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Long Straight Wire Magnetic Field & Distance

Estimate magnetic field magnitude around a long straight current-carrying wire or solve current and distance.

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A 10 A current at a perpendicular distance of 1 m gives approximately 2 µT.

B = 2 × 10⁻⁷ I / r

Enter these known values and leave the other values blank.

Assumes a thin, effectively infinite straight wire in vacuum or air, far from its ends and other conductors.
The captured coefficient uses the conventional approximation μ₀ ≈ 4π × 10⁻⁷ H/m. It is not an exact post-2019 SI constant.
Current and field are nonnegative magnitudes; distance must be positive. Direction follows the right-hand rule. Zero current gives zero field but does not determine distance.

Assumes a thin, effectively infinite straight wire in vacuum or air, far from its ends and other conductors.

Bookify treats current and magnetic field as nonnegative magnitudes and accepts zero-current fields.