复旦大学物理学系 2006~2007学年第二学期期末考试试卷参考答案 A卷 课程名称:大学物理(下)课程代码:PHYS12000.05 开课院系:物理学系考试形式:闭卷 1 There are six interaction terms, one for every charge pair, number the charges clockwise from the upper left hand corner, then u2=9/rega u23=9" /4Eoa 34=92/4mE0a 2/4re0 43=q2/4xe0(2a) l24=q ld these terms and get u (4+√2) the amount of work required Is w=u 2 There are four current segments that could contribute to the magnetic field. the straight segments, however, contribute nothing because the straight segments carry currents either directly toward or directly away from the point p that leaves the two rounded segments. Each contribution to B can be found by idsxr rde The contribution to b from the top arc is: 4018 The direction is into the page