Technical note 1: DC Motor MCQ1

1    No-load speed of which of the following motor will be highest ?
(a)     Shunt motor    
(b)     Series motor
(c)    Cumulative compound motor
(d)    Differentiate compound motor
Ans: b
2.    The direction of rotation of a D.C. series motor can be changed by
(a)     interchanging supply terminals
(b)     interchanging field terminals
(c)    either of (a) and (b) above
(d)    None of the above
Ans: b
3.    If a D.C. motor is to be selected for conveyors, which motor would be preferred ?
(a)  Series motor
(b)  Shunt motor
(c)  Deferentially compound motor
(d)  Cumulative compound motor
Ans: a
4 Which D.C. motor will be preferred for machine tools ?
(a)    Series motor
(b)    Shunt motor   
(c)    Cumulative compound motor
(d)    Differential compound motor
Ans: b
5..    Which D.C. motor is preferred for elevators ?
(a)    Shunt motor
(b)    Series motor
(c)    Differential compound motor
(d)    Cumulative compound motor
Ans: d
6    According to Fleming's left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of
(a)     current in the conductor 
(c)    resultant force on conductor
(d)    none of the above
Ans: a
7.What will happen, with the increase in speed of a DC motor?
a) Back emf increase but line current falls.
b) Back emf falls and line current increase.
c) Both back emf as well as line current increase.
d) Both back emf as well as line current fall.
Ans: a
8 Direction of rotation of motor is determined by ____________
a) Faraday’s law
b) Lenz’s law
c) Coulomb’s law
d) Fleming’s left-hand rule

Ans: d

9 The armature of DC machine is made up of laminated sheets to .......

  a).Reduce hysteresis loss

   b).Reduce the eddy-current loss

   c).Reduce armature copper loss

   d).Increase dissipation of heat from the armature surface

Ans:b

10 The function of a brush and commutator arrangement in a DC motor is .......

   a)To produce unidirectional torque

   b)To produce unidirectional current in the armature

   c)To help in changing the direction of rotation of the armature

   d)To reduce sparking

Ans:a