Biot–Savart law (magnetic field of a current element) (dB = (μ₀/4π) I dl×r̂ / r²)
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dB = (μ₀/4π) I dl×r̂ / r²
What each symbol means
| Symbol | What it stands for |
|---|---|
| I | Steady current in the conductor (A) |
| r | Distance from element to field point (m) |
| dB | Infinitesimal magnetic field at the field point (T) |
| dl | Vector length element along current direction |
| r̂ | Unit vector from element toward field point |
| μ₀ | Permeability of free space = 4π×10⁻⁷ T·m/A |
When to use this
Valid for steady currents in vacuum (or non-magnetic media with μ₀→μ). Direction from right-hand cross product Idl×r̂. Superpose by integrating all elements.