{"id":12677,"date":"2025-09-20T08:07:13","date_gmt":"2025-09-20T07:07:13","guid":{"rendered":"https:\/\/mcqsadda.com\/?p=12677"},"modified":"2025-10-22T10:02:20","modified_gmt":"2025-10-22T09:02:20","slug":"nuclear-fission-and-fusion-top-100-mcqs-with-answer-and-explanation","status":"publish","type":"post","link":"https:\/\/mcqsadda.com\/index.php\/2025\/09\/20\/nuclear-fission-and-fusion-top-100-mcqs-with-answer-and-explanation\/","title":{"rendered":"Nuclear fission and fusion Top 100 MCQs With Answer and Explanation"},"content":{"rendered":"\n

1. Who discovered nuclear fission?<\/mark><\/strong>
a) Hahn & Strassmann
b) Einstein
c) Rutherford
d) Curie
Answer:<\/strong> a
Explanation:<\/strong> Otto Hahn and Fritz Strassmann (1938) discovered splitting of U-235 by neutrons.<\/p>\n\n\n\n

2. Nuclear fission occurs when:<\/mark><\/strong>
a) Heavy nucleus splits into smaller nuclei
b) Small nuclei combine
c) Atom ionizes
d) Proton decays
Answer:<\/strong> a
Explanation:<\/strong> Fission releases energy due to mass defect.<\/p>\n\n\n\n

3. The first controlled nuclear chain reaction was by:<\/mark><\/strong>
a) Enrico Fermi
b) Rutherford
c) Einstein
d) Bohr
Answer:<\/strong> a
Explanation:<\/strong> Fermi (1942) achieved controlled fission in Chicago Pile-1.<\/p>\n\n\n\n

4. Nuclear fission releases energy because:<\/mark><\/strong>
a) Mass of products < mass of reactants
b) Mass increases
c) No mass change
d) Proton decays
Answer:<\/strong> a
Explanation:<\/strong> Mass defect converts to energy via .<\/p>\n\n\n\n

5. Fission is induced by:<\/mark><\/strong>
a) Neutron absorption
b) Proton absorption
c) Electron capture
d) Gamma rays only
Answer:<\/strong> a
Explanation:<\/strong> Thermal neutrons induce fission in U-235.<\/p>\n\n\n\n

6. Fission of U-235 by thermal neutron produces:<\/mark><\/strong>
a) Two fission fragments + neutrons + energy
b) Only energy
c) Only neutrons
d) Alpha particles
Answer:<\/strong> a
Explanation:<\/strong> Typical fission releases ~200 MeV energy.<\/p>\n\n\n\n

7. Typical energy released in fission of 1 U-235 nucleus:<\/mark><\/strong>
a) ~200 MeV
b) 1 MeV
c) 10 MeV
d) 1 GeV
Answer:<\/strong> a
Explanation:<\/strong> Energy comes from mass defect of nucleus.<\/p>\n\n\n\n

8. Heavy elements that can undergo fission:<\/mark><\/strong>
a) U-235, Pu-239
b) H-1, H-2
c) He-4, Li-6
d) C-12
Answer:<\/strong> a
Explanation:<\/strong> Only heavy, fissile isotopes split easily with neutrons.<\/p>\n\n\n\n

9. Fission fragments are usually:<\/mark><\/strong>
a) Radioactive
b) Stable
c) Neutral
d) Alpha particles
Answer:<\/strong> a
Explanation:<\/strong> Fission products like Sr-90, Cs-137 are radioactive.<\/p>\n\n\n\n

10. Average number of neutrons released per fission of U-235:<\/mark><\/strong>
a) 2\u20133
b) 1
c) 5
d) 0
Answer:<\/strong> a
Explanation:<\/strong> These neutrons can sustain chain reaction.<\/p>\n\n\n\n

11. Spontaneous fission occurs:<\/mark><\/strong>
a) Without external neutron
b) Only with neutron
c) Only with gamma
d) Never
Answer:<\/strong> a
Explanation:<\/strong> Some heavy nuclei (e.g., Cf-252) fission spontaneously.<\/p>\n\n\n\n

12. Fissile materials:<\/mark><\/strong>
a) U-235, Pu-239
b) U-238, Th-232
c) He-4
d) Li-7
Answer:<\/strong> a
Explanation:<\/strong> Can sustain chain reaction with thermal neutrons.<\/p>\n\n\n\n

