QCM : Nuclear Energy Principles and Reactions — 12 questions

Questions et réponses du QCM

1. What does mass-energy equivalence state about mass and energy?

Mass is measured in joules while energy is measured in kilograms
Mass and energy are unrelated physical quantities
Mass can be converted into energy and energy can be converted into mass
Energy can be converted into mass, but mass cannot become energy

Mass can be converted into energy and energy can be converted into mass

Explication

Mass-energy equivalence says that mass and energy can be transformed into one another. The relation is summarized by Einstein’s formula E = mc^2.

2. If 1.00 kg of mass is converted to energy, which expression gives the energy released using the rounded speed of light?

E = (1.00)(3.00 × 10^8)^2 J
E = (1.00)/(3.00 × 10^8)^2 J
E = (3.00 × 10^8)^2 / 1.00 J
E = (1.00)(3.00 × 10^8) J

E = (1.00)(3.00 × 10^8)^2 J

Explication

Using E = mc^2, the mass is multiplied by the square of the speed of light. With m = 1.00 kg and c ≈ 3.00 × 10^8 m/s, the correct setup is E = (1.00)(3.00 × 10^8)^2 J.

3. What is the mass defect of a nucleus?

The difference between the nucleus mass and the mass of an electron
The total mass of the protons and neutrons after binding
The energy needed to split the nucleus into protons and neutrons
The difference between the sum of the free nucleon masses and the mass of the assembled nucleus

The difference between the sum of the free nucleon masses and the mass of the assembled nucleus

Explication

Mass defect is defined as the difference between the masses of the separate nucleons and the mass of the bound nucleus. In the material, it is written as Δm = m_particles − m_noyau.

4. Why is a nucleus held together despite the electric repulsion between protons?

Protons lose their charge inside the nucleus
Gravity becomes dominant at nuclear distances
Neutrons eliminate all electric forces between protons
The strong nuclear force provides attraction at very short distance

The strong nuclear force provides attraction at very short distance

Explication

The strong nuclear force is the short-range आकर्षive force that binds nucleons together. It counteracts the electrostatic repulsion between positively charged protons.

5. For a deuterium nucleus, which pair of particles forms the nucleus described in the material?

One proton and one neutron
Two protons and no neutrons
Two neutrons and one proton
One proton and one electron

One proton and one neutron

Explication

Deuterium is hydrogen whose nucleus contains one proton and one neutron. The material identifies this nucleus as ²₁H.

6. Which statement correctly describes how the binding-related energy of deuterium is found?

By converting the deuterium mass defect with ΔE = Δm c^2
By multiplying the proton mass by the neutron mass
By subtracting the speed of light from the nuclear mass
By adding the masses of the proton and neutron without comparison

By converting the deuterium mass defect with ΔE = Δm c^2

Explication

The energy associated with deuterium binding comes from the mass defect turned into energy using ΔE = Δm c^2. The material also notes that the nucleus mass is smaller than the sum of the free nucleon masses.

7. What happens in alpha decay?

An unstable nucleus emits an alpha particle
A nucleus emits only gamma radiation
A proton is split into two neutrons
A light nucleus absorbs a neutron and becomes heavier

An unstable nucleus emits an alpha particle

Explication

Alpha decay is the radioactive decay process in which an unstable nucleus emits an alpha particle. The material identifies ²¹⁸₈₄Po as an alpha emitter.

8. How is the total energy released in alpha decay determined when the masses before and after decay are known?

Using the mass change in ΔE = Δm c^2
By dividing the mass change by c^2
By multiplying the final mass by the charge of the alpha particle
By adding the masses of all decay products

Using the mass change in ΔE = Δm c^2

Explication

The released decay energy is obtained from the mass difference through ΔE = Δm c^2. This is the same mass-to-energy relation used throughout the material.

9. Which reaction represents the fusion example given in the material?

H¹₁ + H¹₁ → He²₂
H²₁ + H³₁ → He⁴₂ + n¹₀
U²³⁵₉₂ + n¹₀ → Kr⁸⁹₃₆ + Ba¹⁴⁴₅₆ + 3n¹₀
Po²¹⁸₈₄ → He⁴₂ + Pb²¹⁴₈₂

H²₁ + H³₁ → He⁴₂ + n¹₀

Explication

The fusion reaction given is deuterium plus tritium producing helium-4 and a neutron. That is the explicit reactor example in the material.

10. In nuclear fusion, where does the released energy come from?

From the splitting of the final nucleus into smaller fragments
From the absorption of heat without any mass change
From the conversion of a small mass defect into energy
From electrons orbiting the fused nucleus

From the conversion of a small mass defect into energy

Explication

Fusion releases energy because the final products have slightly less mass than the initial nuclei, and the missing mass becomes energy. The material says this is calculated with ΔE = Δm c^2.

11. In a nuclear chain reaction, what does the multiplication factor n represent?

The average number of new fissions triggered by one fission
The minimum mass needed for a nucleus to undergo fission
The number of neutrons emitted by each uranium nucleus before splitting
The ratio between released energy and absorbed energy in the reactor

The average number of new fissions triggered by one fission

Explication

The multiplication factor n is defined as the average number of new fissions caused by one fission. It is not the number of neutrons themselves, but the number of subsequent fission events they trigger on average.

12. Why are neutrons slowed in water in a nuclear reactor before they induce further uranium fission?

Because slowing neutrons prevents any chain reaction from starting
Because slower neutrons are more able to cause additional uranium fission
Because water converts fission energy directly into electricity
Because water increases the mass defect of uranium nuclei

Because slower neutrons are more able to cause additional uranium fission

Explication

The source states that neutrons must be slowed in water before they can induce further uranium fission. Slower neutrons are more effective at sustaining the chain reaction, whereas the other options describe unrelated or opposite effects.

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Mémorisez les réponses avec 12 flashcards sur Nuclear Energy Principles and Reactions.

Mass-energy equivalence — formula?

E=mc^2

Nuclear binding — role?

Keeps nucleons together in nucleus.

Mass defect — definition?

Difference between nucleon sum and nucleus mass.

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