Formula of magnetic field strength?

B=u0I/(2paiR), u0 is the permeability of vacuum, r is the distance from the point to the conductor, and I is the current.

The direction is judged as follows: let the current point to yourself and the magnetic field is counterclockwise.

In the international system of units, the proportional coefficient k = μ 0/4π = 10-7T m/a, where μ 0 = 4 π *10-7 t m/a.

It is called vacuum transmittance, and b = μ 0i/(2π r) = 2 *10-7i/r;

The above formula shows that the magnetic induction intensity b around an infinite current-carrying straight wire is inversely proportional to the distance of the wire to the field and directly proportional to the current.

Extended data:

It has the effect of magnetic field force on the moving probe charge, current-carrying conductor or permanent magnet introduced into the field, so the magnetic field can be described by the effect of magnetic field on the moving probe charge, and the magnetic induction intensity B is introduced as the basic physical quantity to quantitatively describe the characteristics of each point in the magnetic field, which is equivalent to the electric field intensity E in the electric field.

The reason why this physical quantity is called magnetic induction intensity instead of magnetic field intensity is because the word magnetic field intensity has been used to represent another physical quantity in history. The magnetic induction intensity reflects the interaction and stress relationship between two reference points A and B, while the magnetic field intensity is the unilateral quantity of the subject, which is constant whether Party B participates or not.

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