Chapter 21 potential 第八章静电场 1)Work done by electrostatic Force 点电荷的电场 Electric field of a point charge dW=anE·da B ggo 4兀F,d7 B F·dl= rdl cos e=rdr q40 0 4π60Chapter 21 potential 第八章静电场 q 1) Work done by Electrostatic Force 0 q r  W q E l   d d 0   r l r qq   d 4π 3 0 0    r  dl  rdl cos    rdr r r qq W d 4π d 2 0 0   点电荷的电场 Electric field of a point charge l d dr Ar A Br B  E 