The electric field of the electric dipole Along the line E EA E 4πe.(r-1/2月 9L9 r -q B.=4rt+2 9 2rl E=E,+E= 4m.r0-PY4r2月 r>>1 2ql 2P .12/4r2≈0 EA 4π8。T 4πE。rThe electric field of the electric dipole -q l q r A r o   2 4 r l 2 q E o      Along the line   2 4 r l 2 q E o         2 2 2 4 1 4 2 1 4 r l r q rl E E E o A         4 0 2 2    l r  r l 3 3 4 2 4 2 r p r ql E o o A       E- E+