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.Management Sciences
Category: Magnetic Circuit
Energy stored by a coil is doubled when its current is increased by percent___________?
0
A. 25
B. 50
C. 41.4
D. 100
An air gap is usually inserted in magnetic circuits to____________?
A. increase m.m.f.
B. increase the flux
C. prevent saturation
D. none of the above
The relative permeability of a ferromagnetic material is_____________?
A. less than one
B. more than one
C. more than 10
D. more than 100 or 1000
Hysteresis loss least depends on____________?
A. volume of material
B. frequency
C. steinmetz coefficient of material
D. ambient temperature
A ferrite core has less eddy current loss than an iron core because_______________?
A. ferrites have high resistance
B. ferrites are magnetic
C. ferrites have low permeability
D. ferrites have high hysteresis
Those materials are well suited for making permanent magnets which have ________ retentivity and _________ coercivity
A. low, high
B. high, high
C. high, low
D. low, low
Silicon steel is used in electrical machines because it has_____________?
A. low coercivity
B. low retentivity
C. low hysteresis loss
D. high coercivity
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
Permanent magnets are normally made of_____________?
A. alnico alloys
B. aluminium
C. cast iron
D. wrought iron
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