Magnetic Flux and Flux Linkage

Magnetic flux is a measure of the total magnetic field passing through a given area. While magnetic flux density (B) tells you how strong the field is at a point, magnetic flux (Φ) tells you the total amount of field threading through a surface. This distinction is crucial for understanding electromagnetic induction, which relies on changes in flux.

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Magnetic Flux

Magnetic flux (Φ, the Greek letter phi) through a surface of area A in a uniform magnetic field B is:

Φ = BA cosθ

where:

• Φ is the magnetic flux (Wb — weber)
• B is the magnetic flux density (T)
• A is the area of the surface (m²)
• θ is the angle between the magnetic field direction and the normal (perpendicular) to the surface

Understanding the Angle θ

The angle θ is measured between the field lines and the normal to the surface — not between the field and the surface itself.