Electrical resistor bars are made of _______________?

Related Mcqs:

1. Which of the following has the lowest electrical resistivity ?

   A. Graphite
   B. Fireclay
   C. Alumina
   D. Zircon

2. Except _____________, all other refractories are bad conductors of electricity (i.e, have low electrical conductivity)?

   A. Fireclay
   B. Carborundum
   C. Graphite
   D. Chromite

3. The linear thermal expansion of _______________ bricks upto 1000 °C is very low of the order of ≤ 0.5 percent?

   A. Fireclay
   B. Silica
   C. Magnesite
   D. Corundum

4. Firing temperature is minimum (1250-1400 °C) for _______________ bricks?

   A. Fireclay
   B. Direct bonded basic
   C. Silica
   D. Magnesite

5. Refractories are dried in the _______________?

   A. Rotary kilns
   B. Tunnel kilns
   C. Sun
   D. None of these

6. Refractoriness/fusion points of ‘Superduty’ refractories is _______________ °C?

   A. 1520-1630
   B. 1630-1670
   C. > 1730
   D. > 2000

7. Presence of MgO in alumino-silicate refractories _______________ its refractoriness?

   A. Increases
   B. Lowers
   C. Does not affect
   D. Either A. or B.; depends on its quantity

8. High porosity refractory bricks have _______________?

   A. Poor resistance to the penetration of molten slag, metal & flue gases
   B. Poor heat conductivity & low strength
   C. Better thermal spalling resistance
   D. All A., B. and C.

9. Porosity of fireclay refractories is _______________ percent?

   A. 5-10
   B. 10-25
   C. 25-35
   D. 35-50

10. Pure oxide refractories are generally monocrystalline in nature and are self bonded _______________ bricks are generally used as moderator in nuclear reactors?

    A. Beryllia
    B. Carborundum
    C. Corundum
    D. Thoria