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 θ, where θ 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’ law for magnetism.