A carbon resistor contains
pulverized coal
solid carbon granules
carbon crystals
finely divided carbon black.
finely divided carbon black.
The impurity atoms is semiconductors
inject more charge carriers
increase the kinetic energy of valence electrons
reduce the energy gap
all of the above
reduce the energy gap
Low resistivity materials are used in
all above applications
house wiring
transmission and distribution lines
transformer motor and generator windings
all above applications
The forbidden gap in an insulator is
large
nil
small
any of the above
large
Which of the following factors affect resistivity of metals ?
Temperature
All of the above
Age hardening
Alloying
All of the above
The conductivity of an extrinsic semiconductor with temperature
remains constant
decreases
increases
None of the above
remains constant
The current due to electron flow in conduction band is the hole current in valence band.
any of the above
less than
equal to
greater than
greater than
For a hole which of the following statements is incorrect ?
Holes can exist in certain semiconductors only
Holes may constitute an electric current
Holes can exist in any material including conductors
Holes can be considered as a net positive charge
Holes can exist in any material including conductors
Surface resistance of an insulating material is reduced due to the
both and
neither nor
humidity in the atmosphere
smoky and dirty atmosphere
both and
In conductors conduction of electricity takes place due to movement of
electrons only
negative ions only
positive ions only
positive and negative ions
electrons only
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