Final answer:
A magnetic field is created around a wire when an electric current passes through it, and this effect is described by Ampère's law and the right-hand rule.
Step-by-step explanation:
A magnetic field is produced around a wire through which a current flows. This phenomenon occurs due to the charge distribution on the wire. As the electric current varies, so do the electric field (E) and charge distribution, creating a magnetic field that propagates outward at the speed of light.
The strength and direction of the magnetic field produced can be analyzed using Ampère's law and the right-hand rule. For a long straight wire, the magnetic field lines form concentric circles around the wire, with the direction determined by pointing the thumb of the right hand in the direction of current flow; the curled fingers then show the direction of the magnetic field. This relationship is critical in the functioning of electrical devices such as transformers and solenoids, where controlled magnetic fields are essential.