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### 25+ MCQ on DC Motor, Transformer, Induction Motor, Generator For RRB SSE Preparation

For cracking the cut off RRB  IOF Senior section or IOF engineers examination it is must to read all topics of exam syllabus. Here we will posting the 25+ Multiple choice question on Electrical Applications Devices Such as DC Motor, Transformer, Induction Motor With Answer Explained

## 25 + MCQ  ON DC MOTOR , TRANSFORMER, GENERATOR,

Q.1    The Transformer works on the principle                                                RRB JE RED SET 2014

A.  Mutual Induction     B.  Self Induction    C.  Electromechanical Conversion     D.  Both of A. and B.
Note- Actually transformer mainly works on mutual induction
Q.2   What will happen if we place Conventional transformer for DC purpose applications.
A. It get Destroy due to Excessive Resistance     B.  It get destroy due to less Resistance
C. It get destroy due to Excessive Impedance     D.  It get destroy due to less Impedance

Note- less will be the impedance high will be current hence Transformer Burns out.
Q.3   Which of the following parts of Transformer is responsible for carrying winding
IOF MECH SET 2014

A.  Core    B.   Limb   C.  Yoke   D.  Buchholz relay
Ans- B. Limb
Q.4 Which of the following parts of Transformer is responsible for Providing Horizontal path for carrying Flux
A.  Core    B.   Limb   C.  Yoke   D.  Buchholz relay
Ans- Yoke
Q.5  The EMF Developed in Transformer in any Windings is given by
A.   4.44 ∅_m  f N       B. 1.11 ∅_m  f BN     C. 4.44 ∅_m  If N      D.  1.11 ∅_m  If N
Where ∅_m=maximium flux ,  f=frequency , N=no.of turns in that windings ,  I=current
Ans- A.   4.44 ∅_m  f N
Q.6 Which of the following is the not a property of Ideal Transformer
A. has Zero losses              B.   Has zero resistance
C.  Leakage Flux is Zero    D. Permeability is Zero
Ans- D. Permeability is Zero
Q.7 Transformer is said to be Step down If
A.  No. Of turns in Primary Windings is less than that of Secondary
B.  Induced Current in Primary Windings is less than that of Secondary
C.   If Transformation Ratio is Greater than Unity
D. Induced Current in Primary Windings is Greater than that of Secondary
Ans- B. Induced Current in Primary Windings is less than that of Secondary

Q.8 at Ideal on load condition the Power Factor (cos∅) is –
A.  Lagging
C. Unity
D. Zero
Ans.  A. Lagging
Q.9 If the Ideal Transformer has Inductive load Then Magnetising Current is
A.  Lagging by 90 Degree
B. Leading by 90 Degree
C. Unity
D. Zero
Ans.  A Lagging by 90 Degree
Q.10 If the Ideal Transformer has capacitive load Then Magnetising Current is
A.  Lagging by 90 Degree
B. Leading by 90 Degree
C. Unity
D. Zero
Ans. B. Leading by 90 Degree
Q.11 If the Ideal Transformer has Resistive load Then Magnetising Current is
A.  Lagging by 90 Degree
B. Leading by 90 Degree
C. Unity
D. Zero
Ans- D. Zero
Note – Phase Difference in case of Resistive load is zero Whereas Power factor is Unity
Q.12 The magnetizing current drawn by transformers and induction motors is the cause for their
A. Zero Power Factor                                                                                                  RRB 2014 SSE Green Set
B. Leading Power factor
C. lagging P.F
D. Unity P.F
Ans- C. lagging P.F
Q.13 The O.C. (Open Circuit) Test in Transformer is performed for Determining
A.  Power Loss due to Soft Iron Core
B.  Power loss due to Copper windings
C. Power loss due to eddy currents
D. Both B. And C.
Ans- A.  Power Loss due to Soft Iron Core
Q.14 A Transformer Transforms                                                                  RRB 2014 JE RED SET
A. Frequency   B.  Voltage    C.  Current    D.  Both Voltage and Current
Ans.  D.
Q.15 the S.C. (Short Circuit) Test in Transformer is performed for Determining
A.  Power Loss due to Soft Iron Core
B.  Power loss due to Copper windings
C. Power loss due to eddy currents
D. Both B. And C.
Ans.  B.  Power loss due to Copper windings
Q.16 in performing the short circuit test of a transformer,                  RRB SSE GREEN SET 2014
A. The high voltage side is usually short circuited
B. The low voltage side short circuited
C. any side is short circuited with preference
D.  None of these
Ans- B. The low voltage side short circuited
Q.17 in Performing the O.C.  Test of a transformer,
A. The high voltage side is usually open circuited
B. The low voltage side open circuited
C. any side is open circuited with preference
D.  None of these
Ans. A. The high voltage side is usually open circuited
Q.18 The mechanical power developed by the armature of a d.c motor is equal to
A. The product of Back EMF and armature current                                              RRB SSE GREEN SET 2014
B. power input minus losses
C. product of power output and efficiency
D. power output plus iron losses
Ans A. The product of Back EMF and armature current
Q.19 The basic requirement of a D.C Armature winding is that it must be     RRB SSE GREEN SET 2014
A. Closed one   B. Lap winding   C.  Wave winding   D. Lap or wave winding
Ans. B. Lap Winding
Q.20. In the lap windings the number of parallel path is given by
A. No. Of Poles in motor
B. exactly Two
C. Depend upon the Voltage
D. none of these
Ans. A.  No. Of Poles in motor
Q.21 which of following part is not used in A.C. Power source        RRB SSE YELLOW SET 2014
A. commutator    B.  Carbon brush       C.  Slip rings       D. None of these
Ans- Commutator
Q.22 Which of the following types of motors has high starting Torque
A. Series motor
B. Differential Compound Motor
C. Shunt motor
D. None of these
Ans. A. Series motor but it is dangerous in no load condition
Q.23 In Rolling mills which of following motors is used
A. Series motor
B. Differential Compound Motor
C. Shunt motor
D. Cumulative Compound
Ans – D . Cumulative compound
Q.24 In Blowers, fans, lathe, drilling or milling machine the D.C. Motor used is
A. Shunt Motor
B. Series motor
C. Cumulative compound motor
D. Cumulative Compound motor
Ans. A. Shunt motor
Q.25 DC Series motors considered most suitable for the application in   RRB JE RED SET 2014
A. Fans          B.  Traction     C.   Water pumps    D. Flour Mills
Ans. Traction
Q.26 Carbon brushes are used in DC electric motors to                              RRB JE RED SET 2014
A. prevent sparking during commutation
B. Provide a path for flow of current
C. brush off carbon deposits on the commutator
D. none of these
Ans - A and B both but mainly B. Provide a path for flow of current
Q.27 The frequency of emf generated by a generator depends upon its  RRB JE RED SET 2014

A.    Speed                B. No. Of poles         C.   Both A and B          D. None of these
Ans- C. Both A and B