Ampère's Force Law: Force between Parallel Currents

Initializing live version
Download to Desktop

Requires a Wolfram Notebook System

Interact on desktop, mobile and cloud with the free Wolfram Player or other Wolfram Language products.

Ampère's force law for parallel currents can be regarded as an analog of Coulomb's law for charges. The force per unit length between two current elements separated by a distance is given by , where is the permeability of free space. In contrast to Coulomb's law, parallel current elements attract (signified by the minus sign) while opposing currents repel. The formal SI definition of the ampere is "the constant current which will produce an attractive force of newtons per meter of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one meter apart in a vacuum."

Contributed by: S. M. Blinder (March 2011)
Open content licensed under CC BY-NC-SA



Ampère's force law is a consequence of the Lorentz force on the moving charge in each current element acted upon by the magnetic field produced by the other current element: .


Wikipedia, "Ampère's Force Law,"ère's_force_law.

Feedback (field required)
Email (field required) Name
Occupation Organization
Note: Your message & contact information may be shared with the author of any specific Demonstration for which you give feedback.