Final answer:
A charged particle moving through a magnetic field is forced to undergo circular or spiral motion due to the perpendicular magnetic force, which acts as the centripetal force and alters the particle's path without changing its speed.
Step-by-step explanation:
A magnetic field exerts a force on a charged particle moving through it, causing the particle to experience a change in the direction of motion but not in speed. When a charged particle moves perpendicular to a uniform magnetic field, this force acts as the centripetal force that keeps the particle in uniform circular motion. The path followed by the charged particle is a circle or spiral, depending on the angle at which it enters the magnetic field and other factors such as the presence of electric fields or collisions with other particles. The exact nature of this motion is depicted in bubble chamber photographs where charged particles exhibit curved trajectories due to the magnetic forces acting upon them.
The effect of a magnetic field on a charged particle in a plasma, such as an electron or a proton, demonstrates fundamental principles of electromagnetism and is crucial for devices like mass spectrometers and the operation of particle accelerators.