Magnetic Circuit(Electrical Engineering Questions ) Questions and Answers

Question 1. Those magnetic materials are best suited for making armature and transformer cores which have ________ permeability and ________ hystersis loss
  1.    high, high
  2.    low, high
  3.    high, low
  4.    low, low
Explanation:-
Answer: Option C. -> high, low
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 2. A material for good magnetic memory should have____________?
  1.    low hysteresis loss
  2.    high permeability
  3.    low retentivity
  4.    high retentivity
Explanation:-
Answer: Option D. -> high retentivity
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 3. The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is__________Vs
  1.    50
  2.    20
  3.    0.05
  4.    500
Explanation:-
Answer: Option B. -> 20
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 4. 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
Explanation:-
Answer: Option C. -> large
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 5. Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it___________?
  1.    lowers their power efficiency
  2.    increases their cost of manufacture
  3.    leads to their increased weight
  4.    produces fringing
Explanation:-
Answer: Option A. -> lowers their power efficiency
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 6. The rate of rise of current through an inductive coil is maximum_____________?
  1.    at 63.2% of its maximum steady value
  2.    at the start of the current flow
  3.    after one time constant
  4.    near the final maximum value of current
Explanation:-
Answer: Option B. -> at the start of the current flow
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 7. 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
Explanation:-
Answer: Option C. -> prevent saturation
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 8. The unit of magnetic flux is______________?
  1.    henry
  2.    weber
  3.    ampereturn/weber
  4.    ampere/metre
Explanation:-
Answer: Option B. -> weber
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 9. Permanent magnets are normally made of_____________?
  1.    alnico alloys
  2.    aluminium
  3.    cast iron
  4.    wrought iron
Explanation:-
Answer: Option A. -> alnico alloys
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
Question 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
Explanation:-
Answer: Option D. -> it high retentivity
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!
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