What is the formula of magnetic field B?
Andrew Rivera
Published Jan 14, 2026
B = μ0I/(2πr). This equation is derived from one of Maxwell's equations called Ampere's law. The proportional constant μ0 = 4π*10-7 N/A2 is called the permeability of free space . If we imagine a circular loop of radius r, then the magnetic field is tangential to the loop.
permeability of free space
The permeability constant μ0, also known as the magnetic constant or the permeability of free space, is the proportionality between magnetic induction and magnetizing force when forming a magnetic field in a classical vacuum.
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