Magnetic Circuit Objective Electrical Questions - Set 01 - ObjectiveBooks

Practice Test: Question Set - 01

1. Those magnetic materials are best suited for making armature and transformer cores which have ________permeability and _________hysteresis loss.
(A) High, high
(B) Low, high
(C) High, low
(D) Low, low

2. In a magnetic material hysteresis loss takes place primarily due to
(A) Rapid reversals of its magnetization
(B) Flux density lagging behind magnetizing force
(C) Molecular friction
(D) It high retentivity

3. Silicon steel is used in electrical machines because it has
(A) Low coercivity
(B) Low retentivity
(C) Low hysteresis loss
(D) High coercivity

4. Reciprocal of reluctance is
(A) Reluctivity
(B) Permeance
(C) Permeability
(D) Susceptibility

5. Hysteresis loss least depends on
(A) Volume of material
(B) Frequency
(C) Steinmetz’s coefficient of material
(D) Ambient temperature

6. An air gap is usually inserted in magnetic circuits to
(A) Increase m.m.f.
(B) Increase the flux
(C) Prevent saturation
(D) None of the above

7. The rate of rise of current through an inductive coil is maximum
(A) At 63.2% of its maximum steady value
(B) At the start of the current flow
(C) After one time constant
(D) Near the final maximum value of current

8. Conductivity is analogous to
(A) Retentivity
(B) Resistivity
(C) Permeability
(D) Inductance

9. The property of a material which opposes the creation of magnetic flux in it is known as
(A) Reluctivity
(B) Magneto-motive force
(C) Permeance
(D) Reluctance

10. A ferrite core has less eddy current loss than an iron core because
(A) Ferrites have high resistance
(B) Ferrites are magnetic
(C) Ferrites have low permeability
(D) Ferrites have high hysteresis

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