Electrical measurements - Magnetic flux

In physics, specifically electromagnetism, the magnetic flux (often denoted Φ or Φ_B) through a surface is the component of the magnetic B field passing through that surface. The SI unit of magnetic flux is the weber (Wb) (in derived units: volt-seconds), and the CGS unit is the maxwell. Magnetic flux is usually measured with a fluxmeter, which contains measuring coils and electronics, that evaluates the change of votage in the measuring coils to calculate the magnetic flux.

  

The magnetic flux through a surface when the magnetic field is variable relies on splitting the surface into small surface elements,over which the magnetic field can be considered to be locally constant. The total flux is then a formal summation of these surface elements.