76.  Pick out the wrong statement.

a

  Positron is heavier than a proton.

b

 A, b-ray particle is identical with an electron.

c

 The nucleus of a hydrogen atom is identical with a proton.

d

 Mass of an electron is about 1/1800th of the lightest nucleus.

Answer & Explanation
Answer : Option A

77.  The Chernobyl nuclear disaster occurred in a power plant at Ukraine was in

a

  April 1970

b

 April 1979

c

 April 1983

d

 April 1986

Answer & Explanation
Answer : Option D

78.  Atoms of an element differ from those of all other elements in

a

  Atomic number and electronic configuration

b

 Atomic number and number of valence electrons

c

 Number of neutrons and electronic con- figuration

d

 Number of neutrons and number of valence electrons

Answer & Explanation
Answer : Option A

79.  Time taken by a radioactive substance to decay half is called

a

  half life

b

 time delay

c

 half period

d

 time constant

Answer & Explanation
Answer : Option A

80.  Radioactive decay is a change.

a

  nuclear

b

 physical

c

 chemical

d

 none of these

Answer & Explanation
Answer : Option A

81.  The credit of construction of first nuclear reactor goes to -

a

  Fermi

b

 Einstein

c

 Niels Bohr

d

 Oppenheimer

Answer & Explanation
Answer : Option A

82.  In gamma emission, change in nucleon number is

a

  zero

b

 definite

c

 increase by 1

d

 decreases by 1

Answer & Explanation
Answer : Option A

83.  Nuclides having the same atomic numbers are termed as

a

  isobars

b

 isomers

c

 isotopes

d

 isotones

Answer & Explanation
Answer : Option B

84.  Which one is radioactive in nature?

a

  Helium

b

 Tritium

c

 Deuterium

d

 Heavy hydrogen

Answer & Explanation
Answer : Option B

85.  Coolant present in the primary circuit of a pressurised water reactor is high pressure

a

  saturated steam

b

 saturated water

c

 sub cooled water

d

 superheated steam

Answer & Explanation
Answer : Option B

86.  Which of the following is used as a moderator in nuclear reactor?

a

  Radium

b

 Thorium

c

 Graphite

d

 Ordinary water

Answer & Explanation
Answer : Option C

87.  Thermal neutrons which are used to cause the fission of U-235 have energy_eV.

a

  < 0.025

b

 >1

c

 1-25

d

 > 200

Answer & Explanation
Answer : Option A

88.  According to Avogadro's Hypothesis, the smallest particle of an element or a compound, that can exist independently, is called

a

  An atom

b

 An anion

c

 A cation

d

 A molecule

Answer & Explanation
Answer : Option D

89.  Which of the following is not used as a nuclear fuel cladding material?

a

  Ceramics

b

 Zircalloy

c

 Cadmium

d

 Stainless steel

Answer & Explanation
Answer : Option C

90.  The velocity of thermal (slow) neutrons triggering nuclear fission reaction (having energy equal to 0.025 eV) is about metres/second.

a

  1100

b

 2200

c

 3300

d

 4400

Answer & Explanation
Answer : Option B
500
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