ビオ・サバールの法則
The Biot–Savart law is used for computing the resultant magnetic field B at position r in 3D-space generated by a flexible current "I" (for example due to a wire). A steady (or stationary) current is a continual flow of charges which does not change with time and the charge neither accumulates nor depletes at any point. The law is a physical example of a line integral, being evaluated over the path "C" in which the electric currents flow (e.g. the wire). The equation in SI units is