Electricity & Magnetism

Energy Density (Magnetic Field)

u = \frac{B ^{2}}{2 μ _{0}}

Energy stored per unit volume in a magnetic field.

Variables

u

Energy density

Energy per unit volume

J/m³

B

Magnetic field

Field strength

T

μ₀

Permeability

4π×10⁻⁷

H/m

Derivation

From U = ½LI² and B = μ₀nI, u = B²/(2μ₀).

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