Φ Magnetic Flux

In the application of magnets, magnetic flux (Magnetic Flux) is an important index to measure the performance of magnets, especially in the fields of motors, audio speakers, etc.

The concept of magnetic flux

Assuming that in a uniform magnetic field with magnetic induction intensity B, there is a plane with area S and perpendicular to the direction of the magnetic field, the product of magnetic induction intensity B and area S is called the magnetic flux passing through this plane, referred to as magnetic flux, symbol “Φ”, The unit is Weber (Wb). Magnetic flux is a physical quantity representing the distribution of the magnetic field, and it is a scalar quantity. If there are two magnetic fluxes in opposite directions passing through a plane, then the magnetic flux on the plane is the algebraic sum of the magnetic fluxes in opposite directions. Φ=B·S, when there is an angle θ between the vertical plane of S and B, Φ=B·S·cosθ

The relationship between magnetic flux density and magnetic flux

Magnetic flux density is an alias of magnetic induction (B), which represents the number of magnetic field lines passing through a unit area perpendicularly. The magnetic flux density is referred to as the magnetic flux density. It reflects the density of the magnetic force lines in quantity. The stronger the magnetic field, the denser the magnetic force lines. The larger the value of B, the greater the magnetic flux in the case of the same area.

Φ Magnetic Flux

Measurement of magnetic flux

Fluxmeter is a kind of magnetic measuring instrument for measuring magnetic flux. There are three types of magnetoelectric, electronic and digital integral types commonly used. It is mainly calibrated and traced by mutual inductance method or volt-second method.

In recent years, domestic permanent magnet manufacturers have widely used Helmholtz coils (Helmholtz coil) to test batch products. The Helmholtz coil is a device that produces a uniform magnetic field in a small area. This coil has an open nature, which can easily put the magnet under test in or out, and can also be used for direct visual observation.

Purchasers need to pay attention to the fact that the fluxmeter is prone to errors when measuring small-sized magnets, and the reading of the fluxmeter is related to the position of the sample in the measuring coil. The calibration of the test coil needs to pass a constant current to test the magnitude of the magnetic field in a zero magnetic field environment, and then obtain the constant of the test coil. However, there are only a handful of real zero magnetic field laboratories in the world, so the calibration of test coils is difficult to promote in the industry. The lack of calibration of test coils will directly affect the accuracy and reliability of the test, which may lead to some trade disputes .

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