MCQ Hysteris and Eddy current Losses|Magnetic circuits MCQ

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MCQ Hysteris and Eddy current Losses: Magnetic circuits MCQ

MCQ Hysteris and Eddy current Losses

  1. Silicon steel is used for transformer core because
    (a) it reduces hysteresis loss
    (b) it reduces eddy-current loss
    (c) it increases core permeability
    (d) it reduces magnetostriction noise

2. Transformer care is built from this stampings because
(a) it reduces eddy-current loss
(b) it reduces hysteresis loss
(c) it reduces both hysteresis and eddy-current loss
(d) it increases the mechanical strength of the core

3. Maximum flux established in an ac-excited iron core is determined by
(a) impressed frequency coil
(b) impressed voltage only
(c) both impressed voltage and frequency
(d) reluctance of the core

4. The unit of flux density is
(a) Tesla (b) ATH/m2
(c) Wb/m2 (d) All three are equivalent

5. The unit of inductance is
(a) Wb T/A (b) Vs/A
(c) H-turns2 (d) All three are equivalent

6. Eddy current guess are proportional to (of = frequency, B = flux density, t = laminative thickness)
(a) f, B, t (b) f, B, t2 (c) f, B2, t2 (d) f2, B2, t2

7. Magnetostriction noise in ferromagnetic materials is caused by
(a) hysteresis loss
(b) eddy-current loss
(c) changes in linear dimensions of crystals under dc excitation
(d) changes in linear dimension of crystals under ac excitation

8. A coil of 1000 runs is wound on a core and a current of 1A flowing through the coil creates a core flux
of 1 mWb. The energy stored in the magnetic field is
(a) 1/a J (b) 1/2 J (c) 1 J (d) 1 2 J

9. In magnetic circuit, a current of 1 A flowing in the exciting winding produces flux of 1 Wb. If the circuit
reluctance is doubled, the exciting current should be
(a) 2 A (b) 0.5 A (c) 1 A (d) 1.5 A

10.A coil wound on a magnetic core is excited from an ac voltage source. The source voltage and its
frequency are both doubled and the eddy-current loss in the core will become
(a) half (b) remains same (c) double (d) four times

Multiple-Choice Questions

  1. (b) 2. (a) 3. (c) 4. (d) 5. (d) 6.(d) 7. (a) 8. (b) 9. (a) 10. (d)

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