Permeability of free space

The permeability of free space, μ₀, is a physical constant used often in electromagnetism. It is defined to have the exact value of 4π x 10^-7 N/A² (newtons per ampere squared). It is connected to the energy stored in a magnetic field, see Hyperphysics for specific equations.

It is related to the speed of light by the equation:

$c=\frac{1}{\sqrt{{\mu }_0{ϵ}_0}}$

where

• $c$ is the speed of light and
• ${ϵ}_0$ is the permittivity of free space.

A magnetic field, $B$ in a region of space has field energy associated with it. That energy density is defined as:

Energy $=\frac{B^2}{2{\mu }_0}$

One particular use is the magnetic force. The constant gives how strong the force is between two electric currents separated by a distance:

$F=\frac{I_1{I}_2}{2\pi {\mu }_{0}r}$

where

• $F$ is the Magnetic force,
• $I_1$ and $I_2$ are two currents, and
• $r$ is the separation between the wires carrying the currents.

Visit Hyperphysics for more information on this constant.

For Further Reading

For further information please see the related pages below:

• Permittivity of free space
• Magnetic field
• Magnetic flux
• Inductance
• Or explore a random page