Monday 10 June 2013

KSEB sub engineer kpsc 2012 sample question 2



                                                                                                                                                                                        

116.     A synchronous machine has its field winding on the stator and armature winding on the rotor. Under steady running condition, the air gap field
(a)  rotates at synchronous speed w.r.t. rotor
(b) rotates at synchronous speed in the direction ofrotation of the rotor
(c) remains stationary w.r.t. stator                    (cl)     remains stationary w.r.t. rotor.
117.     In a pure LC parallel circuit under resonance condition, current drawn from the supply mains is


(a) very large
(c) V/./LC,


(b) vJLC
(d) Zero.


118.     In a circuit the voltage and current are given by V = (10 + j5) and i = (6 + j4). The circuit

IS

(a) inductive
(b) capacitive
(c) resistive
(d) it could be any of the above.
119.
The power in the circuit of problem 118 is
(a) 60 watt

(b) 20 watt

(c) 80 watt
(d) 70 watt.
120.         The reactive power in the circuit of problem 1 18 is
(a)     70 V Ars                                               (b) 60 V Ars
(c) 10 V Ars                                              (d) - 10 V Ars.
121.         The current at a given point in a certain circuit may be given a function of time as


i(t)


= - 3 + t


The total charge passing the point between t = 99 sec and t = 102 sec is
(a) 112 C                                                    (b) 242.5 C
(c) 292.5 C                                                 (d) 345.6 C.
122.         An alternator has a phase sequence of RYB for its phase voltages. In case the field current is reversed, the phase sequence will become


(a)    RBY
(c) YRB


(b) RYB
(d) None of the ahove.


123.         An alternator has a phase sequence of RYB for its phase voltage. In case the direction of rotation of alternator is reversed, the phase sequence will become


(a)   RBY
(c) YRB


(b) RYB
(d) None of the above.


124.         Modern high speed synchronous generator used in thermal plants have
(a)    salient pole rotors                                 (b) cylindrical rotor
(c) either salient or cylindrical                      (d) spherical rotor.
125.         In a split phase 1-phase induction motor the wire of the main winding as compared to auxiliary  winding  is
(a)    thinner                                                 (b) thicker
(c) same size                                               (d) could be either way.










126.         The rotor of a 1-phase induction motor is
(a)    a cage or wound rotor
(c) always a wound rotor





(b) always a cage rotor
(d) a double cage rotor.


127.         In a capacitor start motor, the capacitor is connected


(a)    in series with the main winding
(c) in parallel with the auxiliary winding
128.    A ceiling fan uses
(a)    split phase motor
(c) capacitor start motor
129.         A two-phase servo-motor has
(a)    wound rotor
(c) wound or cage rotor
130.         The motor used in electric toys is
(a)    split phase motor
(c) shaded pole motor


(b) in series with the auxiliary winding
(d) in series with both the windings.


(b) capacitor start capacitor run motor
(d) universal motor.


(b) cage rotor
(d) double cage rotor.


(b) permanent capacitor motor
(d) capacitor start motor.


131.         The voltage fed to the two windings of a two-phase servo motor must be
(a)    in phase with each other                             (b) goo apart with each other
(c) 180° apart with each other
(d) more than goo but less than 180° apart with each other.
132.         A stepper motor is a


(a)    de motor
(c) two-phase motor


(b) single phase ac motor
(d) multi-phase motor.


133.         Phantom loading heat run test on transformers is performed by means of
(a)    S.C. Test                                               (b) O.C. Test
(c) Half time on S.C. and halftime on D.C. test
(d) Sumpner's Test.
3
134.         A power transformer has its maximum efficiency at 4 th full load. Its iron loss and full

load copper loss Pc are related as
16
(a)    P/Pc = g


4
 
(c) P/Pc = 3

135.         In case of a transformer the low voltage winding is placed near the core because
(a)    it reduces insulation requirement                  (b) it reduces hysteresis loss
(c) it is convenient                                      (d) it reduces eddy current loss.











