A. alnico alloys
B. aluminium
C. cast iron
D. wrought iron
Related Mcqs:
- 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 - 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 - When both the inductance and resistance of a coil are doubled the value of________________?
A. time constant remains unchanged
B. initial rate of rise of current is doubled
C. final steady current is doubled
D. time constant is halved - Conductivity is analogous to____________?
A. retentivity
B. resistivity
C. permeability
D. inductance - Laminated cores, in electrical machines, are used to reduce____________?
A. copper loss
B. eddy current loss
C. hysteresis loss
D. all of the above - The unit of reluctance is_____________?
A. metre/henry
B. henry/metre
C. henry
D. 1/henry - In a magnetic material hysteresis loss takes place primarily due to___________?
A. rapid reversals of its magnetisation
B. flux density lagging behind magnetising force
C. molecular friction
D. it high retentivity - 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 rate of rise of current through an inductive coil is maximum_____________?
A. at 63.2% of its maximum steady value
B. at the start of the current flow
C. after one time constant
D. near the final maximum value of current - The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is__________Vs
A. 50
B. 20
C. 0.05
D. 500