13. Fertile materials:<\/mark><\/strong>
a) U-238, Th-232
b) U-235
c) Pu-239
d) H-2
Answer:<\/strong> a
Explanation:<\/strong> Can convert to fissile isotopes by neutron absorption.<\/p>\n\n\n\n

14. Fast neutrons in fission are slowed by:<\/mark><\/strong>
a) Moderator
b) Control rods
c) Shielding
d) Coolant
Answer:<\/strong> a
Explanation:<\/strong> Materials like water, graphite reduce neutron speed.<\/p>\n\n\n\n

15. Mass defect in fission is:<\/mark><\/strong>
a) Converted to energy
b) Converted to matter
c) Lost
d) Zero
Answer:<\/strong> a
Explanation:<\/strong> Energy released calculated by .<\/p>\n\n\n\n

16. First nuclear bomb used<\/mark><\/strong>:
a) U-235 and Pu-239
b) U-238 only
c) H-2
d) Li-6 only
Answer:<\/strong> a
Explanation:<\/strong> “Little Boy” used U-235; “Fat Man” used Pu-239.<\/p>\n\n\n\n

17. Fission reaction can be:<\/mark><\/strong>
a) Controlled (reactor) or uncontrolled (bomb)
b) Only controlled
c) Only uncontrolled
d) Impossible
Answer:<\/strong> a
Explanation:<\/strong> Rate of neutron multiplication distinguishes reactor and bomb.<\/p>\n\n\n\n

18. Critical mass depends on:<\/mark><\/strong>
a) Material, shape, purity
b) Color
c) Temperature only
d) Pressure only
Answer:<\/strong> a
Explanation:<\/strong> Spherical, pure fissile material lowers critical mass.<\/p>\n\n\n\n

19. Supercritical mass means:<\/mark><\/strong>
a) Chain reaction increases
b) Reaction stops
c) Stable
d) Slow reaction
Answer:<\/strong> a
Explanation:<\/strong> More than critical mass leads to exponential neutron multiplication.<\/p>\n\n\n\n

20. Moderator slows neutrons but does not:<\/mark><\/strong>
a) Absorb neutrons significantly
b) Increase temperature
c) Reflect neutrons
d) Produce fission
Answer:<\/strong> a
Explanation:<\/strong> Slow neutrons enhance fission probability without absorption.<\/p>\n\n\n\n

21. Neutron reflector in reactors:
<\/mark><\/strong>a) Bounces back escaping neutrons
b) Absorbs neutrons
c) Emits gamma rays
d) Produces energy
Answer:<\/strong> a
Explanation:<\/strong> Increases neutron economy and reduces critical mass.<\/p>\n\n\n\n

22. Uranium-238 is<\/strong>:<\/mark>
a) Fertile
b) Fissile
c) Stable
d) Radioactive only
Answer:<\/strong> a
Explanation:<\/strong> Absorbs neutron \u2192 Pu-239 fissile material.<\/p>\n\n\n\n

23. Plutonium-239 is obtained by:<\/mark><\/strong>
a) Neutron capture in U-238
b) Beta decay of U-235
c) Fusion of H-2
d) Direct extraction from nature
Answer:<\/strong> a
Explanation:<\/strong> .<\/p>\n\n\n\n

24. Fission product yields:<\/mark><\/strong>
a) Random nuclei
b) Only alpha particles
c) Only neutrons
d) Only gamma
Answer:<\/strong> a
Explanation:<\/strong> Fission splits nucleus into unequal fragments with neutrons emitted.<\/p>\n\n\n\n

25. Fission of U-235 produces most energy as:<\/mark><\/strong>
a) Kinetic energy of fission fragments
b) Neutrons
c) Gamma only
d) Beta only
Answer:<\/strong> a
Explanation:<\/strong> ~85% energy carried by fragment kinetic energy; rest by neutrons\/gamma.<\/p>\n\n\n\n

26. Chain reaction occurs when:<\/mark><\/strong>
a) Neutrons from one fission induce further fissions
b) Protons collide
c) Electrons escape
d) Alpha particles emitted
Answer:<\/strong> a
Explanation:<\/strong> Released neutrons trigger further fissions, sustaining reaction.<\/p>\n\n\n\n

27. Controlled chain reaction is used in:<\/mark><\/strong>
a) Nuclear reactors
b) Bombs
c) Stars
d) Solar cells
Answer:<\/strong> a
Explanation:<\/strong> Neutron population is regulated to release steady energy.<\/p>\n\n\n\n

