Simple Magnetic Circuit MCQ - Objective Question Answer for Magnetic Circuit Quiz

41. 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

We know that:

F = ϕS

Substituting the given values from the question, we get

MMF = 15At.

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. Calculate the flux density of the ring.

A. 1.6T
B. 2.6T
C. 3.6T
D. 4.6T

Answer: A

Flux is given as

ϕ = BA = > Flux density B = ϕ/A

Substituting the values, we get B = 1.6T.

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. The relative permeability of the 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

Reluctance = l/(µ×A) = l/(µ_rµ₀×A)

Substituting the values, we get Reluctance = 1.68×10⁶ A/Wb.

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. The relative permeability of the ring is 380. Calculate the magnetomotive force.

A. 1442 At
B. 1342 At
C. 1432 At
D. 1344 At

Answer: D

Reluctance = l/(µ×A) = l/(µ_rµ₀×A)

Substituting the values, we get Reluctance S = 1.68×106 A/Wb.

F = ϕS

Substituting the given values, we get F = 1344 At.

45. 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. The relative permeability of the ring is 380. Calculate the magnetizing current.

A. 6.7 A
B. 7.7 A
C. 7.6 A
D. 6.1 A

Answer: A

Reluctance = l/(µ×A) = l/(µ_rµ₀×A)

Substituting the values, we get Reluctance

S = 1.68×106 A/Wb.

F = ϕS Substituting the given values, we get

F = 1344At.

I = F/N

Substituting the values from the question, we get I = 6.7A.

46. Can we apply Kirchhoff’s law to magnetic circuits?

A. Yes
B. No
C. Depends on the circuit
D. Insufficient information provided

Answer: A

Magnetic circuits have an equivalent to the potential difference of electric circuits. This magnetic potential difference allows us to apply Kirchhoff’s laws to magnetic circuit analysis.

47. What is MMF?

A. Magnetic Machine Force
B. Magnetomotive Force
C. Magnetic Motion Force
D. Magnetomotion Force

Answer: B

MMF stands for magnetomotive force. Actually, it is not a force. It is analogous to potential in an electric field.

48. The equivalent of the current I in magnetic ohm’s law is?

A. Flux
B. Reluctance
C. MMF
D. Resistance

Answer: A

The equivalent of the current I in magnetic ohm’s law is flux.

The equivalent of current in magnetic ohm’s law is flux as:

V = IR is equivalent to F = ϕS.

49. The B/H characteristics can be determined using _______

A. Ammeter
B. Fluxmeter
C. Voltmeter
D. Multimeter

Answer: B

The fluxmeter is an electronic display instrument used to measure the magnetic flux of permanent magnets hence it can be used to determine B/H characteristics.

50. The B/H curve can be used to determine?

A. Iron loss
B. Hysteresis loss
C. Voltage loss
D. Eddy’s current loss

Answer: B

Hysteresis loss is a heat loss due to the reversal of magnetization of the transformer core whenever it is subjected to a changing magnetic field. It can be determined using the B/H curve.

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