field long straight wire

Question

Magnetic field at distance r from long straight wire carrying current I?

RankGuru · Accepted Answer

1. **Biot-Savart/Ampere's Law**: For a long straight conductor, the magnetic field forms concentric circular loops around the wire.
2. **Ampere's Law Application**: $\oint \vec{B} \cdot d\vec{l} = \mu_0 I$. For a circular path of radius $r$, $B (2\pi r) = \mu_0 I$.
3. **Isolate B**: $B = \frac{\mu_0 I}{2\pi r}$.
4. **Variables**: 
   - $\mu_0$ is the permeability of free space ($4\pi 	imes 10^{-7} 	ext{ T·m/A}$).
   - $I$ is the current and $r$ is the radial distance from the wire.
5. **Direction**: Determined by the Right-Hand Thumb Rule.

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field long straight wire

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