# Proof involving Ampere's Law

## Homework Statement

Ampere's Law states $$\int _C \vec{B} \cdot \vec{dr} = \mu_0 \ I$$ .

By taking C to be a circle with radius r, show that the magnitude B = |B| of the magnetic field at a distance r from the center of the wire is $$B = \frac{\mu_0}{2 \pi} \ \frac{I}{r}$$

## The Attempt at a Solution

I really don't know where to start. I don't know what the components of B are, so I don't know how I'm supposed to compute this integral.

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