Description : In a commutator (a) copper is harder than mica (b) mica and copper are equally hard (c) mica is harder than copper (d) none of the above
Last Answer : Ans: c
Description : The insulating material used between the commutator segments is normally (a) graphite (b) paper (c) mica (d) insulating varnish
Description : Brushes of D.C. machines are made of (a) carbon (b) soft copper (c) hard copper (d) all of above
Last Answer : Ans: a
Description : Copper brushes in D.C. machine are used (a) where low voltage and high currents are involved (b) where high voltage and small cur-rents are involved (c) in both of the above cases (d) in none of the above cases
Description : In D.C. generators, current to the external circuit from armature is given through (a) commutator (b) solid connection (c) slip rings (d) none of above
Description : In lap winding, the number of brushes is always (a) double the number of poles (b) same as the number of poles (c) half the number of poles (d) two
Last Answer : Ans: b
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 : Which of the listed conditions might contribute to very rapid wearing of a DC machine's commutator bars? A. A grounded commutator bar B. Using improper carbon brushes C. Aligning the front and rear mica V-rings improperly D. An open circuit in the armature
Last Answer : Answer: B
Description : Iron losses in a D.C. machine are independent of variations in (a) speed (b) load (c) voltage (d) speed and voltage
Description : Which of the listed faults cannot be eliminated, EXCEPT by turning or grinding a commutator with a rigidly supported tool? A. Sparking brushes B. Eccentricity C. High mica D. Blackened commutator
Description : In case of D.C. machines, mechanical losses are primary function of (a) current (b) voltage (c) speed (d) none of above
Description : A separately excited generator as compared to a self-excited generator (a) is amenable to better voltage con-trol (b) is more stable (c) has exciting current independent of load current (d) has all above features
Last Answer : Ans: d
Description : In a four-pole D.C. machine (a) all the four poles are north poles (b) alternate poles are north and south (c) all the four poles are south poles (d) two north poles follow two south poles
Description : The field coils of D.C. generator are usually made of (a) mica (b) copper (c) cast iron (d) carbon
Last Answer : Ans: b (b) copper
Last Answer : The material for commutator brushes is generally carbon.
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
Last Answer : Answer: A
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 : Which of the following precautions should you take when securing propulsion generators and motors for an extended period of time? A. Disconnect the brush pigtails from their contacts and circulate air ... Lift the brushes from commutator collector rings and circulate cool dry air through the units.
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 : _____ brushes are fragile and cause excessive wear of commutator, (a) Natural graphite (b) Hard carbon (c) Electro graphitic (d) Metal graphite
Last Answer : (a) Natural graphite
Description : Which is an amorphous material? (A) Glass (B) Mica (C) Brass (D) Cast iron
Last Answer : (A) Glass
Description : Which of the diagrams shown in the illustration depicts the proper method of aligning brushes on a commutator? EL-0057 A. A B. B C. C D. D
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 : Which of the following is a characteristic of fractional horsepower repulsion start motors? A. They start with a rotating stator field. B. The short circuiting ring is removed from the commutator while ... brushes are removed from the commutator while starting. D. They have a low starting torque.
Description : Sparking at the brushes of a running motor could be an indication of _____________. A. normal operation B. a dirty commutator C. increased brush capacity D. water vapor absorption
Description : In the illustrated test, if the lamp fails to light on any of the three windings then _________. EL-0027 A. all three windings are grounded and the motor should be sent out for repair B. ... the motor controller and the controller should be checked D. the test should be redone at a higher voltage
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 function of the commutator in a DC motor is to ________. A. reverse the flow of current through the armature B. reverse the flow of current in the field poles C. reduce the reluctance of the magnetic path through the motor D. shift the neutral running plane of the brushes to prevent sparking
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 : 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 : Voltage generated by most AC generators is fed from the machine to the bus by means of ____________. A. brushes on a commutator B. brushes on slip rings C. slip rings on a commutator D. direct connections from the stator
Description : What causes sparking between the brushes and the commutator?
Last Answer : Improper commutation.
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
Last Answer : The number of brushes in a commutator depends on amount of current to be collected.
Last Answer : In D.C. generators, the brushes on commutator remain in contact with conductors which lie under interpolar region.
Last Answer : Commutator brushes are made up of carbon.
Description : A shorted armature coil in a DC motor can be detected by _____________. A. sparking at the brushes B. shiny armature coil C. worn grooves in the armature D. undercut mica
Description : Mixing vessel used for the chlorination of methane to produce methyl chloride is made of (A) Copper (B) Cast iron (C) Aluminium (D) High carbon steel
Last Answer : (B) Cast iron
Description : Which of the following material of construction may be recommended by a chemical engineer for handling a gaseous chlorine (dry or wet) stream in a fluid flow system? (A) High silicon iron, silicon rubber ... Mild steel and stainless steel (C) Cast iron, tin and aluminium (D) Copper, nickel and Monel
Last Answer : (A) High silicon iron, silicon rubber, Kel-F and Teflon
Description : Ball bearings are generally made of (A) Plain carbon steel (B) Chrome carbon steel (C) Stainless steel (D) Malleable cast iron
Last Answer : (B) Chrome carbon steel
Description : Galvanising is generally done on (A) Non-ferrous metals (B) Low carbon steel (C) Stainless steel (D) Cast iron
Last Answer : (B) Low carbon steel
Description : Material of construction of pipe generally used for conveying water in India is (A) Stainless steel (B) Cast iron (C) Wrought iron (D) Lead lined steel
Description : The Vindhyan system of rocks is important for the production of [CDS 2011] (a) precious stones and building materials (b) iron ore and manganese (c) bauxite and mica (d) copper and uranium
Last Answer : Ans: (a)
Description : India has the monopoly in the International market in the supply of– (1) Iron (2) Mica (3) Bauxite (4) Copper
Last Answer : (2) Mica Explanation: India produces approximate 90 % of the world's mica. It is an indispensable component of the electrical industry. India accounts for 60 % of mica embarking in international trade.
Description : Aqueous nitric acid is stored in __________ vessel. (A) Plain carbon steel (B) Stainless steel (C) Cast iron (D) Thermosetting plastic material
Last Answer : (C) Cast iron
Description : The material used for making torsion bar is (a) Steel (b) Cast iron (c) High carbon steel (d) All of the above
Last Answer : (a) Steel
Description : Which material is suitable for shaft material? a. High speed steel b. Stainless steel or high carbon steel c. Grey cast iron d. Steel having approx. 0.4% carbon and 0.8% manganese
Last Answer : d. Steel having approx. 0.4% carbon and 0.8% manganese
Description : In which of the following industries is mica used as a raw material? (a) Electrical (b) Iron and steel (c) Toys (d) Glass and pottery
Last Answer : Ans:(a)
Description : The material used in the manufacture of lead pencil is – (1) Graphite (2) Lead (3) Carbon (4) Mica
Last Answer : (1) Graphite Explanation: Pencils create marks via physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface. They are noticeably distinct from ... of graphite mixed with a clay binder, leaving grey or black marks that can be easily erased.