Magnetic Circuits MCQ


41. Which point on the B-H curve in the above Fig. represents the average permeability ?

(i) point 5
(ii) point 2
(iii) point 1
(iv) point 4

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42. The hysteresis loop of a material having low retentivity is

(i) wide
(ii) narrow
(iii) very wide
(iv) none of above

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43. The SI unit of µo is

(i) AT/m
(ii) Wb/m
(iii)Wb/AT-m
(iv) none of above

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44. The point 2 in the above Fig. represents

(i) residual flux density
(ii) coercive force
(iii) saturation flux density
(iv) none of above

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45. Which point in the above Fig. corresponds to coercive force ?

(i) point 1
(ii) point 5
(iii) point 2
(iv) point 6

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46. The hysteresis loop shown in the above Fig. is for

(i) air
(ii) soft iron
(iii) steel
(iv) copper

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47. How would the loop in the above Fig. appear for a material with much less retentivity ?

(i) narrower
(ii) wider
(iii) no change
(iv) very wide

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48. The unit of relative permeability is

(i) AT/m
(ii) N/Wb
(iii) AT/m2
(iv) a number

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49. The hysteresis loss in a ferromagnetic material is

(i) directly proportional to area of loop
(ii) inversely proportional to area of loop
(iii) directly proportional to square of area of loop
(iv) none of above

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50. At low frequencies, the material used for transformer cores is

(i) copper
(ii) silicon iron
(iii) soft iron
(iv) none of above

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51. At high frequencies, the material used for transformer cores is

(i) silicon iron
(ii) soft iron
(iii) ferrite
(iv) none of above

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52. In practical  magnetic circuits, the air-gap is kept

(i) very small
(ii) large
(iii) very large
(iv) none of above

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53. The minimum relative permeability of a material can be

(i) 1
(ii) slightly less than 1
(iii) 0.005
(iv) none of above

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54. In non-magnetic materials descending and ascending B-H curves

(i) coincide
(ii) do not coincide
(iii) sometime coincide and sometime not
(iv) none of above

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55. What is the magnetic field intensity in a material whose relative permeability is 1 when the flux density is 0.005 T ?

(i) 250 AT/m
(ii) 452 AT/m
(iii) 3980 AT/m
(iv) 1715 AT/m

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56. The relative permeability of air is

(i) 0
(ii) 1
(iii) infinite
(iv) none of above

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57. The slope of B-H curve of a material gives its

(i) absolute permeability
(ii) relative permeability
(iii) retentivity
(iv) none of above

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58. The value of relative permeability of ferro-magnetic materials with increase in temperature

(i) increases
(ii) decreases
(iii) remains the same
(iv) none of above

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59. A permanent magnet should have

(i) low remanence
(ii) high remanence
(iii) zero remanence
(iv) none of above

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60. An electromagnet uses

(i) soft iron core
(ii) steel core
(iii) nickel core
 (iv) copper core

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