河南省漯河市高级中学2016-2017学年高二下学期期末考试物理试题（扫描版,答案不全）

17、解析　(1)正离子在平行金属板间匀速运动，根据平衡条件有Eq＝B0qv0                ① 根据平行金属板间的场强和电势差的关系有 E＝                                                                                                                 ② 由①②式解得 v0＝                                                                                                                    ③ (2)在磁场中，由几何关系有 L＝R＋Rtan α                                                                                                              ④ 洛伦兹力充当向心力，根据牛顿第二定律有 Bqv0＝m                                                                                                             ⑤ 由③④⑤式解得 B＝                                                                                                          ⑥ (3)在电场中正离子做类平抛运动，则有 沿y轴负方向：Rtan α＝v0t                                                                                        ⑦ 沿x轴正方向：x0＝at2                                                                                            ⑧ 离子在电场中运动的加速度a＝