2 Displacement Current位移电流 As an example of this sort of induction, we consider the charging of a parallelplate capacitor (平行板电容器) with circular plates(very large)as shown in the following figure. Electric field Magnetic field Varving!!
Magnetic field 2. Displacement Current 位移电流 I R As an example of this sort of induction, we consider the charging of a parallelplate capacitor （平行板电容器） with circular plates(very large) as shown in the following figure. Varying!! Electric field
For the loop l: 乐HF·a= To the surface si, we have I·d=l To the surface S,, we have( Contradiction(矛盾) I·d=0 Ampere' s law is invalid(无效 的) for the varying electromagnetic field
H dl ? L = For the loop L: To the surface S1 , we have H dl I L = L S1 S2 I To the surface S2 , we have = 0 L H dl Contradiction (矛盾） Ampere’s law is invalid(无效 的 )for the varying electromagnetic field
Introducing the displacement current Id d d D t ∫D.ds=∫ ds dt dt s at D
S Introducing the displacement current Id : = = = S D d dS t D D S dt d t Φ I S d d d D
Ampere's law is modified(修改)as H d=u+ OpD t Displacement current d L S
L S1 S2 I Displacement current Id t Φ H dl I D L = + 传 Ampere’s law is modified(修改） as