Magnetic Flux Formula

Magnetic Flux

Magnetic flux is defined as the total number of magnetic field lines through a given coil or area. It is the common component of the magnetic field which passes through the coil. Magnetic flux is denoted by ΦB where B is a magnetic field and its unit is Weber (Wb). The magnetic flux value depends on the magnetic field direction and it is a vector quantity.

The magnetic flux formula is given by,

\(\begin{array}{l}\Phi_B=B\cdot A\end{array} \)
\(\begin{array}{l}\Phi_B = BA\ cos\ \theta\end{array} \)


B = Magnetic field,

A =  Surface area and

θ =  Angle between the magnetic field and normal to the surface.

Solved Example

Example 1

The Dimension of a rectangular loop is 0.50m and 0.60m. B and θ are 0.02T and 45° respectively. Determine the magnetic flux through the surface.



Dimensions of rectangular loop = 0.50m and 0.60m,

B = 0.02T

θ = 45°

Magnetic flux formula is given by

ΦB = B A Cos θ

Area, A = 0.50 × 0.60

            = 0.3 m2

ΦB = 0.02 × 0.3 × Cos 45

ΦB = 0.00312 Wb

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