Question

For a long, straight, current-carrying conductor, use Ampere’s law to find the magnitude

and direction of its magnetic field. Assume it’s radius is negligible.

Answer 1

The magnetic field strength (magnitude) produced by a long straight current-carrying wire is given by formula

$B=\frac {µ_0 I}{2πr} (1)$

where I is the current, r is the shortest distance to the wire, and the constant µ₀ is the permeability of free space.

Since the wire is very long, the magnitude of the field depends only on distance from the wire, not on position along the wire.