28. Uncontrolled chain reaction is:<\/mark><\/strong>
a) Nuclear explosion
b) Nuclear power
c) Solar fusion
d) Chemical reaction
Answer:<\/strong> a
Explanation:<\/strong> Rapid multiplication of neutrons causes massive energy release.<\/p>\n\n\n\n

29. Moderator in reactor:<\/mark><\/strong>
a) Slows down neutrons
b) Absorbs neutrons
c) Increases neutron speed
d) Produces energy
Answer:<\/strong> a
Explanation:<\/strong> Slow neutrons are more likely to induce fission in U-235.<\/p>\n\n\n\n

30. Examples of moderators:<\/mark><\/strong>
a) Heavy water, graphite, light water
b) Lead, cadmium
c) Uranium-238
d) Plutonium
Answer:<\/strong> a
Explanation:<\/strong> Non-absorbing substances that slow down neutrons.<\/p>\n\n\n\n

31. Control rods absorb:<\/mark><\/strong>
a) Excess neutrons
b) Energy
c) Heat
d) Protons
Answer:<\/strong> a
Explanation:<\/strong> Made of cadmium, boron, or hafnium to control chain reaction.<\/p>\n\n\n\n

32. Coolant in reactor is used to:<\/mark><\/strong>
a) Remove heat from core
b) Reflect neutrons
c) Produce neutrons
d) Absorb radiation
Answer:<\/strong> a
Explanation:<\/strong> Circulates heat to generate steam for electricity.<\/p>\n\n\n\n

33. Fast neutron reactors:<\/mark><\/strong>
a) Use fast neutrons without moderator
b) Use thermal neutrons
c) Absorb neutrons only
d) Use chemical energy
Answer:<\/strong> a
Explanation:<\/strong> No moderator needed; fuel enriched for fast fission.<\/p>\n\n\n\n

34. Breeder reactor converts:<\/mark><\/strong>
a) Fertile U-238 \u2192 Fissile Pu-239
b) Pu-239 \u2192 U-238
c) H-2 \u2192 He-3
d) None
Answer:<\/strong> a
Explanation:<\/strong> Produces more fissile material than consumed.<\/p>\n\n\n\n

35. Criticality means:<\/mark><\/strong>
a) Chain reaction is self-sustaining
b) Reaction stops
c) Neutrons absorbed completely
d) Mass is stable
Answer:<\/strong> a
Explanation:<\/strong> Number of neutrons causing fissions balances those lost.<\/p>\n\n\n\n

36. Subcritical mass:<\/mark><\/strong>
a) Reaction dies out
b) Reaction increases
c) Reaction steady
d) Explosive
Answer:<\/strong> a
Explanation:<\/strong> Not enough fissile material for chain reaction.<\/p>\n\n\n\n

37. Supercritical mass:<\/mark><\/strong>
a) Reaction accelerates
b) Reaction steady
c) Reaction stops
d) None
Answer:<\/strong> a
Explanation:<\/strong> Mass exceeds critical \u2192 exponential increase in fissions.<\/p>\n\n\n\n

38. Energy produced per fission of U-235:<\/mark><\/strong>
a) ~200 MeV
b) 1 MeV
c) 10 MeV
d) 1000 MeV
Answer:<\/strong> a
Explanation:<\/strong> Majority released as kinetic energy of fragments.<\/p>\n\n\n\n

39. Neutrons released per fission:<\/mark><\/strong>
a) 2\u20133
b) 1
c) 5\u20136
d) 0
Answer:<\/strong> a
Explanation:<\/strong> These neutrons sustain chain reaction.<\/p>\n\n\n\n

40. Thermal neutrons have energy:<\/mark><\/strong>
a) ~0.025 eV
b) 1 MeV
c) 100 keV
d) 10 MeV
Answer:<\/strong> a
Explanation:<\/strong> Neutrons in equilibrium with room temperature (~25 meV).<\/p>\n\n\n\n

41. Fast neutrons have energy:<\/mark><\/strong>
a) 1\u20132 MeV
b) 0.025 eV
c) 1 eV
d) 10 meV
Answer:<\/strong> a
Explanation:<\/strong> Produced directly from fission, need slowing by moderator.<\/p>\n\n\n\n

42. Uranium enrichment increases:<\/mark><\/strong>
a) U-235 fraction
b) U-238 fraction
c) Pu-239 fraction
d) None
Answer:<\/strong> a
Explanation:<\/strong> Enrichment increases fissile isotope content for reactor\/bomb use.<\/p>\n\n\n\n

