1. . The induced e.m.f. by electromagnetic induction is firstly stated by the scientist:
(A) Heinrich Lenz
(B) Michael Faraday
(C) Charles Augustin De-Coulomb
(D) Joseph Henry
2. . Whenever a conductor or a coil cuts the magnetic flux, an e.m.f is induced in that conductor or coil, this is called:
(A) Joule’s Law
(B) Lenz’s Law
(C) Faraday’s Law
(D) Coulomb’s Law
3. . The relationship between the magnitude of induced e.m.f. and rate of change of flux linkage is:
(A) Directly proportional
(B) Directly proportional to square
(C) Inversely proportional
(D) Inversely proportional to square
4. . According to Faraday’s laws of electromagnetic induction, the induced e.m.f. is:
(A) N dϕ/dt
(B) N dϕ/dt
(C) N dϕ·dt
(D) N + dϕ/dt
5. . The unit of magnetic flux is:
(A) Weber
(B) Henry
(C) Coulomb
(D) Wb/m²
6. . The working principle of d.c. generator is:
(A) Faraday’s Electromagnetic Induction Law
(B) Lenz’s law
(C) Fleming’s right hand rule
(D) Coulomb’s Law
7. . When a conductor cuts the stationary magnetic field by movement, then induced e.m.f is called:
(A) Statically induced e.m.f.
(B) Mechanically induced e.m.f.
(C) Magnetically induced e.m.f.
(D) Dynamically induced e.m.f.
8. . When magnetic field moves and cuts by stationary conductor, then induced e.m.f. is called:
(A) Statically induced e.m.f.
(B) Dynamically induced e.m.f.
(C) Magnetically induced e.m.f.
(D) Mechanically induced e.m.f.
9. . The induced e.m.f. in a DC generator is:
(A) Statically induced e.m.f.
(B) Mechanically induced e.m.f.
(C) Magnetically induced e.m.f.
(D) Dynamically induced e.m.f.
10. . The induced e.m.f. in an AC generator is:
(A) Dynamically induced e.m.f.
(B) Statically induced e.m.f.
(C) Magnetically induced e.m.f.
(D) Mechanically induced e.m.f.
11. . When the conductor and electromagnet are stationary but the magnetic field is changed, then induced e.m.f. is called:
(A) Dynamically induced e.m.f.
(B) Statically induced e.m.f.
(C) Magnetically induced e.m.f.
(D) Mechanically induced e.m.f.
12. . The induced e.m.f. in a transformer is:
(A) Statically induced e.m.f.
(B) Dynamically induced e.m.f.
(C) Magnetically induced e.m.f.
(D) Mechanically induced e.m.f.
13. . Self-induced e.m.f. =
(A) L dϕ/dt
(B) N dϕ/dt
(C) N di/dt
(D) L di/dt
14. . The induced e.m.f. by electromagnetic induction depends upon:
(A) All of these
(B) Length of conductor
(C) Relative motion between conductor and magnetic field
(D) Strength of magnetic field
15. . According to Fleming’s right hand rule (& left-hand rule), the first finger points:
(A) Direction of magnetic field
(B) Movement of conductor
(C) Direction of current
(D) None of these
16. . According to Fleming’s right hand rule (& left-hand rule), the middle finger points:
(A) Movement of conductor
(B) Direction of magnetic field
(C) None of these
(D) Direction of current
17. . According to Fleming’s right hand rule (& left-hand rule), the thumb points:
(A) Movement of conductor
(B) Direction of magnetic field
(C) Direction of current
(D) None of these
18. . Fleming’s right hand rule is used for:
(A) Synchronous Motor
(B) D.C. Motor
(C) Transformer
(D) D.C. Generator
19. . Fleming’s left-hand rule is used for:
(A) D.C. Generator
(B) Synchronous Motor
(C) Transformer
(D) D.C. Motor
20. . Induced effect always opposes the cause that produced it is called:
(A) Joule’s Law
(B) Faraday’s Law
(C) Lenz’s Law
(D) Coulomb’s Law
21. . When a current carrying conductor is placed in magnetic field then a mechanical force acts in a direction of:
(A) Both (a) and (b)
(B) Perpendicular to magnetic field
(C) Parallel to magnetic field
(D) Perpendicular to current
22. . Mechanical force on a current carrying conductor in a magnetic field is given by:
