电磁学（PPT讲稿）Electromagnetism revision

Electric forces on dipoles X E p F The dipole-field system has a potential energy Pole p·E

E  p  F+  F−  The dipole-field system has a potential energy: U p E   = −  dipole Electric forces on dipoles

Electric field of distributed charges △E △E △

Electric field of distributed charges y x Q r  y E   Q r  y E  

Uniformly charged rod Uniformly charged ring O(1 4兀En(z E 12(/L) 46

       2 0 axis 1 4 z Q E   ( ) r Q L E 2 4 1   0  Uniformly charged rod Uniformly charged ring

Electric field of a uniformly charged plate R △E The field almost ery large plate(R>>Z): E doesn't change with distance, near the 2 pl

R r z E   Electric field of a uniformly charged plate Very large plate (R >> z): r ( ) 0 2 Q A E  The field almost doesn’t change with distance, near the plate. Q

E| ectric potentia|(电势) Chapter 18

Chapter 18 Electric potential (电势)