• # question_answer                 A charged particle moves through a magnetic field in a direction perpendicular to it. Then the:   A)                                                                                                                                                                            acceleration remains unchanged                              B)                 velocity remains unchanged C)                 speed of the particle remains unchanged             D)                 direction of the particle remains unchanged

When a charged particle moves through a perpendicular magnetic field, then a magnetic force acts on it which changes the direction of particle but does not alter the magnitude of its velocity (i.e. speed).                                 Note:    If a charged particle moves at ${{45}^{o}}$ to magnetic field then path of the particle will be a helix whose circular part has radius according to relation $r=\frac{mv\,\sin \theta }{qB}$.