Materials and Components
In a metal, the valence electrons

Are shared only between neighbouring atoms
Either B or C
Are shared by all atoms
Are not shared

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Materials and Components
If a small amount of Cu is added to Ni conductor, then

Resistivity of Ni will decrease at all temperatures because Cu is a better conductor than Ni
Resistivity of Ni remains the same
Resistivity of Ni will increase at all temperatures as Cu destroys the periodicity of Ni and acts as defects
Residual resistivity of Ni at low temperature will increase as Cu atoms act as defect centres

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Materials and Components
In an intrinsic semiconductor, at a given temperature T

The number of electrons-hole pairs generated per second due to thermal motion are equal to the number of electron-hole pairs lost per second due to recombination
The number of electron-hole pairs generated per second due to thermal motion is always less than the number of electron-hole pairs lost per second due to recombination
Any of the above
The number of electron hole pairs generated per second due to thermal motion is always more than the number of electron-hole pairs lost per second due to recombination

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Materials and Components
Electrical contact materials used in switches, brushes, relay must possess

Low thermal conductivity and low melting pointL
High thermal conductivity and low melting point
Low thermal conductivity and high melting point
High thermal conductivity and high melting point

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