |
| Equipment must have a(n) ____ current rating that permits the protection device to clear a short circuit or ground fault without extensive damage to the components of the circuit. (A) overload (B) short circuit (C) ground-fault (D) b or C | B- short circuit |
| A GFCI is designed to protect persons against electric shock. It operates on the principle o monitoring the imbalance of current between the circuit’s _____ conductor. (A) ungrounded (B) grounded (C) equipment (D) a and b | D- a & b |
| A GFCI-protection device contains an internal monitor that prevents the device from being turned on if there is a neutral-to-case connection downstream of the device, but this only occurs if there is a load on the circuit. (A) True (B) false | B- false |
| Severe electric shock or death can occur if a person touches the ungrounded and the neutral conductors at the same time, even if the circuit is GFCI- protected. (A) True (B) false | A- True |
| Typically, when a GFCI-protection device fails, the switching. Contacts remain closed and the device will continue to provide power without GFCI protection. (A) True (B) false | A- true |
| Arcing is defined as a luminous discharge of electricity an insulating medium. Electric arcs. Operate at tempatures between ____ and expel small particles of very hot molten material. (A) 10,000 & 25,000 F (B) 2,000 & 10,000 F (C) 5,000 & 15,000 F | C- 5,000 & 15,000 F Arc blasts can reach 30,000 F |
| Unsafe arcing faults can occur in one of two ways, as series arcing faults or as parallel arcing faults. The most dangerous is the parallel arcing fault. (A) True (B) False | A- true |
| An AFCI-protection device provides protection from an arcing fault by recognizing the characteristics unique to an arcing fault and by functioning to de-energize the circuit when an arc fault is detected. (A) True (B) False | A- TRUE |
| A nonsinusoidal waveform is created when _____ loads distort the voltage and current sine wave. (A) linear (B) resistive (C) inductive (D) nonlinear | D- nonlinear |
| When describing the relationship between voltage and current, the reference waveform is always ____. (A) current (B) resistance (C) voltage (D) none of these | C- voltage |
| The effective value is equal to the peak value _____. (A) times 0.707 (B) times 1.41 (C) times 2 (D) times 1.732 | A- times .707 |
| Even when power is removed from the circuit, capacitors can store large amounts of energy for.a long period of time. They can discharge and arc if inadvertently shorted or grounded out. (A) True (B) False | A- true |
| The opposition offered to the flow of ac current by a capacitor is called “ capacitive reactance,” which expressed in ohms and abbreviated ______. (A) Xc (B) XL (C) Z (D) none of these | A- XC |
| Induced voltage in the conductor carrying alternating current opposes the change in current flowing through the conductor.Induced voltage that opposes the current flow is called? (A) CEMF (B) counter-electromotive force (C) back-EMF (D) all of these | D- all of these |
| For ac circuits, the ac ___ of a conductor must be taken into consideration. (A) eddy currents (B) skin effect (C) resistance (D) none of these (E) a, b and c | E- a, b and c |
| This is the expanding & collapsing magnetic field within the conductor induces a voltage in the conductors that repels the flowing electrons towards the surface of the conductor. (A)eddy currents (B)induced voltage (C)impedance (D)skin effect | D- skin effect |
| The abbreviation for impedance is _____. (A) Xl (B) Xc (C) Z (D) R (E) non of these | C- Z |
| Self induced voltage opposes the change in current flowing in the conductor. This is called “inductive reactance” and it is abbreviated ____. (A) XL (B) Xc (C) Z (D) IR (E) non of these | A- XL |
| AC inductive or capacitive reactive loads cause the voltage and current to be in-phase with one another. (A) True (B) False | B- False |
| Dual-voltage ac motors are made with 2 field windings. The field windings are connected in ____ for low-voltage operation and in ____ for high-voltage operations. (A) series, parallel (B) Parallel, series (C) series, series (D) parallel, parallel | B- parallel, series |
| The motor FLA rating is used when sizing motor conductor size or circuit protection. (A) True (B) False | B- false |
| When a motor starts, the current drawn is approximately ____ times the motor FLA; this is known as “motor locked-rotor amperes” (LRA) (A) 0.80 (B) 1.25 (C) 3 (D) 6 | D- 6 |
| Rotating part of motor jammed, no rotation, no CEMF produced in winding. Results the motor operates @ ____ & the windings will be destroyed by excessive heat. (A)FLA (B)FLC (C)LRC (D)any of these | C- LRC |
| In an induction motor, the stator produces a rotating magnetic field that induces current in the rotor windings. The rotor current generates a magnetic field in opposition to the magnetic field of the stator, thereby causing the rotor to turn. True/false | True |
| In a(n)___ motor, the rotor is locked in step with the totating stator field and is dragged along at the speed of the rotating magnetic feild. (A) wound-rotor (B) induction (C) synchronous (D) squirrel-cage | C- synchronous |
| ____ motors are fractional HP motors that operate equally well on ac & dc & are used for vacuum cleaners, electric drills, mixers, and light household appiances. (A) AC (B) Universal (C) wound-rotor (D) syncronous | B- Universal |
| Swapping ____ of the line conductors can reverse a three-phase ac motor’s rotation. (A) one (B) two (C) three (D) four | B- two |
| The ____ of an ac generator contains the electromagnetic field, which cuts through the stationary conductor coils. (A) stator (B) rotor (C) coil (D) winding | B- rotor |
| Three-phase ac generators have 3 equally spaced windings _____ out-of-phase with each other. (A) 90 degrees (B) 120 degrees (C) 180 degrees (D) 360 degrees | B- 120 degreeds |
| The energy transfer ability of a transformer is accomplished because the primary electromagnetic lines of foce induce a coltage in teh secondary winging. (A) True (B) False | A- true |
| Voltage induced in the secondary winding of a transformer is dependent on the number of secondary turns as compared to the number of primary turns. (A) True (B) False | A- True |
| Wasteful circulating ____ in the iron core cause(s) the core to heat up without any useful purpose. (A) conductor resistance (B) flux leakage (C) eddy currents (D) hysteresis losses | C- eddy currents |
| ____ can be reduced by dividing the core into many flat sections or laminations. (A) conductor resistance (B) flux leakage (C) eddy currents (D) hysteresis losses | C- eddy currents |
| Current flows through Transformer; the iron core is temporarily magnetized. Energy required to realign the core molecules to the changing electromagnetic field is called ? loss. (A)conductor resistance (B) flux leakage (C) eddy currents (D) hysteresis | D- hysteresis |
| 3-phase, ___, wye-connected systems can overheat because of circulating odd triples harmonic currents. (A) 2-wire (B) 3-wire (C) 4-wire (D) parallel (E) series | C- 4-wire |
| The hearing from harmonic currents is proportional to the square of the harmonic current. (A) True (B) False | A- true |
| Result of conductor resistance: flux leakage, eddy Currents, & hysteresis losses, not all input power is transferred to the secondary winding for useful purposes. (A) True (B) False | A- true |
| If the primary phase voltage is 480v and the secondary phase voltage is 240v, the turns ratio is ___.. (A) 1:2 (B) 1:41 (C) 2:1 (D) 4:1 | C- 2:1 |
| Transformers are rated in _____. (A) VA (B) kW (C) W (D) kVA (E) any of these | D- kVA |
Created by:
loran