DC machine MCQ #2

1) A motor converts
          A) Mechanical energy into electrical energy
          B) Chemical energy into electrical energy
          C) Electrical energy into Mechanical energy
          D) Electrical energy into chemical energy

2) No load speed of which of the following motor is highest?
          A) Differentially compound motor
          B) Cumulative compound motor
          C) Shunt Motor
          D) Series Motor

3) Which of the following rule is used to determine the direction of rotation of D.C motor?
          A) Fleming’s Left-hand Rule
          B) Coloumb’s Law
          C) Lenz’s Law
          D) Fleming’s Right-hand Rule

4) A three point starter is suitable for

          A) Shunt Motor

          B) Shunt & Compound Motor

          C) Series Motor

          D) Shunt, Series, and compound motor

5) Iron or magnetic losses are also called
          A) Core losses
          B) Field losses
          C) Copper losses
          D) Armature losses

6) D.C. generators are normally designed for maximum efficiency around
          A) full-load
          B) rated r.p.m.
          C) rated voltage
          D) all of the above

7) In a D.C. generator, the iron losses mainly take place in
          A) yoke
          B) commutator
          C) armature conductors
          D) armature rotor

8) By looking which particular part of the motor we can Identify a “DC motor”?
          A) Shaft
          B) Field winding
          C) Commutator
          D) Armature winding

9) The reason of using starter while starting of DC motor is
          A) To restrict armature current as there is no back E.M.F at starting
          B) Motors are not self-starting
          C) Restrict starting torque
          D) None of the above

10) If the flux per pole of a shunt-wound DC generator is halved, the generated e.m.f. at constant speed
          A) is doubled
          B) is halved
          C) remains the same
          D) None of the above

| (1)-C  | (2)-D  | (3)-A  | (4)-B  | (5)-A  | (6)-A  | (7)-D  | (8)-C  | (9)-A | (10)-B  |

11) The armature resistance of a DC motor is 0.5 , the supply voltage is 200V and the back e.m.f. is 196V at full speed. The armature current is:
          A) 4A
          B) 8A
          C) 400A
          D) 392A

12) According to Fleming’s left-hand rule if the forefinger points in the direction of the field than the middle finger will point in the direction of

          A) Current in the conductor

          B) Resultant force on the conductor

          C) Movement of the conductor

          D) None of the above

13)Which DC motor is used for conveyor?
          A) Series motor
          B) Cumulative compound motor
          C) Differentially compound motor
          D) Shunt motor

14) When the number of poles and number of armature conductor are fixed in D.C generator then which winding will give Higher EMF?
          A) Lap Winding
          B) Wave Winding
          C) Either Lap or Wave Winding
          D) Depend upon the conductor

15) When the speed of D.C motor is increased
          A)Back E.M.F increases and current drawn decreases
          B) Back E.M.F decreases and current drawn increases
          C) Back E.M.F and current drawn both increases
          D) Back E.M.F and current drawn both decreases

16)In case of 4 poles D.C Generator Provided with a two layer of Lap winding with sixteen coils, the pole pitch will be
          A) 32
          B) 16
          C) 8
          D) 4

17)  Sparking of commutator at D.C motor result in
          A) Increase in power consumption
          B) Damage to commutator insulation
          C) Damage of commutator segments
          D) All of the above

18) While applying Fleming’s Right – Hand Rule for finding the direction of induced emf, then thumb point towards
          A) Direction of motion of conductor if forefinger points in the direction of generated e.m.f
          B) Direction of induced e.m.f
          C) Direction of flux
          D) The direction of motion of conductor if forefinger point along the line of flux.

19)  Which DC motor is preferred for crane and hoist?
          A) Series motor
          B) Cumulative compound motor
          C) Shunt motor
          D) Differentially compound motor

20) What will happen if the 220 volts DC series motor is connected to 220 Volt Ac supply?
          A) The motor will not run
          B) The armature winding of the motor will burn
          C) The motor will run with less efficiency and more sparking
          D) Either 2 & 3


| (11)-B  | (12)-A  | (13)-A  | (14)-B  | (15)-A  | (16)- C | (17)-D | (18)-D  | (19)-A  | (20)-D |    

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