1. . An electrical motor is a machine which converts;
(A) Electrical energy into chemical energy
(B) Chemical energy into electrical energy
(C) Mechanical energy into electrical energy
(D) Electrical energy into mechanical energy
2. . The construction of d.c motor is;
(A) same as a.c motor
(B) different to d.c. generator
(C) same as d.c. generator
(D) same as transformer
3. . The DC motor can be identified by looking at this part;
(A) Armature
(B) Commutator
(C) Stator
(D) Carbon brushes
4. . The mechanical force developed by a d.c. motor is given by;
(A) B l V
(B) B I L
(C) N 𝑑𝜙/𝑑𝑡
(D) 𝜙 Z N / 60
5. . The direction of mechanical force produced in a DC motor can be determined by;
(A) Faraday’s Law
(B) Fleming’s Left-Hand Rule
(C) Coulomb’s Law
(D) Lenz’s Law
6. . Fleming’s left-hand rule is used for;
(A) D.C. motor
(B) D.C. generator
(C) Rectifier
(D) All of these
7. . The speed of d.c. motor is directly proportional to;
(A) Flux
(B) Back e.m.f.
(C) No. of poles
(D) All of these
8. . Back e.m.f. is induced in;
(A) Armature
(B) Series field
(C) Commutator
(D) Shunt field
9. . At the time of starting, the back e.m.f. of d.c. motor is;
(A) Zero
(B) Low
(C) High
(D) Very high
10. . Back e.m.f. of d.c. motor;
(A) does not depend upon applied voltage
(B) is always greater than applied voltage
(C) is always opposite to applied voltage
(D) is always zero
11. . The formula to find back e.m.f. of d.c. motor is;
(A) V + IaRa
(B) V - IshRsh
(C) IaRa
(D) V - IaRa
12. . At the time of starting, the current of d.c. motor is high because of;
(A) Eb = V
(B) Eb > V
(C) Eb < V
(D) Eb = 0
13. . Back e.m.f. of d.c. motor depends upon;
(A) All of these
(B) Flux per pole
(C) Parallel paths of current
(D) Speed of motor
14. . In the presence of back e.m.f., motor current will be;
(A) Zero
(B) Normal
(C) Very high
(D) Very low
15. . The back e.m.f. of a d.c. motor;
(A) often exceeds the supply voltage
(B) aids the applied voltage
(C) regulates its armature voltage
(D) helps in energy conversion
16. . If the speed of d.c. motor is decreased, armature current will be;
(A) decreased
(B) increased
(C) zero
(D) remain constant
17. . A d.c. motor can be used as;
(A) Amplifier
(B) Cycloconverter
(C) Prime mover
(D) Rectifier
18. . In a d.c. motor, unidirectional torque is produced with the help of;
(A) Both (a) and (b)
(B) Commutator
(C) End plates
(D) Brushes
19. . Formula to obtain armature current of d.c. motor is;
(A) (V + Eb)/Ra
(B) (V − Eb)/Ra
(C) (V + Eb)/(Ra + Rsh)
(D) V/Ra
20. . The current drawn by a 120V d.c. motor of armature resistance 0.5Ω and back e.m.f. 110 V is .......... ampere.
(A) 220
(B) 240
(C) 20
(D) 5