136.         Conservator on a transformer is provided to
(i)  prevent oil from coming in contact with the atmosphere
(ii)   allow breathing and to increase the oil surface exposed to atmosphere
(iii)    allow breathing and also to reduce the oil surface exposed to atmosphere.
Tick out the correct answer
(a) only (i) is true                                            (b) only (ii) is correct
(c) only (iii) is correct                                      (d) (i) (ii) (iii) all are correct.
137.        Two transformers connected in parallel share loads in the ratio of their KVA ratings pro­ vided their impedances are


(a)    in inverse ratio oftheir ratings
(c) equal


(b) in direct ratio of their ratings
(d) none of the above is necessary.


138.         A transformer is operating under no load condition at rated voltage. A small air gap is now cut  across the yoke of its core. The maximum flux density and magnetising current respectively.
(a)    decrease and decrease                              (b) decrease and increase
(c) increase and increase                                  (d) remain same and increase.
139.         A 440/220 V transformer has per unit impedance of 0. 1  In order to circulate full load current during shot circuit the voltage impressed on high voltage side is


(a)    22 V
(c) 44 volt


(b) 10 v
(d) 20 volt.


140.         For fixed primary voltage and secondary load current if the p.f. of the load is changed from
0.6 lead to 0.8 lead, the secondary voltage
(a) increases                                                 (b) decreases
(c) first decreases and then increases                  (d) does not change.
141.         A transformer has maximum efficiency at full load. Its all day efficiency will be maximum when it is operated
(a)    full load all the time
3
(b)  full load half the time and 4th load half time

(c)   full load and halfload each half the time
(d)   full load half time and no load half the time
142.         Inter poles help commutation in a de machine by
(a)    aiding the main poles
(b)   causing dynamically induced e.m.f. in the coils undergoing commutation
(c)   causing statically induced e.m.f. in the coils undergoing commutation
(d)   cancelling the armature reaction m.m.f.
143.         If the armature current if a.d.c. motor is increased keeping the field flux constant, the torque developed


(a)   increases proportionally
(c) increases proportional to F


(b) decreases in inverse ratio
(d) remains constant.







144.         The critical field resistance of a.d.c. shunt generator is
(a)    the value of field circuit resistance above which the generator would fail to excited
(b)   the value of field circuit resistance below which this generator would fail to excite
(c)   the resistance of the field winding                  (d) none of the above.
145.         For a.d.c. shunt generator, the critical resistances are for
(a)    load circuit only                                       (b) field circuit only
(c) load and field circuits                                  (d) none of the two circuits.
146.         In Hopkinson's test on two identical d.c. machines the power input to the armature circuit consists of
(a)    rated power of the two machines
(b)   copper loss + no load iron loss + windage and friction loss + stray load loss
(c)   armature copper loss + no load iron loss + stray load loss
(d)   armature copper loss + no load iron loss + windage and friction loss
147.         Two coupled d.c. series motors with constant torque load are changed over from series to parallel connection across a fixed voltage supply. The speed of the combined set as com­ pared to original speed becomes
(a)    Twice                                                   (b) Half
(c) -J2 times                                               (d) no change.
148.         A d.c. machine has maximum efficiency when
(a)    iron losses equal copper losses                     (b) constant losses equal variable losses
(c)   windage and friction losses equal copper losses
(d)   (a) and (b).
149.         The d.c. generator used for voltage boost is
(a)    shunt                                                    (b) series
(c) separately excited                                     (d) compound.
150.        In a level compound generator the terminal voltage at half load as compared to no load is
(a)    more                                                    (b) less
(c) same                                                    (d) none ofthe above is necessary.
                                                                                                                                                                         


Answers:


l16. (c)
l1 7. (d)
l18. (b)
l19. (c)
120. (d)
121.
(c)
122. (b)
123. (a)
124.  (b)
125. (b)
126. (b)
127.
(b)
128. (c)
129. (b)
130. (c)
131. (b)
132. (d).
133.
(d)
134. (d)
135.  (a)
136. (c)
137. (a)
138. (d)
139.
(c)
140. (b)
141. (a)
142.  (b)
143. (a)
144. (a)
145.
(c)
146. (b)
147. (a)
148. (b)
149. (b)
150. (a)

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