43. Natural uranium contains:<\/mark><\/strong>
a) 0.7% U-235, 99.3% U-238
b) 50% U-235
c) 100% U-238
d) 10% Pu-239
Answer:<\/strong> a
Explanation:<\/strong> Low fissile fraction requires enrichment for reactors.<\/p>\n\n\n\n

44. Pressurized water reactor (PWR) uses:<\/mark><\/strong>
a) Water as coolant and moderator
b) Graphite as moderator
c) Heavy water only
d) Air cooling
Answer:<\/strong> a
Explanation:<\/strong> Pressurized water prevents boiling, transfers heat to turbine.<\/p>\n\n\n\n

45. Boiling water reactor (BWR):<\/mark><\/strong>
a) Water boils in core \u2192 steam directly drives turbine
b) Uses graphite
c) Uses heavy water
d) No water
Answer:<\/strong> a
Explanation:<\/strong> Steam generated in core goes directly to turbines.<\/p>\n\n\n\n

46. CANDU reactor uses:<\/mark><\/strong>
a) Heavy water moderator and coolant
b) Light water
c) Graphite
d) Gas
Answer:<\/strong> a
Explanation:<\/strong> Uses natural uranium; heavy water enhances neutron economy.<\/p>\n\n\n\n

47. Fast breeder reactors produce:<\/mark><\/strong>
a) More fissile material than consumed
b) Less
c) Equal
d) None
Answer:<\/strong> a
Explanation:<\/strong> Fertile U-238 \u2192 Pu-239 conversion.<\/p>\n\n\n\n

48. Nuclear reactor safety involves:<\/mark><\/strong>
a) Control rods, containment, cooling
b) Only shielding
c) Only moderators
d) None
Answer:<\/strong> a
Explanation:<\/strong> Ensures controlled reaction, prevents meltdown, protects environment.<\/p>\n\n\n\n

49. Fission produces:<\/mark><\/strong>
a) Neutrons, gamma, energy, radioactive fragments
b) Only energy
c) Only gamma
d) Only neutrons
Answer:<\/strong> a
Explanation:<\/strong> Multiple products released; fragments radioactive.<\/p>\n\n\n\n

50. Nuclear waste is mainly:<\/mark><\/strong>
a) Fission products
b) Uranium only
c) Water
d) Moderator
Answer:<\/strong> a
Explanation:<\/strong> Radioactive isotopes like Cs-137, Sr-90, Tc-99 are hazardous.<\/p>\n\n\n\n

51. Nuclear fusion is the process of:<\/mark><\/strong>
a) Light nuclei combining to form heavier nucleus
b) Heavy nuclei splitting
c) Electron capture
d) Proton decay
Answer:<\/strong> a
Explanation:<\/strong> Fusion releases energy due to mass defect, opposite of fission.<\/p>\n\n\n\n

52. Fusion requires:<\/mark><\/strong>
a) Extremely high temperature and pressure
b) Low temperature
c) Normal pressure
d) Neutron absorption only
Answer:<\/strong> a
Explanation:<\/strong> Overcomes electrostatic repulsion (Coulomb barrier) between nuclei.<\/p>\n\n\n\n

53. Fusion in stars primarily converts:<\/mark><\/strong>
a) Hydrogen \u2192 Helium
b) Uranium \u2192 Lead
c) Helium \u2192 Hydrogen
d) Carbon \u2192 Oxygen
Answer:<\/strong> a
Explanation:<\/strong> Proton-proton chain and CNO cycle fuse H into He, releasing energy.<\/p>\n\n\n\n

54. Energy released in fusion comes from:<\/mark><\/strong>
a) Mass defect \u2192 E = \u0394m c\u00b2
b) Neutron absorption
c) Alpha decay
d) Electron capture
Answer:<\/strong> a
Explanation:<\/strong> Mass of product < sum of reactants; energy released as radiation and kinetic energy.<\/p>\n\n\n\n

55. Temperature required for fusion of H isotopes:<\/mark><\/strong>
a) ~10\u2077\u201310\u2078 K
b) Room temperature
c) 1000 K
d) 0 K
Answer:<\/strong> a
Explanation:<\/strong> Extreme temperature needed to overcome Coulomb repulsion.<\/p>\n\n\n\n

