Ampere's law

noun

: either of two laws in electromagnetism: (1) : the magnetic field resulting from an electric current in a circuit element is at any point perpendicular to the plane passing through the circuit element and the point, appears clockwise to an observer looking along the element in the direction of the current flow, is directly proportional to the product of the current multiplied by the length of the component of the element perpendicular to the line joining it to the point, and is inversely proportional to the square of the length of this line; or (2) : the work done in carrying a magnetic pole around any closed path is proportional to the electric current flowing through the area bounded by the closed path