IB Physics Topic E.5.1 Nuclear Fusion in Stars Revision Notes (SL/HL)

IB Physics Topic E.5.1 Nuclear Fusion in Stars Revision Notes (SL/HL) | RevisionDojo

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Nuclear Fusion: The Power Behind Stars

Deuterium-Tritium Fusion

Consider the fusion of deuterium ($ ^2\text{H} $) and tritium ($ ^3\text{H} $): $$^2\text{H} + ^3\text{H} \rightarrow ^4\text{He} + ^1\text{n}$$
In this reaction, a helium nucleus ($ ^4\text{He} $) and a neutron ($ ^1\text{n} $) are produced.
The mass of the reactants is slightly greater than the mass of the products, and this mass difference ($ \Delta m $) is converted into energy: $$Q = \Delta m c^2$$
For this reaction, the energy released is approximately 17.6 MeV (million electron volts) per fusion event, an immense amount of energy at the atomic scale.

Example question

Calculate the energy released in the reaction $^2\text{H} + ^3\text{H} \rightarrow ^4\text{He} + ^1\text{n}$, given the following atomic masses:

$^2\text{H}$: 2.014102 u
$^3\text{H}$: 3.016049 u
$^4\text{He}$: 4.002602 u
$^1\text{n}$: 1.008665 u

Solution

The mass defect is: $$\Delta m = (2.014102 + 3.016049) - (4.002602 + 1.008665) = 0.018884\,\text{u}$$
Convert this mass into energy using $1\,\text{u} = 931.5\,\text{MeV}\,c^{-2}$: $$Q = \Delta m c^2 = 0.018884 \times 931.5 = 17.6\,\text{MeV}$$

Active recall

What is the role of the mass defect in determining the energy released during nuclear fusion?

Conditions for Fusion to Occur

Fusion requires extreme conditions to overcome the Coulomb repulsion between positively charged nuclei. Let’s break down the three key conditions:

High Temperature

At high temperatures (millions of kelvin), nuclei move at very high speeds.
This increases the likelihood that they will collide with enough energy to overcome the repulsive electrostatic force between them.

Example

In stars, core temperatures often exceed 10 million K, making fusion possible.

High Density

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Nuclear Fusion: The Power Behind Stars

Deuterium-Tritium Fusion

Consider the fusion of deuterium ($ ^2\text{H} $) and tritium ($ ^3\text{H} $): $$^2\text{H} + ^3\text{H} \rightarrow ^4\text{He} + ^1\text{n}$$
In this reaction, a helium nucleus ($ ^4\text{He} $) and a neutron ($ ^1\text{n} $) are produced.
The mass of the reactants is slightly greater than the mass of the products, and this mass difference ($ \Delta m $) is converted into energy: $$Q = \Delta m c^2$$
For this reaction, the energy released is approximately 17.6 MeV (million electron volts) per fusion event, an immense amount of energy at the atomic scale.

Example question

Calculate the energy released in the reaction $^2\text{H} + ^3\text{H} \rightarrow ^4\text{He} + ^1\text{n}$, given the following atomic masses:

$^2\text{H}$: 2.014102 u
$^3\text{H}$: 3.016049 u
$^4\text{He}$: 4.002602 u
$^1\text{n}$: 1.008665 u

Solution

The mass defect is: $$\Delta m = (2.014102 + 3.016049) - (4.002602 + 1.008665) = 0.018884\,\text{u}$$
Convert this mass into energy using $1\,\text{u} = 931.5\,\text{MeV}\,c^{-2}$: $$Q = \Delta m c^2 = 0.018884 \times 931.5 = 17.6\,\text{MeV}$$

Active recall

What is the role of the mass defect in determining the energy released during nuclear fusion?

Conditions for Fusion to Occur

Fusion requires extreme conditions to overcome the Coulomb repulsion between positively charged nuclei. Let’s break down the three key conditions:

High Temperature

At high temperatures (millions of kelvin), nuclei move at very high speeds.
This increases the likelihood that they will collide with enough energy to overcome the repulsive electrostatic force between them.

Example

In stars, core temperatures often exceed 10 million K, making fusion possible.

High Density

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Topic A - Space, time and motion5 subtopics

Topic B - The particulate nature of matter5 subtopics

Topic C - Wave behaviour5 subtopics

Topic D - Fields4 subtopics

Topic E - Nuclear and quantum physics5 subtopics

IB Physics E.5.1 Nuclear Fusion in Stars Notes

Topic A - Space, time and motion5 subtopics

Topic B - The particulate nature of matter5 subtopics

Topic C - Wave behaviour5 subtopics

Topic D - Fields4 subtopics

Topic E - Nuclear and quantum physics5 subtopics

Nuclear Fusion: The Power Behind Stars

Deuterium-Tritium Fusion

Conditions for Fusion to Occur

High Temperature

High Density

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Nuclear Fusion: The Power Behind Stars

Deuterium-Tritium Fusion

Conditions for Fusion to Occur

High Temperature

High Density

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

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