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 ?

Related Mcqs:

1. 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.

2. Velocity of a gas in sound is not proportional to (where, T = Absolute temperature of the gas. P = Absolute pressure of the gas. y = Ratio of specific heats (Cp/Cv) ρ = specific weight of the gas) ?

   A. √T
   B. 1/√P
   C. √y
   D. 1/√ρ

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

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

4. Probability of cavitation occuring becomes very high, when the local _______________ resulting ?

   in water bubbles formation, which on rupture cause cavitation
   A. Pressure falls below the vapour pressure
   B. Pressure becomes very high
   C. Temperature becomes low
   D. All A, B & C

5. Square steel key is normally strong in failure by shear & crushing. Keys are normally made of _______________ steel bars?

   A. Hot rolled mild
   B. Cold rolled mild
   C. Forged
   D. Machinable stainless

6. All the atoms of the world comprise of electrons, proton & neutron except that of ______________ atom in which neutron is absent ?

   A. Deuterium
   B. Hydrogen
   C. Neon
   D. Helium

7. Electrolytic reduction cell used for conversion of calcined Al2O3 to Al is a carbon lined furnace operating at 800-900 °C. The purpose of electric current supplied to the furnace is to___________________?

   A. Achieve very high purity of aluminium (99.9%)
   B. Keep the electrolyte in liquid condition by the generation of heat
   C. Electrolytically dissociate alumina
   D. Both B. & C.

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

   A. 10-3
   B. 103
   C. 10-15
   D. 1015

9. Elimination of brittleness resulting from welding of saw blades is done by __________________ of the welded portion ?

   A. Annealing
   B. Toughening
   C. Work hardening
   D. Tempering

10. The heat of neutralisation remains constant, when there is a reaction between dilute solutions of strong _____________________?

    A. Base and strong acid
    B. Base and weak acid
    C. Acid and weak base
    D. None of these