Units and Constants

We have a new constant, $\mu_0$, the so-called permeability of free space. It functions as a coupling constant in the strength of magnetic interactions (just like $\epsilon_0$ for electrostatic and $G$ for gravitational). It's value is conveniently expressed as

$$\mu_0={4\pi \times 10^{-7} \textrm{T} \cdot \textrm{m/A}}.$$

We also have one new unit, the tesla $T$, where

$$[T]=1 \textrm{N}\cdot \textrm{A/m}.$$