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 $10\mathrm{A}$?

A wire near the equator carries a current perpendicular to the Earth's magnetic field of $50\mathrm{\mu }\mathrm{T}$ in a location where the field is parallel to the ground and points straight north. Assuming it was of correct magnitude, what direction should the current be in to levitate the wire?

A wire near the equator carries a current perpendicular to the Earth's magnetic field of $50\mathrm{\mu }\mathrm{T}$ in a location where the field is parallel to the ground and points straight north. The wire has a mass per length of $5.9\mathrm{g}/\mathrm{m}$. What magnitude of current in the wire could balance it against the force of gravity? (This example is not very realistic. The mass per length given would be reasonable for a very thin wire which could not handle this large of a current for very long.)