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

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219. 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

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220. Hard steel is suitable for making permanent magnets because
A. it has good residual magnetism
B. its hysteresis loop has large area
C. its mechanical strength is high
D. its mechanical strength is low

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221. 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

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222. Conductance is analogous to
A. permeance
B. reluctance
C. flux
D. inductance

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

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224. The unit of retentivity is
A. weber
B. weber/sq.m
C. ampere turn/metre
D. ampere turn

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