Description : Etched or burned bands on the contact faces of the brushes in a direct current generator can be caused by ____________. A. high mica segments B. copper drag on the commutator C. brushes improperly positioned D. copper embedded in the brushes
Last Answer : Answer: C
Description : A flickering ground detection lamp on a DC system would indicate a _____________. A. multiple-ground condition in the distribution system B. ground in an armature coil of an operating machine C. ground in a motor accompanied with a short D. short between two adjacent bars of the generator commutator
Last Answer : Answer: B
Description : Which component is mainly used in a DC generator: a.slip ring b. commutator c. magnet d. coil
Last Answer : b. commutator
Description : Which of the listed conditions will occur if dirt and grease are allowed to accumulate between the commutator segments of a motor? A. A partial short circuit. B. A dead short circuit. C. Misalignment of the motor shaft. D. Overspeeding of the motor.
Last Answer : Answer: A
Description : In addition to undercutting the mica, proper maintenance of a D.C. motor's commutator includes _______________. A. side-cutting the copper segments and insulating the slots B. coating the copper surface with light machine ... in an oven at a maximum of 95°C for not over 8 hours D. all of the above
Description : The current from the stator of an alternator is taken out to the external load circuit through (A) slip rings. (B) commutator segments. (C) solid connections. (D) carbon brushes.
Last Answer : (C) solid connections.
Description : The insulating material used between the commutator segments is normally (a) graphite (b) paper (c) mica (d) insulating varnish
Last Answer : Ans: c
Last Answer : In case of D.C. machine winding, number of commutator segments is equal to number of armature coils.
Last Answer : The insulating material used between the commutator segments is normally mica.
Last Answer : The commutator segments are connected to the armature conductors by means of copper lugs.
Description : Temporary repairs to an open DC propulsion armature coil can be made by _____________. A. connecting the coil ends directly to a pair of negative brushes B. disconnecting coil ends, insulating ... C. grounding the coil ends and short circuiting the commutator bar D. removing the sparking brushes
Description : The distance between the starts of two consecutive coils measured in terms of coil sides is called (a) front pitch (b) winding pitch (c) commutator pitch (d) back pitch
Last Answer : (b) winding pitch
Description : A short in the shunt field of a DC motor is best located by _____________. A. visual inspection of the commutator B. applying AC voltage to each field coil and measuring the voltage drop across ... using a growler and hacksaw blade D. isolating each coil from the others and using a megohmmeter
Description : Brushes in a generator must be positioned in the neutral plane to avoid sparking between the brushes and the _____________. A. yoke B. armature windings C. field pole windings D. commutator
Last Answer : Answer: D
Description : A shunt-wound DC generator is one in which the shunt field windings are in parallel with the _____________. A. commutator B. brushes C. armature D. all of the above
Description : Which of the following components are used to convert alternating current produced in the generator windings to direct current? A. Armature and equalizer B. Commutator and brushes C. Rotor and interpoles D. Field and exciter
Description : A generator has been exposed to water and is being checked for its safe operation. Therefore, it is necessary to _______________. A. check for shorted coils with a growler B. take moisture readings with a ... a megger D. ground the commutator, or slip rings and run it at half load for 12 hours
Description : The purpose of the commutator and brushes on a DC generator is to _____________. A. transfer generated direct current voltage from the armature to the line B. convert the alternating voltage ... contact method to excite the field D. reduce sparking between the armature and the carbon brushes
Description : In an AC generator, direct current from a separate source is passed through the windings of the rotor _____________. A. by means of slip rings and brushes B. by means of a commutator C. by means of rotating bar magnet D. to minimize the danger of arc over
Description : Which one is not present in AC generator: a. Armature b. magnet c. slip ring d. commutator
Last Answer : c. slip ring
Description : Which of the following are the parts of a DC generator that convert the AC in the armature to DC in the external circuit. Are these parts the: w) field poles x) slip rings and the brushes y) commutator and the brushes z) armature and the core
Last Answer : ANSWER: Y -- COMMUTATOR AND THE BRUSHES
Description : State the function of commutator in DC generator and name the material used for commutator.
