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

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2. A material for good magnetic memory should have

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

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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

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4. Conductance is analogous to

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

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5. Conductivity is analogous to

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

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

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

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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

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8. Hysteresis loss least depends on

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

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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

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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

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