# Magnetic tension

In electrodynamics (electricity theory), the term of the magnetic tension (V_m: path integral over the magnetic field strength H) or magnetic flux (θ) is to be understood as a measure describing the excitatory force of the magnetic field strength. It corresponds to the total current flowing through an area enclosed by the magnetic field lines. In physics, the magnetic tension can be compared with the voltage (U), which in turn plays an important role in the magnetic circuit (only formal analogy).

## How does magnetic tension develop?

In current-carrying conductors, the moving charge carriers generate a magnetic field. It is also said in this context that electrons flow through a magnetic field. If several conductors are next to each other, as in a coil, for example, this flux is proportional to the sum of the number of turns. The magnetic tension that emerges from the coil is the cause of the magnetic field, much like the voltage in electricity is responsible for the current.

## How to calculate the magnetic tension?

The international unit standard for formula symbols specifies the unit amperes (A) for the magnetic voltage. With the so-called Hopkinson law (named after the British physicist John Hopkinson), there exists a formula equation which relates the magnetic tension to the magnetic resistance (R_m) and the magnetic flux (Φ):

Furthermore, the so-called Flood Law describes the dependence of the magnetic flux and the trapped current. H is the magnetic field strength:

## Magnetic voltage at line conductor and coil

With an electrical line conductor one can imagine the magnetic tension as a plane fan emerging from the ladder. For induced current, the magnetic stress can be specified as a function of the angle α between two fan surfaces:

If the magnetic field strength H is taken into account:

ds is a section of the field length l of the magnetic field strength with l = αr (r is the radius around the current I on which the field is measured).

If a coil is induced as a magnetic voltage source (traversed by current I), the ampere-turn number N is used. Even if the coil contains an iron core or other high permeability material, the magnetic strain can be determined as follows:

With the help of this approximation, it is possible to deduce the magnetic field strength and the magnetic flux density (if the permeability number is known) from the iron path length and flux.

Especially in electrical engineering the magnetic voltage is used for voltage stabilizers and electromagnets.