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Commutator brushes are made up of carbon.

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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

Answer : ANSWER: Y -- COMMUTATOR AND THE BRUSHES

Answer : The number of brushes in a commutator depends on amount of current to be collected.

Answer : In D.C. generators, the brushes on commutator remain in contact with conductors which lie under interpolar region.

Answer : The material for commutator brushes is generally carbon.

Description : What are camel haired brushes made of

Answer : Squirrels tails

Answer : Brushes of D.C. machines are made of carbon.

Description : Brushes of DC machine are made up of ?

Answer : Brushes of DC machine are made up of carbon.

Description : Carbon brushes are used in electric motors to:  (1) Brush off carbon deposit on the commutator (2) Provide a path for flow of current (3) Prevent overheating of armature windings (4) Prevent sparking during commutation

Answer : Carbon brushes are used in electric motors to: Provide a path for flow of current.

Description : The distance between two coil sides which are connected to the same commutator segment is called as  (1) winding pitch (2) back pitch (3) front pitch (4) full pitch

Description : In a DC motor, it is important to place the brushes along ______ A) Magnetic Neutral Axis B) Normal Geometric Axis C) Nominal Geometric Axis D) None of these

Answer : In a DC motor, it is important to place the brushes along Magnetic Neutral Axis

Description : In a DC shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will   (a) Improve but terminal voltage will fall   (b) ... will fall   (c) Improve and terminal voltage will rise   (d) worsen and terminal voltage will rise 

Answer : In a DC shunt generator working on load, the brushes are moved forward in the direction of rotation, as a result of this, commutation will Improve but terminal voltage will fall 

Answer : If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be crossmagnetisation as well as demagnetising.

Answer : Copper brushes in D.C. machine are used where low voltage and high currents are involved.

Description : State the function of following parts of DC motor : i) Yoke ii) Poles iii) Field winding iv) Commutator. 

Answer : Function : i) Yoke: The yoke serves the following two purposes. i) It supports the other components such as poles and provides mechanical protection for whole machine. ii) It forms a part of ... one pole to another and thus to help the motor to develop a continuous and unidirectional torque  

Description : Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is (A) 48 (B) 24 (C) 192 (D) 96

Answer : Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is 24

Description : Commutator is used in  (a) DC generator (b) AC generator (c) invertors (d) convertors

Answer : Used in DC generators.

Answer : The commutator segments are connected to the armature conductors by means of copper lugs.

Answer : In a A.C. series motor armature coils are usually connected to commutator through resistance.

Description : For a DC motor, what major component in addition to the field winding and the armature winding is necessary? w) a commutator x) a stator y) a battery z) a rotor

Answer : ANSWER: W -- A COMMUTATOR

Description : While calculating performance of medium transmission line, what assumptions are made in case of (i) Nominal 'T' Method (ii) Nominal 'TT' Method. 

Answer : (i) Assumptions are made in case of Nominal 'T' Method:  a. It is assume that line capacitance is connected at center of transmission line. b. It is assume that half ... assumed that transmission line resistance & reactance per phase is connected in between two half transmission line capacitance 

Answer : Ceramic capacitor is made up of ceramic material layers where ceramic material is a dielectric material.

Description : State the function of following parts of slip ring induction motor: (i) Slip ring (ii) Fan (iii) Brushes (iv) Frame

Answer : Sr. No. Name of part Function 1 Slip ring 1) The rotor winding terminals are permanently connected to the slip rings. 2) Connects external resistance to rotor circuit through ... It provides mechanical support to the entire internal parts of motor. 2) Protects the inner parts.

Description : The number of brushes in a 6-pole double-layer lap wound dc machine is (A) 8 (B) 6 (C) 4 (D) 2 

Description : Electrical contact materials used in switches, brushes and relays must possess   (A) high thermal conductivity and high melting point  (B) Low thermal conductivity and low melting point   (C) High thermal conductivity and low melting point  (D) Low thermal conductivity and high melting point.

Answer : Electrical contact materials used in switches, brushes and relays must possess high thermal conductivity and high melting point 

Answer : The rapid wear of brushes takes place due to abrasion from dust, excessive spring pressure, rough commutator bars, high mica insulation between com-mutation bars.

Answer : Armature coil is short circuited by brushes when it lies along neutral axis.

Answer : In lap winding, the number of brushes is always same as the number of poles.

Description : State the function of commutator in DC generator and name the material used for commutator.

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 : In a 6-pole wave wound dc machine the number of conductors is 70. The back pitch and commutator segments, respectively, are (A) 11and 35 (B) 12 and 34 (C) 13 and 35 (D) 14 and 34 

Description : A commutator with a diameter of 50 cm rotates at 1000 r.p.m. If brush width is 1.5 cm, the time of commutation will be (a) 0.168 m sec (b) 0.374 m sec (c) 0.481 m sec (d) 0.573 m sec

Description : The function of carbon brush and commutator arrangement in a d.c. motor is (a) to produce unidirectional torque. (b) to produce unidirectional current in the armature. (c) to help in changing the direction of rotation. (d) to reduce sparking. 

Description : The function of a brush and commutator arrangement in a dc motor is to  (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking

Answer : The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque

Description : Which of the following does not have a commutator? A) Dynamo B) Induction motor C) Universal motor D) None of these

Answer : Which of the following does not have a commutator? A) Dynamo B) Induction motor C) Universal motor D) None of these

Description : A commutator in a d.c. machine: (A) reduces power loss in armature (B) reduces power loss in field circuit (C) converts the induced a.c armature voltage into direct voltage (D) is not necessary

Answer : A commutator in a d.c. machine: converts the induced a.c armature voltage into direct voltage

Answer : To avoid formation of grooves in the commutator of a D.C. machine the brushes of opposite polarity should track each other.

Answer : In case of D.C. machine winding, number of commutator segments is equal to number of armature coils.

Answer : The insulating material used between the commutator segments is normally mica.

Answer : In a commutator mica is harder than copper.

Answer : Sparking at the commutator of a D.C. motor may result in damage to commutator segments, damage to commutator insulation, increased power consumption.

Description : Generally bearing bushes are made of (A) copper (B) white metal (C) gun metal (D) brass

Answer : Generally bearing bushes are made of brass

Description : The electrode of a direct are furnace is made of (1) Tungsten (2) Graphite (3) Silver (4) Copper 

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Answer : Permanent magnets are normally made of alnico alloys.

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Answer : Resistance wire is made up of Nichrome .

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Answer : Fine, dark particles, similar in size to smoke particles.  

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Answer : Ans: Monohybrid cross : Phenotypic ratio is 3:1 and Genotypic ratio 1:2:1. Dihybrid cross : Phenotypic ratio 9:3:3:1. Genotypic ratio is 1:2:2:4:1:2:1:2:1 

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