Main concepts

Biot-Savart-Laplace law:

,

where – a vector of magnetic intensity of a field, which is created of the element of a current I ; – a radius-vector from the element I to the target point.

The modulus of magnetic field intensity:

a) the endless straight wire with a current I at a distance of r from the wire

;

b) the segment of straight wire with a current I at a distance of r _^ from the axis of a segment

,

where a₁ and a₂ – angles, which are created radius-vectors, traced from the ends of a conductor to the target point at which field is being calculated;

c) at the centre of the current-carrying coil of the radius R with a current I

;

D) at the axis of the current-carrying coil

,

where а – is the distance from the centre of coil to the target point at the axis;