# Encyclopedia Magnetica

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calculator:magnetic_field_of_straight_conductor

## Calculator of magnetic field of straight round conductor

 $$H(d) = \frac{I_{tot}·r^2}{2·π·d·R^2}$$ (A/m) Equations are valid inside as well as outside of the wire (with certain assumptions) $$B(d) = \frac{μ_r·μ_0·I_{tot}·r^2}{2·π·d·R^2}$$ (T) Total current in wire Itot (A) = (A) (mA) Radius of wire R (mm) = (m) (mm) Radius from centre d (mm) = (km) (m) (mm) Relative permeability of wire μr (unitless) = Relative permeability of surrounding medium μr (unitless) =         H = (A/m)     B = (T) (mT) (μT) Assumptions: current distribution is uniform, permeability is uniform and isotropic, high-frequency effects (radiation and relativistic) are negligibly small, where: $I_{tot}$ - total current (A) in the wire, $r$ - variable radius (m) within the wire from its centre such that $0 \leq r \leq R$ (and $r=d$ within the wire) , $d$ - any positive variable radius (m) from centre of wire, $R$ - outer radius (m) of the wire, $μ_r$ - relative permeability (unitless) of wire or the surrounding medium, and $μ_0$ = 4·π·10-7 H/m is the permeability of vacuum. 