1030233110 Electrical Machines – I (Theory ) MCQ QUESTIONS WITH ANSWERS

 

 

ELECTRICAL MACHINES I - 20 MARKS MCQ TEST LINK MCQ TEST LINK

 

1030233110 Electrical Machines – I (Theory)

PART – A ( ONE MARKS )

1.      The main principle of operation of a DC machine is based on:
 a) Faraday’s laws of electromagnetic induction
b) Coulomb’s law
c) Lenz’s law
d) Kirchhoff’s law

 

2.      The function of a commutator in a DC machine is to:
a) Convert AC to DC
b) Convert DC to AC
 c) Reverse current direction
d) Supply excitation

 

3.      The armature core in a DC machine is laminated to:
 a) Reduce eddy current loss
b) Reduce hysteresis loss
c) Increase flux
d) Reduce copper loss

 

4.      The field winding of a shunt generator is connected:
 a) In parallel with armature
b) In series with armature
c) Across the commutator
d) To load

 

5.      In a transformer, the core is made of:
 a) Silicon steel
b) Cast iron
c) Aluminium
d) Brass

 

6.      The EMF equation of a transformer is:
 a) 4.44 f N Φm
b) 2.22 f N Φm
c) 4.44 N Φm
d) 2.22 N Φm

 

7.      The losses in a transformer are:
 a) Iron and copper losses
b) Friction losses
c) Windage losses
d) Mechanical losses

 

 

8.      Efficiency of a transformer is maximum when:
 a) Iron loss = Copper loss
b) Iron loss > Copper loss
c) Iron loss < Copper loss
d) Load is full

 

9.      The torque developed in a DC motor depends on:
 a) Flux and armature current
b) Speed and voltage
c) Resistance and current
d) Load and efficiency

 

10.  The back EMF in a DC motor opposes:
 a) The applied voltage
b) The armature current
c) The field current
d) The load torque

 

11.  The speed of a DC shunt motor is nearly:
 a) Constant
b) Zero
c) Variable
d) Inversely proportional to voltage

 

12.  The function of the starter in a DC motor is to:
 a) Limit starting current
b) Increase torque
c) Increase speed
d) Control voltage

 

13.  Which type of three-phase transformer connection is best suited for stepping up voltage at power generation stations?
a) Star–Star (Y–Y)
b) Delta–Delta (Δ–Δ)
c) Star–Delta (Y–Δ)
 d) Delta–Star (Δ–Y)

 

14.  What is the primary purpose of a Buchholz relay in a transformer?
a) Regulating voltage
b) Cooling the transformer
 c) Detecting internal faults
d) Measuring oil level

 

15.  Which cooling method in transformers uses radiators and fans for heat dissipation?
a) ONAN
 b) ONAF
c) OFAF
d) OFWF

 

16.  In a transformer, ON-load tap changers are used to:
a) Cool the transformer during heavy load
 b) Adjust the voltage without interrupting supply
c) Change phase sequence
d) Disconnect the transformer from load

 

17.  What is the main purpose of preventive maintenance in electrical machines?
a) To repair after breakdown
b) To ensure regular machine downtime
 c) To prevent unexpected failures and extend equipment life
d) To increase the noise level

 

18.  A common cause of sparking at the commutator in a DC machine is:
a) Low field resistance
b) Proper brush alignment
c) Overheating of the rotor shaft
 d) Worn-out or misaligned brushes

 

19.  The Breakdown Voltage (BDV) test on transformer oil is used to measure:
a) Oil temperature
b) Oil viscosity
 c) Dielectric strength of the oil
d) Oil volume

 

20.  Which instrument is commonly used to measure earth resistance in electrical installations?
a) Megger
b) Clamp meter
 c) Earth tester
d) Multimeter