50+ Simple Magnetic Circuits Questions

                     

1. What is a permeable substance?
a) Any good conductor
b) Any bad conductor
c) Any strong magnet
d) Any substance through which the magnetic lines of force can pass easily
Answer: d


2. Materials having good retentivity are?
a) Strong magnets
b) Weak magnets
c) Temporary magnets
d) Permanent magnets
Answer: d


3. Magnetic field exists along which of the following?
a) Moving charges
b) Stationary charges
c) Copper
d) Iron
Answer: a


4. Magnetomotive force is equal to__________________
a) current * number of turns
b) current / number of turns
c) current / number of turns per unit length
d) current * number of turns per unit length
Answer: a


5. Unit of MMF is ______________
a) A/m
b) A-m
c) A
d) unitless
Answer: c

6. When a bar magnet is broken into two pieces, which of the following are true?
a) The magnet loses its magnetism
b) The magnet has only north pole left
c) The magnet has only south pole left
d) The magnet turns into two new bar magnets
Answer: d


THESE ARE Simple Magnetic Circuits Questions

7. When an electric current flows into the page, what is the direction of the magnetic field?
a) Clockwise
b) Anti-clockwise
c) Cannot be determined
d) Parallel to the current
Answer: a

8. When an electric current flows out of the page, what is the direction of the magnetic field?
a) Clockwise
b) Anti-clockwise
c) Cannot be determined
d) Parallel to the current
Answer: b

9. The relation between the direction of current and the direction of magnetic field is?
a) Same direction
b) Opposite direction
c) Perpendicular
d) Unrelated
Answer: c

10. Permeability of free space is also known as _________
a) Magnetic constant
b) Electric constant
c) Electrostatic constant
d) Magnetostatic constant
Answer: a

11. A substance whose permeability is less than the permeability of free space is?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Not a magnetic substance
Answer: a

12. Which, among the following, have negative susceptibility?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Not a magnetic substance
Answer: a

13. Which, among the following, have positive susceptibility?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Both paramagnetic and ferromagnetic
Answer: d

14. A substance whose permeability is more than the permeability of free space is?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Both paramagnetic and ferromagnetic
Answer: d

15. The unit for permeability of free space is?
a) Henry
b) Henry-m
c) Henry/m
d) Henry/m2
Answer: c

16. Which among the following, is a correct expression for µ0.
a) µ0=BH
b) µ0=B/H
c) µ0=H/B
d) µ0=BH2
Answer: b

17. Calculate the magnetic flux density if the magnetic field strength is 2A/m.
a) 4*pi*10-7T
b) 8*pi*10-7T
c) 10*pi*10-7T
d) 12*pi*10-7T
Answer: b

18. Calculate the magnetic field strength if the magnetic flux density is 4*piT.
a) 10-7/16*pi2A/m
b) 10-7A/m
c) 107A/m
d) 10-7A
Answer: c

19. Calculate the magnetic flux density if the magnetic field strength is 3A/m.
a) 4*pi*10-7T
b) 8*pi*10-7T
c) 10*pi*10-7T
d) 12*pi*10-7T
Answer: d

20. What is the unit for relative permeability?
a) H-m
b) H/m
c) H2/m
d) No unit
Answer: d

THESE ARE Simple Magnetic Circuits Questions

21. Which of the following expressions is correct with respect to relative permeability?
a) B = µrµ0/H
b) B = µrµ0H
c) B = µr0H
d) B = µrµ0/H2
Answer: b

22. A substance whose relative permeability is less than the permeability of free space is?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Not a magnetic substance
Answer: a

23. A substance whose relative permeability is more than the permeability of free space is?
a) Diamagnetic
b) Paramagnetic
c) Ferromagnetic
d) Both paramagnetic and ferromagnetic
Answer: d

24. Diamagnetic substances have relative permeability_____________
a) Greater than 1
b) Less than 1
c) Equal to 1
d) Zero
Answer: b

25. Paramagnetic substances have relative permeability_____________
a) Greater than 1
b) Less than 1
c) Equal to 1
d) Zero
Answer: a

26. As the temperature increases up to the Curie temperature, the relative susceptibility of ferromagnetic materials?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: a


THESE ARE Simple Magnetic Circuits Questions

27. As the temperature increases beyond the Curie temperature, the relative susceptibility of ferromagnetic materials?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: b

28. Reciprocal of reluctance is __________
a) Permeance
b) Susceptibility
c) Resistance
d) Conductance
Answer: a

29. Reluctance is ________________ to the length of the material.
a) Directly proportional
b) Inversely proportional
c) Not related
d) Reluctance is ________________ to the length of the material.
Answer: a

30. Reluctance is ________________ to the area of cross section the material.
a) Directly proportional
b) Inversely proportional
c) Not related
d) Equal
Answer: b

31. When the length of the material increases, what happens to reluctance?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

32. When the area of cross section of the material increases, what happens to reluctance?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

