A square of side L meters lies in the x-y plane in a region where the magnetic field is given by $\mathrm{B}={\mathrm{B}}_0(2\hat{\mathrm{i}}+3\hat{\mathrm{j}}+4\hat{\mathrm{k}})$ Tesla, where B₀ is constant.
The magnitude of flux passing through the square is

Magnetic flux is defined as the total number of magnetic lines of force passing normally through an area placed in a magnetic field and is equal to the magnetic flux linked with that area.
Square ties in X-Y plane in $\overrightarrow{\mathrm{B}} \mathrm{so} \overrightarrow{\mathrm{A}}={\mathrm{L}}^2\hat{\mathrm{k}}$
$\begin{array}{l}\mathrm{Q}=\mathrm{B}\cdot \mathrm{A}\\ ={\mathrm{B}}_0(2\widehat{\mathrm{i}}+3\widehat{\mathrm{j}}+4\widehat{\mathrm{k}})\cdot \left({\mathrm{L}}^2\widehat{\mathrm{k}}\right)\\ ={\mathrm{B}}_0[2\times \hat{\mathrm{j}}\widehat{\mathrm{k}}+3\times \hat{\mathrm{j}}\widehat{\mathrm{k}}+4\times \widehat{\mathrm{k}}\cdot \widehat{\mathrm{k}}]\\ ={\mathrm{B}}_0{\mathrm{L}}^2[0+0+4]\\ =4{\mathrm{B}}_0{\mathrm{L}}^2\mathrm{Wb}\end{array}$