A. 30
B. 50
C. 70
D. 90
Related Mcqs:
- With increase in the alumina content, the refractoriness of high alumina refractories_________________?
A. Increases
B. Decreases
C. Remain same
D. May increase or decrease - An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture ?
A. Cork
B. Saw dust
C. Sand
D. Chemically prepared foam - Water content in ground refractory material to be shaped into bricks by hand moulding is about _____________ percent?
A. 5
B. 20
C. 40
D. 55 - Thermal diffusivity of a refractory brick is high, when its ______________ is high?
A. Density
B. Specific heat
C. Thermal conductivity
D. None of these - Beryllia (which is used in making crucibles for melting uranium & thorium) is superior to alumina in all respects for high temperature (> 1900°C ) use, except______________?
A. Cost
B. Electrical conductivity
C. Thermal conductivity
D. Fusion point - N2 content in a urea sample was found to be only 42%. What is the actual urea content of the sample? (Molecular weight of urea = 60) ?
A. 80%
B. 90%
C. 95%
D. 98% - 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. - The maximum adiabatic flame temperature of fuels in air is ____________ the maximum flame temperature in pure oxygen?
A. Lower than
B. Higher than
C. Same as
D. Not related to - Thermal conductivity of refractory bricks____________________?
A. Increases with decrease in porosity
B. Decreases with decreases in porosity
C. Is independent of its porosity and is maximum for insulating bricks
D. Increases with the amount of air entrapped in pores - Test piece for determination of RUL of a refractory is heated in a/an__________________?
A. Oxidising atmosphere
B. Reducing atmosphere
C. Electric furnace
D. Neutral atmosphere