33. Unit of reluctance is?
a) AWb
b) A2/Wb
c) Wb/A
d) A/Wb
Answer: d

34. The electrical equivalent of reluctance is?
a) Resistance
b) Inductance
c) Capacitance
d) Conductance
Answer: a

35. As the magnetic field strength increases, reluctance?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a

36. As the magnetic flux density increases, the reluctance _____________
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: b

THESE ARE Simple Magnetic Circuits Questions

37. Calculate the reluctance when the magnetomotive force is 10A turns and the flux is 5Wb.
a) 0.5A/Wb
b) 5A/Wb
c) 10A/Wb
d) 2A/Wb
Answer: d

38. Ohm’s law for magnetic circuits is _________
a) F=ϕS
b) F=ϕ/S
c) F=ϕ2S
d) F=ϕ/S2
Answer: a

39. What happens to the MMF when the magnetic flux decreases?
a) Increases
b) Decreases
c) Remains constant
d) Becomes zero
Answer: b

40. Calculate the MMF when the magnetic flux is 5Wb and the reluctance is 3A/Wb.
a) 10At
b) 10N
c) 15N
d) 15At
Answer: d

41. A ring having a cross-sectional area of 500 mm2, a circumference of 400 mm and ϕ=800microWb has a coil of 200 turns wound around it. Calculate the flux density of the ring.
a) 1.6T
b) 2.6T
c) 3.6T
d) 4.6T
Answer: a

42. A ring having a cross-sectional area of 500 mm2, a circumference of 400 mm and ϕ=800microWb has a coil of 200 turns wound around it. Relative permeability of ring is 380. Calculate the reluctance.
a) 1.68 * 10-4A/Wb
b) 1.68 * 104 A/Wb
c) 1.68 * 106 A/Wb
d) 1.68 * 10-6A/Wb
Answer: c

43. A ring having a cross-sectional area of 500 mm2, a circumference of 400 mm and ϕ=800microWb has a coil of 200 turns wound around it. Relative permeability of ring is 380. Calculate the magnetomotive force.
a) 1442At
b) 1342At
c) 1432At
d) 1344At
Answer: d

44. A ring having a cross-sectional area of 500 mm2, a circumference of 400 mm and ϕ=800microWb has a coil of 200 turns wound around it. Relative permeability of ring is 380. Calculate the magnetising current.
a) 6.7A
b) 7.7A
c) 7.6
d) 6.1A
Answer: a

45. Can we apply Kirchhoff’s law to magnetic circuits?
a) Yes
b) No
c) Depends on the circuit
d) Insufficient information provided
Answer: a

46. What is MMF?
a) Magnetic Machine Force
b) Magnetomotive Force
c) Magnetic Motion Force
d) Magnetomotion Force
Answer: b

47. The equivalent of the current I in magnetic ohm’s law is?
a) Flux
b) Reluctance
c) MMF
d) Resistance
Answer: a


THESE ARE Simple Magnetic Circuits Questions

48. The B/H characteristics can be determined using _______
a) Ammeter
b) Fluxmeter
c) Voltmeter
d) Multimeter
Answer: b

49. The B/H curve can be used to determine?
a) Iron loss
b) Hysteresis loss
c) Voltage loss
d) Eddy current loss
Answer: b

50. The B/H ratio is not constant for ________
a) Diamagnetic materials
b) Ferromagnetic materials
c) Paramagnetic materials
d) Non-magnetic materials
Answer: b

51. When using a fluxmeter, if the flux changes from Φ to -Φ, what happens to the current?
a) Becomes zero
b) Becomes infinity
c) Remains the same
d) Reverses
Answer: d

52. Why is the coil of a ballistic galvanometer wound on a non- metallic former?
a) To minimise damping when high resistance is connected in series
b) To maximise damping when high resistance is connected in series
c) To minimise damping when high resistance is connected in parallel
d) To maximise damping when high resistance is connected in parallel
Answer: a

53. The ballistic galvanometer is usually lightly damped so that ________
a) It can oscillate
b) It will remain stable
c) Amplitude of the first swing is very large
d) Amplitude of the first swing is very small
Answer: c

54. PMMC instruments can be used as a fluxmeters by _______
a) Using a low resistance shunt
b) Removing the control spring
c) Making the control springs having a large moment of inertia
d) Using a high resistance in series
Answer: b

55. Hysteresis loss is determined from _______
a) B/H curve
b) H/B curve
c) BH curve
d) B2H curve
Answer: c

56. What is a PMMC instrument?
a) Permanent moving magnet coil instrument
b) Permanent machine magnet coil instrument
c) Permanent moving machine coil instrument
d) Premature moving magnet coil instrument
Answer: a

57. B/H curve shows the relationship between?
a) Magnetic field strength and magnetic flux
b) Magnetic field strength and magnetic flux density
c) Current and magnetic flux density
d) Voltage and magnetic flux density
Answer: b

THESE ARE Simple Magnetic Circuits Questions


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