101) Which condition out of the five given below is not required for the build-up of a shunt generator?

  1. There must be sufficient residual magnetism in the poles
  2. For the given direction of rotation, shunt field coils should be correctly connected to the armature
  3. If excited on open circuit, the shunt field resistance should be more than the critical resistance
  4. Armature speed should be more than the critical speed
ANSWER
Answer: ( 4 )
EXPLANATION
No answer description required for this question.

102) A DC generator generates

  1. DC voltage
  2. AC voltage
  3. DC and AC voltage
  4. Pulsating DC
ANSWER
Answer: ( 2 )
EXPLANATION
A DC generator is an electrical machine which converts mechanical energy into electrical energy. The conversion to DC is performed by the commutator and brushes.

103) A DC generator can be termed as a

  1. Rotating amplifier
  2. Prime mover
  3. Power pump
  4. None of the above
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

104) Effect of armature flux on the main flux in a DC motor is that

  1. It makes distribution of the flux density across both sections unequal
  2. It inclines lines of force through the air gap such that they do not remain radial
  3. Both (1) and (2)
  4. None of these
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

105) For a series motor, field flux is

  1. Proportional to temperature
  2. Constant
  3. Proportional to armature current
  4. Inversely proportional to armature current
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

106) Field flux is constant in

  1. Compound motor
  2. Shunt motor
  3. Series motor
  4. None of the above
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

107) Function of the commutator in a DC machine is

  1. To change alternating voltage to direct voltage
  2. To change AC to DC
  3. To improve commutation
  4. For easy speed control
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

108) Dummy coil in a DC machine is used to

  1. For mechanical balance of armature
  2. Eliminate armature reaction
  3. Eliminate reactance voltage
  4. None of the above
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

109) If back e.m.f. suddenly disappears in a DC motor

  1. Motor will start action as a generator
  2. Motor will stop
  3. Winding will burn due to high armature current
  4. Nothing will happen
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

110) Torque-speed characteristic of a series motor is

  1. Parabola
  2. Rectangular hyperbola
  3. Linear
  4. None of the above
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

111) Direction of rotation of a DC series motor can be changed by interchanging

  1. Field terminals
  2. Voltage terminals
  3. Both (1) and (2)
  4. None of the above
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

112) Shunt motor has

  1. Low speed at high loads and high speed at low loads
  2. Low speed at low loads and high speed at low loads
  3. Widely varying speed
  4. Constant speed
ANSWER
Answer: ( 4 )
EXPLANATION
No answer description required for this question.

113) If a DC motor is connected across AC supply, the motor will

  1. Run at lower speed
  2. Burn
  3. Run at normal speed
  4. Run continuously but for sparking at brushes
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

114) If field current of a shunt motor is changed, then

  1. Torque remains constant but H.P will change
  2. H.P remains constant but torque will change
  3. Both remains constant
  4. Both will change
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

115) In series-parallel control method when two DC series motors are connected in series, speed of the set is

  1. Half of the speed of the motors
  2. Rated speed of any of the motors
  3. One-fourth of the speed of the motors
  4. Same as in parallel
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

116) The torque produced by a series combination of two DC series motor is

  1. Half the torque when they are connected in parallel
  2. Twice the torque when they are connected in parallel
  3. Four times the torque when they are connected in parallel
  4. Equal to the torque when they are connected in parallel
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

117) Synchronous reactance is defined as reactance

  1. Due to armature reaction and leakage of flux both
  2. Due to armature reaction of the machine
  3. Due to leakage flux
  4. Of synchronous machine
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

118) Armature winding of a series motor is excited

  1. Resistively
  2. Conductively
  3. Inductively
  4. None of the above
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

119) Speed of a DC motor depends upon

  1. Field flux
  2. Armature resistance
  3. Applied voltage
  4. All of the above
ANSWER
Answer: ( 4 )
EXPLANATION
No answer description required for this question.

120) Use of the starter in DC motors is necessary because

  1. They are not self-starting
  2. To light the high initial current by inserting high resistance
  3. To overcome back emf
  4. None of the above
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

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