## Conceptual Physics (12th Edition)

In an electric field E, a charge q feels a force of magnitude $q \times E$. This can increase the speed of a charged particle. The magnetic force that acts on a charged particle is always perpendicular to the particle's motion. It guides the particles into curved paths. There is no component of the force that acts along the instantaneous direction of motion, so the magnetic field cannot speed up, or slow down, a moving charged particle.