Magnetic Field of a Wire

Long Straight Wire

A current-carrying wire creates a magnetic field that wraps around it in concentric circles. The field strength at distance r from an infinite straight wire:

B = rac{mu_0 I}{2pi r}

• B — magnetic field (tesla, T)
• $mu_0 = 4pi imes 10^{-7}$ T·m/A — permeability of free space
• I — current (amperes)
• r — perpendicular distance from wire (m)

The Direction

Use the right-hand rule: point your thumb in the direction of current flow; your fingers curl in the direction of the magnetic field.

Simplification

Since $mu_0 / (2pi) = 2 imes 10^{-7}$ T·m/A exactly, the formula simplifies to:

B = rac{2 imes 10^{-7} cdot I}{r}

Examples

Your Task

Implement wire_magnetic_field(I, r) returning B in tesla ($mu_0 = 4pi imes 10^{-7}$).