Last Answer : Function of Commutator: Commutator converts AC induced in armature winding into DC for external load. Material: i) Commutator segments are made up of Copper. ii) Commutator segments are insulated from each other by Mica.
Description : What causes sparking between the brushes and the commutator?
Last Answer : Improper commutation.
Description : (True or False) The larger the current required to produce full-scale deflection of the meter coil, the better the sensitivity of the meter.
Last Answer : False.
Description : Voltage failure of an AC generator may be caused by ____________. A. failure of the exciter generator B. a tripped bus circuit breaker C. high mica segments on the stator bus bar D. excessive prime mover speed
Description : A two-phase generator is connected to two 90Ω load resistors. Each coil generates 120 V ac. The value of current flowing through the common neutral line will be: A. 1.33 A B. 1.88 A C. 2.66 A D. 1.77 A
Last Answer : A two-phase generator is connected to two 90Ω load resistors. Each coil generates 120 V ac. The value of current flowing through the common neutral line will be: 1.77 A
Description : If two coils are wound on a single iron core, what will a change in current in one coil cause in the other coil?
Last Answer : A change in inductance.
Description : In a galvanometer, what two methods are used to indicate the amount of coil rotation?
Last Answer : The pointer arrangement and the light and mirror arrangement.
Last Answer : he pointer arrangement and the light and mirror arrangement.
Description : Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ____________. A. armature winding speed B. inductance load drop C. coil pitch factor D. armature reactance voltage drop
Description : Which of the listed electrical devices is represented by the symbol shown in the illustration? EL-0055 A. Fixed resistance resistor B. Coil with magnetic core C. DC motor or generator shunt field D. Transformer
Description : Brush sparking during commutation may be caused by ________. A. eddy currents in the armature core B. laminations in the generator field pieces C. induced current opposite to coil inductance D. coil inductance discharge occurring at commutation
Description : One method of testing for a reversed shunt field coil in a DC generator or motor is by connecting the field to a direct current source, at reduced field rated voltage, and test for ... placed near each field C. test lamp across adjacent fields D. copper jumper across the interpole connections
Description : The simplest method of controlling the terminal voltage of compound-wound DC generator is with a _____________. A. hand-operated field rheostat connected in series with the shunt field circuit B. ... in series with the load D. balance coil diverting neutral current through the shunt field
Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay
Description : A device that converts mechanical energy into electric energy is called----? A. Motor. B. Transformer. C. Coil. D. Generator?
Last Answer : B. Transformer.
Description : A device which converts chemical energy into electrical energy is called -----? A. motor B. generator C. moving-coil meter D. battery (Answer)
Last Answer : D. battery (Answer)
Description : In the plane of AC generator coil is parallel to the field, then emf induced in coil is: a. maximum b. minimum c. zero d. intermediate
Last Answer : b. minimum
Description : In the plane of the A.C generator coil is perpendicular to the field, then induced emf in the coil is: a. Maximum b. minimum c. zero d. intermediate value
Description : What happens to the H lines between the conductors of a coil when the conductors are close together?
Last Answer : The H lines cancel.
Description : When is the maximum voltage induced into a stator coil?
Last Answer : When the rotor coil is aligned with the stator coil.
Description : If the permeability of the core of a coil increases, what happens to (a) inductance and (b) true power in the circuit?
Last Answer : (a) Inductance increases; (b) true power decreases.
Description : Which oscillator uses a tickler coil for feedback?
Last Answer : Armstrong.
Description : Why is no emf induced in a rotating coil when it passes through the neutral plane?
Last Answer : No flux lines are cut.
Description : What rule should you use to determine the direction of induced emf in a coil?
Last Answer : The left-hand rule for generators.
Description : What is the effect of current flow through the coil in a d’Arsonval meter movement?
Last Answer : A magnetic field is generated around the coil and the attraction of this field with the permanent magnet causes the coil to move
Description : What is the primary disadvantage of the pointer arrangement for indicating coil rotation?
Last Answer : Coil balance.
Description : What physical component of a galvanometer provides the restoring force for the coil?
Last Answer : Phosphor bronze ribbons.