if the magnetic field is 2.1 m from a current carrying wire is 7.1x10^-5 T, what is the current flowing through the wire?

Question

anonymous · Answer

If we assume the wire to be infinitesimal, we have, by Ampère's law, that:
$$
\int_\gamma B\cdot dl=|B|2\pi r=\mu_0I
$$Then:
$$
|B|=\frac{\mu_0 I}{2\pi r}
$$Solve for $I$, the current in the enclosed wire.

anonymous · Answer

thanks! Does mu have a certain value?

anonymous · Answer

Indeed. $\mu_0$ is the magnetic permeability of free space, which is, by definition:
$$
\mu_0 = 4\pi \cdot 10^{-7} H/m
$$

anonymous · Answer

And, sure thing.

anonymous · Answer

thanks a lot!