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# MCQ in AC Motors Part 5 | REE Board Exam

This is the Multiple Choice Questions Part 5 of the Series in AC Motors as one of the Electrical Engineering topic. In Preparation for the REE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electrical Engineering field, Electrical Engineering Books, Journals and other Electrical Engineering References.

#### Continue Practice Exam Test Questions Part 5 of the Series

Choose the letter of the best answer in each questions.

201.ย  A 3ฮฆ, induction motor is wound for 4 poles and is supplied from a 50 Hz system. What is the rotor frequency when rotor runs at 1410 rpm?

A.ย  3 Hz

B.ย  2.5 Hz

C.ย  2.9 Hz

D.ย  3.5 Hz

Solution:

SINGLE PHASE MOTORS

202.ย  Most of single-phase induction motors are ____ machines.

A.ย  2 pole

B.ย  6 pole

C.ย  8 pole

D.ย  4 pole

Solution:

203.ย  The main winding and starting winding of a single -phase induction motor are connected in ____ across the supply.

A.ย  series

B.ย  parallel

C.ย  series-parallel

D.ย  none of these

Solution:

204.ย  The starting winding of a single-phase induction motor has ____ that of the main winding.

A.ย  more poles than

B.ย  less poles than

C.ย  same number of poles

D.ย  none of these

Solution:

205.ย  A 50 Hz, 4 pole single-phase induction motor will have a synchronous speed of

A.ย  1500 rpm

B.ย  750 rpm

C.ย  1200 rpm

D.ย  none of these

Solution:

206.ย  A 4 pole, 50 Hz single-phase induction motor has a slip of 5%. The speed of the motor will be

A.ย  1500 rpm

B.ย  1425 rpm

C.ย  1200 rpm

D.ย  none of these

Solution:

207.ย  In a single-phase induction motor, speed sensitive centrifugal switch is connected in ____ winding.

A.ย  parallel with main

B.ย  series with main

C.ย  series with starting

D.ย  parallel with starting

Solution:

208.ย  The purpose of starting winding in a singlephase induction motor is to

A.ย  reduce losses

B.ย  limit temperature rise of the machine

C.ย  produce rotating flux in conjunction with main winding

D.ย  none of these

Solution:

209.ย  If Im and Is are the current in the main and starting windings respectively and ฮฑ is the angle between Im and Is, then motor torque T is given by

A.ย  T ฮฑ Im Is cos ฮฑ

B.ย  T ฮฑ Im Is sin ฮฑ

C.ย  T ฮฑ Im Is

D.ย  none of these

Solution:

210.ย  In the resistance split-phase induction motor shown in Fig. 1, the angle ฮฑ between Im and Is is about

A.ย  80 degrees

B.ย  65 degrees

C.ย  75 degrees

D.ย  25 degrees

Solution:

211.ย  The starting winding of a split-phase induction motor shown in Fig. 1 is disconnected when the motor attains about ____ of synchronous speed.

A.ย  75%

B.ย  50%

C.ย  25%

D.ย  100%

Solution:

212.ย  In the resistance split-phase induction motor shown in Fig. 1, the main windings has

A.ย  high resistance and high inductance

B.ย  high resistance and low inductance

C.ย  low resistance and high inductance

D.ย  low resistance and low inductance

Solution:

213.ย  At starting, the current Is in the starting winding shown in Fig. 1

A.ย  lags V by 90 degrees

B.ย  leads V by 90 degrees

C.ย  is nearly in phase with V

D.ย  leads V by 75 degrees

Solution:

214.ย  A resistance split-phase induction motor is used for

D.ย  none of these

Solution:

215.ย  The direction of split-phase induction motor can be reversed by interchanging the connections of supply of

A.ย  either main or starting winding

B.ย  both main and starting winding

C.ย  rotor winding

D.ย  none of these

Solution:

216.ย  The resistance split-phase induction motor has ____ starting torque.

A.ย  high

B.ย  moderate

C.ย  very low

D.ย  none of these

Solution:

217.ย  The resistance split-phase induction motor is used in those applications where

A.ย  starting is frequent

B.ย  starting period is long

C.ย  starting is infrequent

D.ย  none of these

Solution:

218.ย  The resistance split-phase induction motors are the most popular single-phase induction motors because of

A.ย  their low cost

B.ย  their high starting torque

C.ย  the long starting period

D.ย  none of these

Solution:

219.ย  In the capacitor start induction motor shown in Fig. 2, the angle ฮฑ between Im and Is is

A.ย  exactly 90ยฐ

Solution:

220.ย  The value of Is in capacitor-start motor shown in Fig. 2 is ____ the current Im.

A.ย  equal to

B.ย  less than that of

C.ย  more than that of

D.ย  none of these

Solution:

221.ย  The capacitor C used in the capacitor-start motor shown in Fig. 2 is always a ____ capacitor.

A.ย  paper

B.ย  ceramic

C.ย  mica

D.ย  electrolytic

Solution:

222.ย  At starting, the line current of a capacitor-start induction motor is ____ normal full-load current.

A.ย  8 to 10 times

B.ย  4 to 5 times

C.ย  equal to

D.ย  7 to 8 times

Solution:

223.ย  In a capacitor-start, capacitor-run motor, ____ winding is cut-out after starting.

