Wednesday, September 2, 2020

Chapter 3 : Electromagnetism- Page 16

Chapter 3 : Electromagnetism

151. In a magnetic material hysteresis loss takes place primarily due to
A. molecular friction
B. it high retentivity
C. rapid reversals of its magnetization
D. flux density lagging behind magnetising force

... Answer is ( B)



152. If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be

A. zero
B. small
C. large
D. none of the above

... Answer is (C)


153. Hard steel is suitable for making permanent magnets because

A. its mechanical strength is high
B. its mechanical strength is low

it has good residual magnetism
D. its hysteresis loop has large area

... Answer is (C)



154. Silicon steel is used in electrical machines because it has

A. low co-ercivity
B. low retentivity
C. low hysteresis loss
D. high co-ercivity

  ... Answer is (C)


155. Conductance is analogous to
Answer is (C)


156. The property of a material which opposes the creation of magnetic flux in it is known as
B. magnetomotive force
C. permeance
D. resistance

  ... Answer is (A)



157. The unit of retentivity is

A. weber
B. weber/sq.m
C. ampere turn/metre
D. ampere turn

... Answer is (B)


158. Reciprocal of reluctance is

A. permeability
B. susceptibility

D. perrneance

... Answer is (D)


159. While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electrical circuit?

A. E.m.f
B. Current
C. Current density
D. Conductivity
  ... Answer is (B)


160.  The unit of reluctance is

B. 1/henry

D. henry/metre

  ... Answer is (B)



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