(A) L di/dt
(B) N dϕ/dt
(C) BIl
(D) BlV
23. . If a current carrying conductor is at right angles to the magnetic field, then force ‘F’ is:
(A) BIl sinϕ
(B) Zero
(C) Near to zero
(D) Maximum
24. . If a current carrying conductor is parallel to the magnetic field, then force ‘F’ is:
(A) Maximum
(B) Zero
(C) Near to zero
(D) BIl sinϕ
25. . If a current carrying conductor is inclined to the magnetic field, then force ‘F’ is:
(A) Maximum
(B) Zero
(C) Near to zero
(D) BIl sinϕ
26. . The most important parts of d.c. machines are:
(A) Armature, Field coils & Commutator
(B) Frame and Pole Shoes
(C) Armature and Commutator
(D) Field coils and interpoles
27. . It provides mechanical support to d.c. machine:
(A) Yoke
(B) Interpoles
(C) Armature
(D) Commutator
28. . The purpose of yoke in a d.c. machine:
(A) Both (a) and (b)
(B) Providing low reluctance path to flux
(C) Reduce eddy current losses
(D) Mechanical protection
29. . The yoke of d.c. machine is made up of:
(A) Chrome steel
(B) Copper
(C) Aluminum
(D) Cast iron
30. . The number of field poles in a d.c. machines are:
(A) Always 2
(B) Odd
(C) Even
(D) Any of (b) or (c)
31. . The purpose of pole shoes in a d.c. machine is to:
(A) Spread out the flux in the air gap
(B) Reduce the reluctance of the magnetic path
(C) All of above
(D) Support the field coils
32. . The field poles of d.c. machine are made up of:
(A) Magnetic material
(B) Insulating material
(C) Conducting material
(D) Any of (a) or (c)
33. . The poles (& armature) of d.c. machine is laminated to reduce:
(A) Copper losses
(B) Eddy current losses
(C) Windage losses
(D) Friction losses
34. . The field coils (and armature winding) are made up of:
(A) Copper
(B) Cast iron
(C) Silver
(D) Silicon steel
35. . Interpoles are also called:
(A) Both (a) & (b)
(B) Compoles
(C) Small poles
(D) Commutating Poles
36. . Interpoles are connected to armature:
(A) In series
(B) Any of (a) or (b)
(C) None of these
(D) In parallel
37. . Interpoles are made up of:
(A) Wrought iron
(B) Any of these
(C) Silicon steel
(D) Cast steel
38. . The core of armature is made up of:
(A) Copper
(B) Silicon steel
(C) Aluminum
(D) Non Ferrous
39. . The armature core of d.c. machine is laminated to reduce:
(A) Weight
(B) Hysteresis losses
(C) Air pressure
(D) Eddy current losses
40. . The thickness of armature core lamination is about:
(A) 0.27 mm
(B) 0.35 mm
(C) 0.8 mm
(D) 0.5 mm
41. . It works as a rectifier in a d.c. machine:
(A) Armature
(B) Rocker
(C) Yoke
(D) Commutator
42. . Commutator segments are made up of:
(A) Copper
(B) Cast steel
(C) Silicon steel
(D) Any of these
43. . The purpose of commutator in a d.c. machine is to:
(A) Change the position of carbon brushes
(B) Convert a.c into pulsating d.c.
(C) Reduce effect of armature reaction
(D) Spread out the flux in air gap
44. . The part where the armature coils are connected is called:
(A) Yoke
(B) Commutator
(C) Rocker
(D) Interpoles
45. . The commutator segments should have this property:
(A) High reluctivity
(B) High permeability
(C) High conductivity
(D) High magnetic saturation
46. . This insulation is usually used between commutator segments:
(A) Paper
(B) Fabric
(C) Mica
(D) Tape of glass
47. . To collect current from commutator and make it available to the stationary external circuit is the function of:
(A) Yoke
(B) Rocker
(C) Brushes
(D) Commutator
48. . Brushes are made up of:
(A) Copper
(B) Cast iron
(C) Mica
(D) Carbon
49. . The thickness of insulation between commutator segments is:
(A) 0.8 mm
(B) 0.35 mm
(C) 0.5 mm
(D) 0.27 mm
50. . The shaft rotates smoothly with the use of this part:
(A) Commutator
(B) Rocker
(C) Brushes
(D) Bearings