56. Deuterium-deuterium fusion reaction produces:<\/mark><\/strong>
a) Helium-3 + neutron or tritium + proton
b) Only helium
c) Alpha particle only
d) Neutron only
Answer:<\/strong> a
Explanation:<\/strong> Fusion of D nuclei has two possible branches releasing energy.<\/p>\n\n\n\n

57. Deuterium-tritium (D-T) fusion reaction releases:<\/mark><\/strong>
a) ~17.6 MeV energy
b) 200 MeV
c) 1 MeV
d) 100 MeV
Answer:<\/strong> a
Explanation:<\/strong> Most promising reaction for fusion reactors.<\/p>\n\n\n\n

58. Fusion produces more energy per unit mass than fission:<\/mark><\/strong>
a) True
b) False
Answer:<\/strong> a
Explanation:<\/strong> Energy density of fusion (H \u2192 He) is much higher than U-235 fission.<\/p>\n\n\n\n

59. Fusion requires confinement:<\/mark><\/strong>
a) Magnetic or inertial
b) Chemical
c) Thermal only
d) Electric only
Answer:<\/strong> a
Explanation:<\/strong> Plasma must be confined at high temperature for fusion to occur.<\/p>\n\n\n\n

60. Stars shine due to:<\/mark><\/strong>
a) Nuclear fusion in core
b) Fission reactions
c) Chemical reactions
d) Gravitational collapse only
Answer:<\/strong> a
Explanation:<\/strong> Fusion of hydrogen to helium produces photons, light, and heat.<\/p>\n\n\n\n

61. Proton-proton chain is dominant in:<\/mark><\/strong>
a) Sun-like stars
b) Massive stars
c) White dwarfs
d) Neutron stars
Answer:<\/strong> a
Explanation:<\/strong> Fusion of H \u2192 He in low-mass stars mainly via proton-proton chain.<\/p>\n\n\n\n

62. CNO cycle is dominant in:<\/mark><\/strong>
a) Massive stars (>1.3 solar masses)
b) Sun
c) White dwarfs
d) All stars equally
Answer:<\/strong> a
Explanation:<\/strong> Carbon acts as catalyst in hydrogen fusion in massive stars.<\/p>\n\n\n\n

63. Helium burning in stars produces:<\/mark><\/strong>
a) Carbon and oxygen
b) Hydrogen
c) Nitrogen
d) Neon
Answer:<\/strong> a
Explanation:<\/strong> Fusion of 3 He nuclei \u2192 C-12, also produces O-16 via \u03b1-capture.<\/p>\n\n\n\n

64. Fusion reactions in stars are exothermic because:<\/mark><\/strong>
a) Binding energy per nucleon increases
b) Decreases
c) Remains same
d) None
Answer:<\/strong> a
Explanation:<\/strong> Products are more tightly bound \u2192 energy released.<\/p>\n\n\n\n

65. Energy transport in stars occurs via:<\/mark><\/strong>
a) Radiation, convection, conduction
b) Only radiation
c) Only conduction
d) Only convection
Answer:<\/strong> a
Explanation:<\/strong> Core energy moves outward by radiation or convection depending on opacity.<\/p>\n\n\n\n

66. Fusion reactions produce:<\/mark><\/strong>
a) Neutrinos
b) Photons
c) Kinetic energy of particles
d) All of the above
Answer:<\/strong> d
Explanation:<\/strong> Energy appears in multiple forms, detectable by solar neutrinos.<\/p>\n\n\n\n

67. Sun\u2019s core temperature:<\/mark><\/strong>
a) ~1.5 \u00d7 10\u2077 K
b) 10\u2074 K
c) 10\u2075 K
d) 10\u2076 K
Answer:<\/strong> a
Explanation:<\/strong> High enough for proton-proton fusion chain.<\/p>\n\n\n\n

68. Lawson criterion defines:<\/mark><\/strong>
a) Condition for energy gain in fusion
b) Condition for fission
c) Neutron lifetime
d) Alpha decay rate
Answer:<\/strong> a
Explanation:<\/strong> Product of plasma density, confinement time, and temperature must exceed critical value.<\/p>\n\n\n\n

69. Tokamak uses:<\/mark><\/strong>
a) Magnetic confinement
b) Laser confinement
c) Chemical confinement
d) None
Answer:<\/strong> a
Explanation:<\/strong> Toroidal magnetic field confines hot plasma for fusion experiments.<\/p>\n\n\n\n

70. Inertial confinement fusion uses:<\/mark><\/strong>
a) Lasers or ion beams to compress fuel pellet
b) Magnetic field
c) Gas cooling
d) Chemical explosives
Answer:<\/strong> a
Explanation:<\/strong> Rapid compression heats plasma to fusion temperatures briefly.<\/p>\n\n\n\n

