29. Sources of Magnetic Field

At what distance from a wire carrying a $10\mathrm{A}$ current is the magnetic field strength equal to $50\mathrm{\mu }\mathrm{T}$? This is the approximate value of the Earth's magnetic field.

Typical household wiring in the United States is 14-gauge copper wire which has a radius of $813\mathrm{\mu }\mathrm{m}$. What is the magnetic field strength inside the wire, halfway between the center and the outside edge, when it is carrying a typical household current of $10\mathrm{A}$?