## electrician

### MCQ ON DC MOTOR PAGE - 1

1.
 A force will act  on a conductor placed in a magnetic field when A A current is flowing in the conductor B The conductor is rotating C The conductor is placed in the magnetic field and it is not carrying a current D It is placed at right angle to the field Answer : A Explanation :
2.
 The back e.m.f opposes A Current B Applied e.m.f C Torque D Terminal voltage Answer : B Explanation :
3.
 Back e.m.f is developed in the armature due to A Current B Supply voltage C Intersection of the magnetic flux by the armature conductors D Interaction of the two magnetic field Answer : C Explanation :
4.
 The magnitude of Eb in a.d.c motor in the start is equal to A Zero B Applied e.m.f. C More than applied e.m.f D Maximum Answer : A Explanation :
5.
 If in a shunt motor the applied emf is kept constant then on increasing the load, the shunt filed strength will become_____its normal value A Less than B More than C Equal to D Zero Answer : C Explanation :
6.
 In a series motor, the magnetic field flux stands A Proportional to armature current B Equal to armature current C Inversely proportional to armature current D Constant Answer : A Explanation :
7.
 The speed of a series motor is very high at no load because in  such state A Back emf is larger B Armature voltage is lesser C Flux is very low D Armature current is very low Answer : C Explanation :
8.
 A series motor is wound with A Find wire winding B Nichrome wire winding C Thick wire winding D Double wire winding Answer : C Explanation :
9.
 In a shunt motor, a starter is used for A Speed control B Back e.m.f control C Applied e.m.f control D Current control in the start Answer : D Explanation :
10.
 Voltage equation for a d.c motor is A V=Eb+Ia.Ra B V=Eb-Ia.Ra C V=V+Ia.Ra D V=V-Ia.Ra Answer : A Explanation :
11.
 The rotating part of ad.c motor is known as A Pole B Stator C Rotor D Armature Answer : D Explanation :
12.
 In a d.c machine, a dummy coil is used to A eliminate reactance voltage B eliminate armature reaction C create a mechanical balance in the armature D eliminate vibrations of the machine Answer : C Explanation :
13.
 The rotational speed of a d.c shunt motor can be increases above its full speed by A Increasing the armature current B Decreasing the armature current C Increasing the field current D Decreasing the filed current Answer : D Explanation :
14.
 On increasing the load of a d.c shunt motor, its speed will A Remain constant B Increase proportionately C Increase slightly D Reduce slightly Answer : D Explanation :
15.
 The armature current (Ia) drawn by a d.c motor is proportional to A The applied emf B The torque required C The flux required D The speed of the motor Answer : B Explanation :
16.
 The power written on the name plate of a a d.c. motor is always A The power drawn in KVA B The power drawn in kW C The output power available at the shaft D The gross power Answer : C Explanation :
17.
 The efficiency of an electrical machine  will be high if A Its losses are minimum B Its current drainage is minimum C The applied e.m.f is minimum D The load is minimum Answer : A Explanation :
18.
 The direction of rotation of a d.c motor can be reversed by A Reversing the supply connections B Interchanging the armature and filed connections C Adding a resistance in the filed circuit D Reversing the armature connections or the filed connections Answer : D Explanation :
19.
 Reversing the armature connections or the filed connections A Zero B 3000 r.p.m C 3600 rpm D Infinity Answer : D Explanation :
20.
 if the back e.m.f is absent in a d.c. motor  then the A motor will run at a very high speed B motor will run at a very low speed C motor will burn D motor will not run at all Answer : C Explanation :