#!/usr/bin/env python
# coding: utf-8

# # Field Due to an Infinite Straight Current Filament

# *This simple formula can be derived directly from [Maxwell's fourth equation](../basics/maxwell.html), or Ampere's Law.*

# ![Infinite straight wire](straightwire.png)

# $B = \frac {\mu_o i}{2\pi r}$
# 
# **B** is the magnetic field, in teslas. The direction of the field is tangent to a circle on a radius **r** (in meters) from the wire.
# 
# $\mathbf \mu_o$ is the permeability constant (1.26x10<sup>-6</sup> Hm<sup>-1</sup>)
# 
# **i** is the current in the wire, in amperes.

# ---
# 
# [Magnet Formulas](../index.html), © 2018 by Eric Dennison. Source code and License on [Github](https://github.com/tiggerntatie/emagnet-py)