Magnetic Circuit

1. A ferrite core has less eddy current loss than an iron core because

  1. ferrites have high resistance
  2. ferrites are magnetic
  3. ferrites have low permeability
  4. ferrites have high hysteresis

Correct answer: (A)
ferrites have high resistance

2. A material for good magnetic memory should have

  1. low hysteresis loss
  2. high permeability
  3. low retentivity
  4. high retentivity

Correct answer: (D)
high retentivity

3. An air gap is usually inserted in magnetic circuits to

  1. increase m.m.f.
  2. increase the flux
  3. prevent saturation
  4. none of the above

Correct answer: (C)
prevent saturation

4. Conductance is analogous to

  1. permeance
  2. reluctance
  3. flux
  4. inductance

Correct answer: (A)

5. Conductivity is analogous to

  1. retentivity
  2. resistivity
  3. permeability
  4. inductance

Correct answer: (C)

6. Energy stored by a coil is doubled when its current is increased by percent.

  1. 25
  2. 50
  3. 41.4
  4. 100

Correct answer: (C)

7. Hard steel is suitable for making permanent magnets because

  1. it has good residual magnetism
  2. its hysteresis loop has large area
  3. its mechanical strength is high
  4. its mechanical strength is low

Correct answer: (A)
it has good residual magnetism

8. Hysteresis loss least depends on

  1. volume of material
  2. frequency
  3. steinmetz coefficient of material
  4. ambient temperature

Correct answer: (D)
ambient temperature

9. If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be

  1. zero
  2. small
  3. large
  4. none of the above

Correct answer: (C)

10. In a magnetic material hysteresis loss takes place primarily due to

  1. rapid reversals of its magnetisation
  2. flux density lagging behind magnetising force
  3. molecular friction
  4. it high retentivity

Correct answer: (D)
it high retentivity

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