_______________is universally used for windings of electrical machines because it is easily workable without any possibility of fracture?
(A) Silver
(B) Steel
(C) Aluminium
(D) Copper
__________ has a low relative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable?
(A) Cast steel
(B) Aluminium
(C) Soft steel
(D) Cast iron
Commercial available medium size machines have a speed range of __________ ?
(A) 200 to 400 r.p.m
(B) 600 to 1000 r.p.m
(C) 1000 to 1500 r.p.m
(D) 2000 to 2500 r.p.m
The change in flux linkages can be caused in which of the following ways ?
(A) The flux is constant with respect to time and is stationary and the coil moves through it
(B) The coil is stationary with respect to flux and the flux varies in magnitude with respect to time
(C) Both the changes mentioned above occur together, i.e., the coil moves through a time varying field
(D) All of the above
The action of electromagnetic machines can be related to which of the following basic principles __________?
(A) Induction
(B) Interaction
(C) Alignment
(D) All of the above
The design of mechanical parts is particularly important in case of __________ speed machines?
(A) low
(B) medium
(C) high
(D) any of the above
impose limitation on design____________?
(A) Saturation
(B) Temperature rise
(C) Efficiency
(D) Power factor
(D) All above
If an insulating material is operated beyond the maximum allowable temperature, its life is_____________?
(A) drastically increased
(B) drastically reduced
(C) unaffected
(D) none of the above
Electrical machines having a power output up to about 750 W may be called__________machines?
(A) small size
(B) medium size
(C) large size
(D) any of the above
Hydrogen has a heat transfer co-efficient __________ times that of air?
(A) 1.5
(B) 2.5
(C) 3.5
(D) 4.5