The magnetic flux of a uniform field B over a flat surface with area A and normal vector n is:
![\Phi=AB\cos\theta](https://img.qammunity.org/2023/formulas/physics/college/q5h2uy7brxchy665s7ail861l1nexkmqhd.png)
Where θ is the angle between the normal vector n and the direction of B.
If the normal to the plane of the loop is perpendicular to the field, then θ=90º:
![\Phi=AB\cos(90º)=AB\cdot0=0](https://img.qammunity.org/2023/formulas/physics/college/9g6nsmx3a271ks8wh0sau72c7mhzk6jesf.png)
Therefore, the magnetic flux is 0.