2. Ampère Circuital Theorem§9.3 安培环路定理
Andre Marie Ampère
(1775-1836)
∫ =⋅
L
ldE 0
rr
Electrostatic field
∫ =⋅
L
?ldB
rr
Magnetic field
r
I
B
π
µ
2
0
=
L
l
r
∫ ⋅
L
ldB
rr
∫ ⋅=
L
dlB ∫=
L
dlB
Ir
r
I
0
0
2
2
µπ
π
µ
==
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3. 0=⋅∫cd
ldB
rr
∫ =⋅
ab
ldB 0
rr
b
∫∫ ⋅+⋅=
21 CC
ldBldB
rrrr
∫ ′
⋅
C
ldB
rr
∫∫ ⋅+⋅−=
21 CC
dlBdlB
)2()2( 2211 rBrB ππ +−=
)2(
2
)2(
2
2
2
0
1
1
0
r
r
I
r
r
I
π
π
µ
π
π
µ
+−=
0
r
I
B
π
µ
2
0
=
=
∫ ∑=⋅
L
i
iIldB 0µ
rr
Ampère Circuital Theorem
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4. ∫ ∑=⋅
L
i
iIldB 0µ
rr
The integral is taken around that closed path L
Ampère Circuital Theorem
L 在磁场中任取的一闭合线，规定一个绕行方向
l
r
d infinitesimal lengthL上的任一线元
The total current enclosed by any closed path L∑i
iI
Curl your right hand around the loop L, with the fingers pointing
in the direction of integration. A current through the loop in the
general direction of your outstretched thumb is assigned a plus
sign, and a current generally in the opposite direction is assigned
a minus sign.
电流的符号规定：
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