A magnetic field is generated around a straight conductor, like a copper rod, when an electric current passes through it. Ampere’s Circuital Law quantifies this relationship: \[ \oint B \cdot dl = \mu_0 I, \] where \( B \) represents the magnetic field, \( \mu_0 \) is the permeability of free space, and \( I \) is the current in the conductor. The magnetic field lines are concentric circles surrounding the conductor. The direction of the field is determined by the right-hand rule: align your thumb with the current's direction; the direction your fingers curl indicates the magnetic field's direction.