# Class 12 Physics MCQ – Nuclear Energy

This set of Class 12 Physics Chapter 13 Multiple Choice Questions & Answers (MCQs) focuses on “Nuclear Energy”.

1. Which of the following is an essential requirement for initiating the fusion reaction?
a) Critical mass
b) Thermal neutrons
c) High temperature
d) Critical temperature

Explanation: Two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles. High temperature is essential for initiating the fusion reaction. The others are not an essential requirement.

2. What is the reaction responsible for the production of light energy from the sun?
a) Fusion
b) Fission
c) Nuclear
d) Emission

Explanation: At very high temperatures in the interior of the sun, protons fuse to form helium nuclei, liberating a huge amount of energy. Therefore, the reaction responsible for the production of light energy from the sun is fusion.

3. What amount of energy is released by deuterium and tritium fusion?
a) 60.6 eV
b) 12.6 eV
c) 17.6 eV
d) 28.33 eV

Explanation: 1H2 + 1H32He4 + 0n1 + Q.
= [2.014 + 3.016 – 4.002 – 1.008] × 931.5 MeV.
= 17.6 MeV.

4. In a nuclear reaction, there is the conservation of which of the following?
a) Mass only
b) Energy only
c) Momentum only
d) Mass, energy, and momentum

Explanation: Two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles. In any nuclear reaction, mass, energy, and momentum are conserved. So, all three are conserved.

5. Nuclear fusion is possible in which of the following cases?
a) Only between light nuclei
b) Only between heavy nuclei
c) Between both light and heavy nuclei
d) Only between nuclei, which are stable against decay

Explanation: Nuclear fusion is possible between light nuclei. High temperature is essential for initiating the fusion reaction. Therefore, nuclear fusion is possible only between light nuclei and not between heavy nuclei.
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6. Solar energy is mainly caused due to fission of uranium present in the sun.
a) True
b) False

Explanation: No, this is a false statement. Solar energy is mainly caused due to the fusion of protons during the synthesis of heavier elements. So, it is not fission, but it is the fusion that results in solar energy.

7. Which of the following is used as a moderator in a nuclear reactor?
b) Plutonium
c) Uranium
d) Heavy water

Explanation: Heavy water is used as a moderator in a nuclear reactor. It slows down neutrons and also has a low probability of absorption of neutrons. The other options are not valid.

8. In nuclear reactors, what are the controlling rods made of?
b) Graphite
c) Stainless steel
d) Plutonium

Explanation: In nuclear reactors, cadmium rods are used as control rods. They are used to absorb the extra nucleons and to absorb neutrons, making them unavailable to cause fission. The other options are not valid.

9. The operation of a nuclear reactor is said to be critical if the multiplication factor (k) has a value of what?
a) 1
b) 0
c) 1.5
d) 2.1

Explanation: For a nuclear reactor, k = 1. It is the ratio of the number of neutrons produced in a nuclear pile to the number disappearing that must equal to unity for a chain reaction.

10. A neutron can cause fission in which of the following?
a) Hydrogen
b) Uranium-235
c) Thorium
d) Uranium-238

Explanation: A neutron, irrespective of whether it is slow or fast, can cause fission in a Uranium 235 nuclei. It absorbs a neutron and fissions into two new atoms by releasing some binding energy.

Sanfoundry Global Education & Learning Series – Physics – Class 12.

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