# Nuclear Fusion Physics and Technology/Example page

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## Contents

#### Note: Electromagnetic field[edit]

As summarized in previous chapters, electromagnetic field is mathematical abstraction of two projections and , which meets Maxwell equations

and may be represented by field lines defined as

#### Definition: Open field line[edit]

Field line is *open*, when it is not closed in plasma.

#### Definition: Closed field line[edit]

Field line is *closed*, when it is closed in plasma.

#### Theorem: Magnetic field line equation[edit]

Lets assume electromagnetic field with field lines. Then

__Proof:__

The theorem results from field line definition directly

which is a vector equation of three scalar equations

and thus may be written