Name: magnetic flux through surfaces
Uploaded: 2026-07-09T14:36:53.339Z
Duration: 1 min 19 s
Channel: JoVE

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North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

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Motion and Stability- Forces and Interactions

PS.PSc.6.4

Magnetic Flux

The magnetic flux measures the strength of a magnetic field penetrating through a given surface area.
Consider a surface with several tiny elements of area dA placed in a magnetic field B.
The magnetic flux through this element is the dot product of the magnetic field and the area vector.
The magnetic flux through the entire surface is its integral over the whole surface. If the magnetic field is uniform throughout the surface, then the net magnetic flux is B A cos &#x3B8;, where &#x3B8;&#xA0;is the angle between the magnetic field and the area.
When the magnetic field is perpendicular to the surface, the magnetic flux is maximum. When it is parallel to the surface, the flux is zero.
Its SI unit is weber.
The field lines in a magnet do not begin or end at any point. Hence, the number of lines entering and leaving a closed surface are equal; therefore, the total magnetic flux through a closed surface is zero. This equation is known as Gauss&#x2019; law for magnetism.

<ol>
	<li>Young, H.D e Freedman, R.A. (2012). Fisica universitaria con fisica moderna. San Francisco, CA: Pearson; sezione 27.3; pagine 890-892.</li>
</ol>

flusso magnetico

Il flusso magnetico misura il numero di linee di campo magnetico che attraversano una data area superficiale. L&#x27;unit&#xE0; SI per il flusso magnetico &#xE8; il weber (Wb). Il flusso magnetico &#xE8; una quantit&#xE0; scalare. Dipende da tre fattori: la intensit&#xE0; del campo magnetico B, l&#x27;area attraverso cui passano le linee di campo e l&#x27;orientamento relativo del campo con l&#x27;area superficiale.

Supponiamo che una superficie sia divisa in elementi di area dA. Per ciascun elemento, viene determinata la componente del campo magnetico che &#xE8; perpendicolare alla superficie nella posizione di quell&#x27;elemento. Questa componente varia generalmente da punto a punto sulla superficie. Il flusso magnetico attraverso questo elemento &#xE8; definito come il prodotto scalare del vettore del campo magnetico e del vettore dell&#x27;elemento di area. Il flusso magnetico totale attraverso qualsiasi superficie, aperta o chiusa, &#xE8; la somma delle contribuzioni al flusso da tutti gli elementi individuali.

Se il campo magnetico &#xE8; perpendicolare alla superficie ed &#xE8; uniforme in tutta essa, allora il flusso magnetico ha il valore massimo di BA. Quando il campo &#xE8; parallelo alla superficie, il flusso magnetico ha un valore minimo di zero.

Secondo la legge di Gauss, il flusso elettrico totale che passa attraverso una superficie chiusa &#xE8; proporzionale alla carica elettrica totale all&#x27;interno della superficie. Il flusso elettrico totale &#xE8; zero quando un dipolo elettrico &#xE8; racchiuso da una superficie chiusa poich&#xE9; non c&#x27;&#xE8; alcuna carica complessiva. Per analogia, il flusso magnetico totale attraverso una superficie chiusa sarebbe proporzionale alla carica magnetica totale racchiusa se ci fosse una singola carica magnetica o un monopolio magnetico. Tuttavia, nonostante ricerche approfondite, non &#xE8; mai stato visto alcun monopolio magnetico. Pertanto, il flusso magnetico totale attraverso una superficie chiusa &#xE8; sempre zero.

Poich&#xE9; le linee di campo magnetico formano sempre circuiti chiusi o originano dai poli nord e sud dello stesso magnete, il numero totale di linee di campo che entrano in una superficie chiusa &#xE8; sempre uguale al numero totale di linee di campo che escono dalla superficie. Pertanto, il flusso netto attraverso la superficie &#xE8; zero. Questa osservazione &#xE8; chiamata legge di Gauss del magnetismo.

Flusso magnetico

The magnetic flux measures the number of magnetic field lines passing through a given surface area. The SI unit for magnetic flux is the weber (Wb). ...

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Physics

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Unit 1

Unità 1

Magnetic Forces and Fields

Forze e Campi Magnetici

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

magnetic flux through surfaces

Magnetic flux through a surface describes how much magnetic field passes across that surface. It is measured in weber (Wb), the SI unit for magnetic flux. Magnetic flux is a scalar quantity, not a vector.

Three factors shape magnetic flux. They are the magnetic field strength B, the area the field crosses, and the orientation of the field relative to the surface. For a small area element dA, the flux depends on the part of the magnetic field that is normal, or perpendicular, to that element at that point. That normal component can change from place to place across the surface.

The flux through each small element is written as a dot product between the magnetic field vector and the area element vector. The total magnetic flux through a surface, whether it is open or closed, is found by adding the flux from all the small elements. If the magnetic field is uniform and perpendicular to the surface, the flux reaches its maximum value, BA. If the field is parallel to the surface, the flux is zero.

Magnetic flux also connects to Gauss's law. For electric fields, the total electric flux through a closed surface is proportional to the electric charge inside it. A closed surface around an electric dipole has zero total electric flux because there is no net charge. By analogy, a closed surface would have magnetic flux proportional to enclosed magnetic charge if magnetic monopoles existed.

No magnetic monopole has ever been observed, even after many searches. Because of that, the total magnetic flux through any closed surface is always zero. Magnetic field lines form closed loops, or they leave one pole of a magnet and return to the other. So the number of field lines entering a closed surface equals the number leaving it. This result is called Gauss's law of magnetism.

Magnetic Flux Through Surfaces

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Magnetic flux through a surface describes how much magnetic field passes across that surface. It is measured in weber (Wb), the SI unit for magnetic flux. Magnetic flux is a scalar quantity, not a vector. Three factors shape magnetic flux. They are the magnetic field strength B, the area the field crosses, and the orientation of the field relative to the surface. For a small area element dA, the flux depends on the part of the magnetic field that is normal, or perpendicular, to that element at...

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Explore magnetic flux through surfaces, the weber unit, how field strength and orientation affect flux, and why closed surfaces have zero net magnetic flux.

Magnetic Flux Through Surfaces | JoVE K12

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Magnetic Flux Through Surfaces

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