71. Deuterium in fusion reactors is obtained from:<\/mark><\/strong>
a) Sea water
b) Uranium ore
c) Graphite
d) Lead
Answer:<\/strong> a
Explanation:<\/strong> D\/H ratio in water is sufficient for fusion fuel.<\/p>\n\n\n\n

72. Tritium in reactors is produced by:<\/mark><\/strong>
a) Lithium + neutron \u2192 Tritium + Helium
b) Deuterium only
c) Uranium decay
d) Fission of Pu
Answer:<\/strong> a
Explanation:<\/strong> Tritium is rare naturally; produced in situ via Li-6 reactions.<\/p>\n\n\n\n

73. Energy released per gram of fusion fuel is:<\/mark><\/strong>
a) ~10\u2077 times chemical energy
b) Same as chemical
c) Less
d) Zero
Answer:<\/strong> a
Explanation:<\/strong> Extremely high energy density per mass of hydrogen isotopes.<\/p>\n\n\n\n

74. Fusion in stars maintains:<\/mark><\/strong>
a) Hydrostatic equilibrium
b) Nuclear fission
c) Chemical balance
d) Magnetic equilibrium
Answer:<\/strong> a
Explanation:<\/strong> Outward radiation pressure balances gravitational pull.<\/p>\n\n\n\n

75. Fusion reactions are considered:<\/mark><\/strong>
a) Clean energy source
b) Polluting
c) Radioactive only
d) Chemical
Answer:<\/strong> a
Explanation:<\/strong> Minimal radioactive waste, no greenhouse gases.<\/p>\n\n\n\n

76. Fusion reactors aim to use which reaction first commercially?<\/mark><\/strong>
a) Deuterium\u2013Tritium (D-T) fusion
b) Deuterium\u2013Deuterium (D-D) fusion
c) Proton\u2013Proton fusion
d) Carbon\u2013Nitrogen fusion
Answer:<\/strong> a
Explanation:<\/strong> D-T reaction has highest cross-section at achievable temperatures (~100 million K).<\/p>\n\n\n\n

77. Energy released in D-T fusion per reaction:<\/mark><\/strong>
a) 17.6 MeV
b) 200 MeV
c) 1 MeV
d) 100 MeV
Answer:<\/strong> a
Explanation:<\/strong> 3.5 MeV carried by alpha, 14.1 MeV by neutron.<\/p>\n\n\n\n

78. Fusion fuel advantage over fission:<\/mark><\/strong>
a) Abundant, less radioactive waste
b) Scarce fuel
c) More long-lived waste
d) Difficult to obtain
Answer:<\/strong> a
Explanation:<\/strong> Deuterium abundant in sea water; Tritium can be bred; minimal long-lived waste.<\/p>\n\n\n\n

79. Fission vs. Fusion: Energy per kg:<\/mark><\/strong>
a) Fusion > Fission > Chemical
b) Fission > Fusion
c) Chemical > Fusion
d) Fission = Fusion
Answer:<\/strong> a
Explanation:<\/strong> Fusion releases ~10\u2077 times chemical energy; Fission ~10\u2076 times.<\/p>\n\n\n\n

80. Stellar nucleosynthesis produces elements:<\/mark><\/strong>
a) H \u2192 He \u2192 C \u2192 O \u2192 Fe
b) Only H \u2192 He
c) Only Fe
d) None
Answer:<\/strong> a
Explanation:<\/strong> Fusion in stars forms heavier elements until iron, beyond which fusion is endothermic.<\/p>\n\n\n\n

81. Hydrogen bombs use:<\/mark><\/strong>
a) Fission + Fusion (Teller-Ulam design)
b) Fission only
c) Fusion only
d) Chemical explosive
Answer:<\/strong> a
Explanation:<\/strong> Fission primary compresses fusion fuel to trigger D-T fusion.<\/p>\n\n\n\n

82. Magnetic confinement fusion device:<\/mark><\/strong>
a) Tokamak
b) Nuclear reactor
c) Bubble chamber
d) Cloud chamber
Answer:<\/strong> a
Explanation:<\/strong> Magnetic fields confine plasma at millions of K.<\/p>\n\n\n\n

