# 50+ Simple Magnetic Circuits Questions

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

THESE ARE Simple Magnetic Circuits Questions

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

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

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

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

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

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

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

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

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

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