A.ย  starting

B.ย  main

C.ย  neither A or B

D.ย  none of these

Solution:

224.ย  A capacitor-start, capacitor-run motor has

A.ย  low power factor

B.ย  high power factor

C.ย  low efficiency

D.ย  high starting torque

Solution:

225.ย  The capacitor-start, capacitor-run induction motor acts as a true 2-phase motor at

A.ย  starting

Solution:

226.ย  The capacitor-start, capacitor-run motor is used in those applications where

A.ย  highly starting torque is required

B.ย  silence is important

C.ย  noisy operation is not important

D.ย  none of these

Solution:

227.ย  The capacitor-start, capacitor-run motor has

A.ย  no centrifugal switch

B.ย  low power factor

C.ย  noisy operation

D.ย  low efficiency

Solution:

228.ย  Capacitor motors ____ resistance split-phase induction motors.

A.ย  are costlier than

B.ย  are less costly than

C.ย  cost about the same as

D.ย  poor starting torque than

Solution:

229.ย  Most of the troubles of single-phase induction motor are traceable to the

A.ย  rotor bars

B.ย  main winding

C.ย  shaft bearings

D.ย  starting switch

Solution:

230.ย  The single-phase shaded pole motor has

A.ย  squirrel cage rotor

B.ย  wound rotor

C.ย  high power factor

D.ย  high starting torque

Solution:

231.ย  The direction of rotation of shaded pole motor depends upon

A.ย  supply frequency

B.ย  number of poles on the stator

C.ย  which half of the pole is shaded

D.ย  supply voltage

Solution:

A.ย  70 to 80%

B.ย  60 to 70%

C.ย  30 to 35%

D.ย  5 to 10%

Solution:

233.ย  The single-phase series motor can operate on

A.ย  ac only

B.ย  dc only

C.ย  both ac and dc

D.ย  none of these

Solution:

234.ย  For the same rating, a dc series motor costs _____ single phase series motor.

B.ย  more than

C.ย  less than

D.ย  none of these

Solution:

235.ย  A 2 HP dc series motor will weigh ___ 2 HP single-phase series motor.

B.ย  less than

C.ย  more than

D.ย  none of these

Solution:

236.ย  A vacuum cleaner employs ____ motor.

A.ย  resistance split-phase

B.ย  capacitor start

D.ย  single-phase series

Solution:

237.ย  The best suited motor to drive a 1/4 HP fan in a hospital would be ____ motor.

B.ย  single-phase series

C.ย  capacitor run

D.ย  hysteresis

Solution:

238.ย  The washing machine generally employs ____ motor.

A.ย  single-phase series motor

B.ย  resistance split-phase

D.ย  hysteresis

Solution:

239.ย  The best suited motor to drive a 3/4 HP air compressor would be ____ motor.

A.ย  capacitor start

B.ย  single-phase series

D.ย  resistance split-phase

Solution:

240.ย  The least expensive fractional horsepower motor is

B.ย  capacitor-start

C.ย  split phase

D.ย  ac series

Solution:

241.ย  The starting winding of a single-phase motor is placed in the

A.ย  rotor

B.ย  stator

C.ย  armature

D.ย  field

Solution:

242.ย  One of the characteristics of a single-phase motor is that it

A.ย  is self-starting

B.ย  is not self-starting

C.ย  requires only one winding

D.ย  can rotate in one direction only

Solution:

243.ย  After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on ____ winding.

A.ย  rotor

B.ย  field

C.ย  compensating

D.ย  running

Solution:

244.ย  If starting winding of a single-phase induction motor is left in the circuit, it will

A.ย  draw excessive current and overheat

B.ย  run slower

C.ย  run faster

Solution:

245.ย  The direction of rotation of a single-phase motor can be reversed by

A.ย  reversing connections of both windings

B.ย  reversing connections of starting winding

C.ย  using a reversing switch

D.ย  reversing supply connections

Solution:

246.ย  If a single-phase induction motor runs slower than normal, the more likely defect is

A.ย  improper fuses

B.ย  shorted running winding

C.ย  open starting winding

D.ย  worn bearing

Solution:

247.ย  The capacitor in a capacitor-start induction run ac motor is connected in series with ____ winding.

A.ย  starting

B.ย  squirrel-cage

C.ย  running

D.ย  compensating

Solution:

248.ย  A permanent-split single-phase capacitor motor does not have

A.ย  centrifugal switch

B.ย  starting winding

C.ย  squirrel-cage rotor

D.ย  high power factor

Solution:

249.ย  The starting torque of a capacitor-start induction-run motor is directly related to the angle or between its two winding currents by the relation

A.ย  cos

B.ย  sin

C.ย  tan

D.ย  sin /2

Solution:

250.ย  In a two-value capacitor motor, the capacitor used for running purposes is a/an

A.ย  dry-type ac electrolytic capacitor

B.ย  paper-spaced oil filled type

C.ย  air-capacitor

D.ย  ceramic type

Solution:

#### Questions and Answers in AC Motors

Following is the list of practice exam test questions in this brand new series:

MCQ in AC Motors
PART 1: MCQ from Number 1 โ 50                Answer key: included
PART 2: MCQ from Number 51 โ 100            Answer key: included
PART 3: MCQ from Number 101 โ 150           Answer key: included
PART 4: MCQ from Number 151 โ 200           Answer key: included
PART 5: MCQ from Number 201 โ 250           Answer key: included
PART 6: MCQ from Number 251 โ 300           Answer key: included
PART 7: MCQ from Number 301 โ 350           Answer key: included
PART 8: MCQ from Number 351 โ 400            Answer key: included
PART 9: MCQ from Number 401 โ 450            Answer key: included
PART 10: MCQ from Number 451 โ 500          Answer key: included

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