83. Inertial confinement fusion uses:<\/mark><\/strong>
a) High-power lasers
b) Magnetic fields
c) Chemical reactions
d) Nuclear fission
Answer:<\/strong> a
Explanation:<\/strong> Laser energy compresses fuel pellet to achieve necessary temperature & pressure.<\/p>\n\n\n\n

84. Tritium breeding reaction in fusion:<\/mark><\/strong>
a) Li-6 + n \u2192 T + He-4
b) H-2 + n \u2192 T
c) He-3 + n \u2192 T
d) U-238 + n \u2192 T
Answer:<\/strong> a
Explanation:<\/strong> Essential to sustain D-T fuel cycle in reactors.<\/p>\n\n\n\n

85. Fusion reactors face main challenge:<\/mark><\/strong>
a) Achieving confinement, temperature, and density simultaneously
b) Fuel scarcity
c) Waste disposal
d) Low energy output
Answer:<\/strong> a
Explanation:<\/strong> Plasma confinement at extreme conditions is technologically difficult.<\/p>\n\n\n\n

86. Energy gain factor (Q) in fusion:<\/mark><\/strong>
a) Ratio of fusion power output to power input
b) Efficiency of fission
c) Efficiency of chemical reaction
d) None
Answer:<\/strong> a
Explanation:<\/strong> Q > 1 needed for net energy gain.<\/p>\n\n\n\n

87. ITER project aims at:<\/mark><\/strong>
a) Demonstrating net energy gain from D-T fusion
b) Fission reactor efficiency
c) Solar power
d) Chemical battery
Answer:<\/strong> a
Explanation:<\/strong> International Thermonuclear Experimental Reactor; Tokamak design.<\/p>\n\n\n\n

88. Advantages of fusion over fission:<\/mark><\/strong>
a) More energy per kg, abundant fuel, safer, less long-lived waste
b) Less energy
c) Less safe
d) Rare fuel
Answer:<\/strong> a
Explanation:<\/strong> Fusion has higher energy density and minimal long-lived radioactive products.<\/p>\n\n\n\n

89. Disadvantage of fission over fusion:<\/mark><\/strong>
a) Radioactive waste
b) Requires high temperature
c) Fuel abundant
d) Minimal radiation
Answer:<\/strong> a
Explanation:<\/strong> Fission produces long-lived fission products.<\/p>\n\n\n\n

90. Helium-3 fusion is considered:<\/mark><\/strong>
a) Aneutronic, cleaner reaction
b) Produces many neutrons
c) Produces long-lived waste
d) Not energy efficient
Answer:<\/strong> a
Explanation:<\/strong> \u00b3He + D \u2192 \u2074He + proton; minimal neutron emission \u2192 cleaner.<\/p>\n\n\n\n

91. Fusion reactor plasma is typically:<\/mark><\/strong>
a) Fully ionized gas (plasma)
b) Solid
c) Liquid
d) Gas only
Answer:<\/strong> a
Explanation:<\/strong> High temperature ionizes fuel, forming plasma for fusion reactions.<\/p>\n\n\n\n

92. Lawson criterion states:<\/mark><\/strong>
a) n \u03c4 T \u2265 critical value for net energy gain
b) Critical mass for fission
c) Energy released in fission
d) Temperature of sun
Answer:<\/strong> a
Explanation:<\/strong> Product of density (n), confinement time (\u03c4), and temperature (T) must exceed threshold.<\/p>\n\n\n\n

93. Fusion in stars vs. reactors:<\/mark><\/strong>
a) Stars: gravitational confinement, reactors: magnetic\/inertial
b) Both chemical
c) Stars fission only
d) Both magnetic
Answer:<\/strong> a
Explanation:<\/strong> Gravity in stars substitutes for confinement; reactors need artificial confinement.<\/p>\n\n\n\n

94. Energy released in one gram of D-T fuel:<\/mark><\/strong>
a) ~340 GJ
b) 1 MJ
c) 1 GJ
d) 1 kJ
Answer:<\/strong> a
Explanation:<\/strong> Extremely high energy density compared to chemical fuels.<\/p>\n\n\n\n

95. Fission vs Fusion: Waste type<\/mark><\/strong>
a) Fusion \u2192 short-lived, fission \u2192 long-lived
b) Both same
c) Fusion \u2192 long-lived
d) Fission \u2192 short-lived
Answer:<\/strong> a
Explanation:<\/strong> Fusion products mostly short-lived; fission products like Cs-137 last decades.<\/p>\n\n\n\n

