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.Management Sciences
Category: Electrical Engineering Materials
Carbon bearings are used under which of the following conditions ?
A. Where lubrication is difficult or im-possible
B. Where corrosive chemical action exists
C. Where high temperature exists
D. All of the above
An H.R.C. fuse is_______________?
A. a ceramic body having metal and caps
B. a wire of platinum
C. a heavy cross-section of copper or aluminium
D. a ceramic tube having carbon rod inside it
The resistivity of a metal is a function of temperature because_____________?
A. the amplitude of vibration of the atoms varies with temperature
B. the electron density varies with temperature
C. the electron gas density varies with temperature
Addition of 0.3 to 4.5% silicon to iron ________ the electrical resistivity of iron?
A. increases
B. decreases
C. does not change
The conductivity of a metal is determined by____________?
A. the electronic concentration and the mobility of the free electrons
B. the number of valence electrons per atom
C. either (A) or (B)
D. none of the above
In thermocouples which of the following pairs is commonly used ?
A. Copper-constantan
B. Aluminium-tin
C. Silver-German silver
D. Iron-steel
Spark plug makes use of which of the following materials for insulation ?
A. Porcelain
B. Slate
C. Asbestos
D. Glass
The converse of hardness is known as______________?
A. malleability
B. toughness
C. softness
D. none of the above
The coils of D.C. motor starter are wound with wire of_______________?
A. copper
B. kanthal
C. manganin
D. nichrome
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