🔌 Magnetic Field of a Straight Wire Calculator

Magnetic Field Around a Straight Wire

An infinitely long, straight wire carrying current I produces a circular magnetic field around it, with magnitude given by Ampère’s Law as B = μ₀I / (2πr), where μ₀ is the permeability of free space (4π×10^-7 T·m/A) and r is the distance from the wire.

The field strength falls off inversely with distance — doubling your distance from the wire halves the field strength. This fundamental relationship underlies the design of solenoids, transformers, and any application involving current-carrying conductors and their surrounding magnetic fields.