96. Tritium handling in fusion:<\/mark><\/strong>
a) Requires containment due to radioactivity
b) Stable, no containment
c) Solid fuel only
d) Non-radioactive
Answer:<\/strong> a
Explanation:<\/strong> Beta emitter; precautions needed for environmental safety.<\/p>\n\n\n\n

97. Fusion energy advantage for space:<\/mark><\/strong>
a) High energy density, less mass
b) Low energy
c) Produces chemical waste
d) Requires fission
Answer:<\/strong> a
Explanation:<\/strong> Efficient, minimal fuel mass for spacecraft propulsion.<\/p>\n\n\n\n

98. Stellar evolution ends when:<\/mark><\/strong>
a) Core iron forms, fusion stops
b) Hydrogen exhausted only
c) Carbon burns completely
d) Stars explode randomly
Answer:<\/strong> a
Explanation:<\/strong> Iron fusion is endothermic \u2192 star collapses \u2192 supernova or white dwarf.<\/p>\n\n\n\n

99. Neutron flux in fission reactor:<\/mark><\/strong>
a) Determines reaction rate
b) Determines fuel mass only
c) Determines temperature only
d) Not important
Answer:<\/strong> a
Explanation:<\/strong> Higher flux \u2192 more fission events per second.<\/p>\n\n\n\n

100. Comparison summary:<\/mark><\/strong>
a) Fusion: cleaner, more energy, abundant fuel; Fission: radioactive waste, limited fuel
b) Fusion: less energy; Fission: more energy
c) Both same
d) None
Answer:<\/strong> a
Explanation:<\/strong> Fusion is ultimate goal for clean energy; fission currently commercial but has waste issues.<\/p>\n","protected":false},"excerpt":{"rendered":"

1. Who discovered nuclear fission?a) Hahn & Strassmannb) Einsteinc) Rutherfordd) CurieAnswer: aExplanation: Otto Hahn and Fritz Strassmann (1938) discovered splitting of U-235 by neutrons. 2. Nuclear fission occurs when:a) Heavy nucleus splits into smaller nucleib) Small nuclei combinec) Atom ionizesd) Proton decaysAnswer: aExplanation: Fission releases energy due to mass defect. 3. The first controlled nuclear<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8,19],"tags":[15808,15798,15806,15481,15810,15813,15807,15814,15809,4029,5649,15465,5623,15811,15800,15751,10960,15746,15743,15812,15758,15749,15536,15479,15474,15467,15483,15472,15592,15456,15478,15752,15469,15480],"class_list":{"0":"post-12677","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-physics","7":"category-science","8":"tag-atomic-energy","9":"tag-atomic-nucleus","10":"tag-chain-reaction","11":"tag-competitive-exam-physics","12":"tag-energy-from-nucleus","13":"tag-fission-process","14":"tag-fission-reactor","15":"tag-fusion-process","16":"tag-fusion-reactor","17":"tag-mcqs-adda","18":"tag-mcqs-for-pc-psi-sda-fda-pdo-vao-banking-kas-ias-ssc-gd-ssc-chsl-ssc-cgl-for-all-compitative-exams","19":"tag-mcqs-for-physics-exam","20":"tag-mcqs-for-sda-fda-pdo-vao-banking-kas-ias-ssc-gd-ssc-chsl-ssc-cgl-for-all-compitative-exams","21":"tag-nuclear-applications","22":"tag-nuclear-energy","23":"tag-nuclear-fission","24":"tag-nuclear-fission-and-fusion-top-100-mcqs-with-answer-and-explanation","25":"tag-nuclear-fusion","26":"tag-nuclear-physics","27":"tag-nuclear-power","28":"tag-nuclear-problems","29":"tag-nuclear-reactions","30":"tag-physics-formulas","31":"tag-physics-learning","32":"tag-physics-mcqs","33":"tag-physics-preparation-material","34":"tag-physics-questions-and-answers","35":"tag-physics-quiz","36":"tag-physics-revision","37":"tag-physics-study-material","38":"tag-psc-physics-mcqs","39":"tag-radioactivity","40":"tag-ssc-physics-mcqs","41":"tag-upsc-physics-mcqs"},"_links":{"self":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12677","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/comments?post=12677"}],"version-history":[{"count":4,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12677\/revisions"}],"predecessor-version":[{"id":12734,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/posts\/12677\/revisions\/12734"}],"wp:attachment":[{"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/media?parent=12677"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/categories?post=12677"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mcqsadda.com\/index.php\/wp-json\/wp\/v2\/tags?post=12677"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}