Electrical conductivities of semi-conductors are of the order of ______________ ohm/cm ?

Related Mcqs:

1. A steam pipe is intended to be insulated with two layers of insulating materials of different thermal conductivities. For minimum heat transfer to take place_________________?

   A. The better insulation material should be put just next to pipe (i.e., inside)
   B. The better insulating material should be put outside
   C. Either of the insulating material could be put on either side
   D. Steam temperature is considered before deciding as to which insulating material is to be put
   inside (i.e., just next to the pipe)

2. Materials having resistivity ranging from 1 to 100 ohm. cm is termed as___________________?

   A. Conductor
   B. Insulator
   C. Semi-conductor
   D. None of these

3. _______________ test can be termed as the semi-destructive test?

   A. Impact
   B. Torsion
   C. Hardness
   D. Charpy

4. A semi-conductor is damaged & behaves like a conductor, on passing a strong electric current through it, because it heats up the crystals & breaks the covalent bonds resulting in _______________ electrons ?

   A. Lack of free
   B. Excess of
   C. Decrease in
   D. None of these

5. Direct conversion of thermal energy to electrical energy is facilitated by the____________________?

   A. Fuel cells
   B. Photo voltaic cell
   C. Magneto hydrodynamic generator
   D. None of these

6. Resistance of an electrical conductor is proportional to its (where, l = length and A = crosssectional area of the conductor)________________?

   A. A
   B. l
   C. A2
   D. Both A. & B.

7. With increase in temperature, the electrical conductivity of a _________________ decreases ?

   A. Semi-conductor
   B. Metal or alloy
   C. Dielectric
   D. None of these

8. Which of the following materials has the poorest electrical conductivity ?

   A. Carbon
   B. Aluminium
   C. Silver
   D. Stainless steel

9. In electrical resistance welding, distortion results from the use of improper________________?

   A. Clamping methods
   B. Electrodes
   C. Current
   D. Filler material

10. The ratio of thermal & electrical conductivity is same for all the metals at the same temperature; and at around room temperature, this ratio is proportional to(where, T = absolute temperature, °K) ?

    A. T
    B. 1/T
    C. T2
    D. 1/T2