3428. Which is not an acidic refractory ?
Silica
Fireclay
High alumina refractory
Carbon black
✅ The correct answer is option D.
3434. __________ is not a single oxiderefractory.
Zirconia
Silicon carbide
Magnesia
None of these
✅ The correct answer is option B.
3439. Magnesite refractories are used for the construction of those furnaces, which are
not required to resist the corrosive action of basic slag.
not subjected to fluctuation in temperature.
used for raising & maintaining high temperature.
both (b) and (c)
✅ The correct answer is option D.
3441. A fast breeder reactor
utilises fast neutrons for causing fission.
converts fertile material (e.g., U-238) into fissile material (Pu-239).
normally employs molten sodium as coolant.
all (a), (b) and (c).
✅ The correct answer is option D.
3445. The ratio of mass of a neutron to that of an electron is about 1839. What is the ratio of the mass of a proton to that of an electron?
159
1837
2537
10000
✅ The correct answer is option B.
3412. Radioactive decay is a __________ change.
chemical
nuclear
physical
none of these
✅ The correct answer is option B.
3417. The size of an atom is of the order of one
°Angstrom
fermi
micron
mm
✅ The correct answer is option A.
3427. Fission of U-235 on slow neutron bombardment can be represented by
92U235 + 3 γ1 56Ba143 + 36Kr90
92U235 + 0n1 56Ba143 + 36Kr90 + 3 0n1
92U235 + 0n1 56Ba143 + 36Kr90 + 3 0n1 + Q (energy)
92U235 + 0n1 92U236 + 30n1+ Q (energy)
✅ The correct answer is option C.
3432. Moderating material used in a thermal-reactor should be a
good absorber of neutrons.
solid substance.
poor absorber of neutrons.
none of these.
✅ The correct answer is option C.
3437. The main ore of thorium is
pitchblende
monazite sand
limonite
galena
✅ The correct answer is option B.