A moving charged particle produces a magnetic field due to its electric charge and its motion. This phenomenon is described by a fundamental principle in electromagnetism known as Ampere's law.
According to Ampere's law, the magnetic field around a current-carrying conductor or a moving charged particle is proportional to the current or the velocity of the charged particle, respectively. When a charged particle moves, it creates a current. This current, referred to as "convection current," arises from the motion of charged particles within the material or the motion of the charged particle itself.
The convection current produces a magnetic field that circulates around the path of the moving charged particle. The magnetic field lines form closed loops, with their direction determined by the right-hand rule. Specifically, if you point your thumb in the direction of the current or the velocity of the charged particle, the curled fingers indicate the direction of the magnetic field lines.
The strength of the magnetic field produced by a moving charged particle depends on several factors, including the charge of the particle, its velocity, and the distance from the particle. As the velocity of the charged particle increases, the magnitude of the magnetic field it produces also increases.
This phenomenon is fundamental to electromagnetism and has wide-ranging applications. It explains phenomena such as the magnetic fields around moving charges, electric currents in wires, and the behavior of charged particles in magnetic fields. Additionally, it forms the basis for various technologies like electric motors, generators, and particle accelerators.