Call Girl in Bur Dubai O5286O4116 Indian Call Girls in Bur Dubai By VIP Bur D...
Phy b9 2-2
1. Solenoid1.长直螺线管内的磁感应强度
CAI
We assume that the length of the solenoid
is much greater than the diameter
Magnetic field lines for a real solenoid of finite length. The field
is strong and uniform at interior points such as P1 but relatively
weak at external points such as P2.
退出返回
2. ∫∫ ∫∫ ∫ ⋅+⋅+⋅+⋅=⋅
a
d
c
b
d
cL
b
a
ldBldBldBldBldB
vvvvvvvvvv
0=⋅=⋅ ∫∫
a
d
c
b
ldBldB
vvvv
CAI
∫ =⋅
d
c
ldB 0
vv
退出返回
4. 2. 无限大平面电流的磁场
An infinite slab carries a uniform current
α
Surface current density
l
I
∆
∆
α =
1011 lBlBl αµ=+ 2
0
αµ
=B
l∆
I∆α
10 lαµ=
面电流密度
a b
cd
1l
2l
B
r
B
r
∫∫∫ ⋅+⋅=⋅
c
b
b
aL
ldBldBldB
rrrrrr
∫∫ ⋅+⋅+
a
d
d
c
ldBldB
rrrr
∫∫ ⋅+⋅=
d
c
b
a
ldBldB
rrrr
返回 退出
Bd ′
r
Bd
r 2Bd
r
1Bd
r
5. The magnetic field produced by a moving charged particle
nvq
r
qnvSI =
ld//vq
rr
3
0
4 r
rlId
Bd
rr
r ×
=
π
µ
载流子
SdlvqnlId
rr
=
ofcarriereschargebyproducedisThe nSdldNBd =
r
lqnvSdlId
rr
=
3
0
4 r
rvqnSdl
rr
×
=
π
µ
3
0
4 r
rvq
dN
Bd
B
rrr
r ×
==
π
µ
A charge carrier
cv <<
退出返回
7. §9.4 带电粒子在磁场中的运动
The Motion of a Charged Particle in a Magnetic Field
(1) A charged particle moves parallel to
a constant magnetic field
BvqF
rrr
×=
+q
B
r
v
r
θsinqvBF =
0=θ
0=F
退出返回
8. (2) A charged particle moves perpendicularly to a
constant magnetic field
+
q
B
r
v
r
F
r
RR
×× ×× ×× ×× ×× ×× ××
×× ×× ×× ×× ×× ×× ××
×× ×× ×× ×× ×× ×× ××
×× ×× ×× ×× ×× ×× ××
×× ×× ×× ×× ×× ×× ××
×× ×× ×× ×× ×× ×× ××
++
B
r
v
r
F
r
BvqF
rrr
×= qvB=θsinBqvF =
R
v
mqvB
2
=
qB
mv
R =
退出返回
9. qB
mv
R =
qB
m
v
R
T
ππ 22
==
周期
m
qThe period
m
qB
T
f
π2
1
==频率 荷质比
The frequency charge-to-mass ratio
The period and frequency are independent of the speed.
All particles with the same charge-to-mass ratio take the
same time T (the period) to complete one round trip.
退出返回
10. (3)Initial velocity is not perpendicular to magnetic field
The particle will move in a helical path about the
direction of the field vector 螺旋运动
h
⊥v
//v
++
θ
B
r
v
rθcosvv// =
θsinvv =⊥
pitch of the helix 螺距
匀速圆周运动
匀速直线运动
the distance between adjacent turns
The velocity vector of such a particle resolved into two
components, one parallel to and one perpendicular to
it.
v
r
B
r
⊥v//v CAI
返回 退出
11. h
⊥v
//v
++
θ
B
r
v
r
move in a helical
path
螺旋运动
pitch of the helix 螺距
qB
m
T
π2
=
θ
π
cos
2
v
qB
m
Tvh // ==
The parallel component determines the pitch h of the helix
退出返回
12. Magnetic focusing 磁聚焦 从磁场某点发射出一束带电粒子流
⊥v
//v
v
r
B
rθ
++
v
qB
m
v
qB
m
h
π
θ
π 2
cos
2
==
vvv ≈= θcos//
θθ vvv ≈=⊥ sin
2
RS π= CAIqfI =
Magnetic mirror 磁镜
m
qB
f
π2
=
qB
mv
R ⊥
=2
qfRISM π==
B
mv
M
2
2
1
⊥
=
const.=M
222
2
1
2
1
2
1
//mvmvmv += ⊥
退出返回
13. A charged particle spiraling in a nonuniform magnetic field.
(The particle can become trapped, spiraling back and forth
between the strong field regions at either end.) Note that the
magnetic force vectors at the left and right sides have a
component pointing toward the center of the figure.
退出返回
18. The auroral oval surrounding Earth's geomagnetic north pole.
Magnetic field lines converge toward that pole. Electrons moving
toward Earth are “caught by” and spiral around these field lines,
entering the terrestrial atmosphere at high latitudes and producing
aurora within the oval.
退出返回
