8/7/2019 DAO NG V SNG IN T (L thuyt v bi tp trc nghim)
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Ly thuyt - Trc Nghim Vt L
CHNG IV: DAO NG V SNG IN T1. Dao ng in t
* in tch tc thi q = q0cos( t + )
* Hiu in th (in p) tc thi 0 0os( ) os( )qq
u c t U c t C C
= = + = +
* Dng in tc thi i = q = - q0sin( t + ) = I0cos( t + +2
)
* Cm ng t: 0 os( )2 B B c t
= + +
Trong :1
LC= l tn s gc ring
2T LC= l chu k ring
1
2f
LC= l tn s ring
00 0q
I qLC
= =
0 00 0 0
q I LU LI I
C C C
= = = =
* Nng lng in trng:2
2
1 1W
2 2 2
qCu qu
C= = =
2
20
W os ( )
2
qc t
C = +
* Nng lng t trng:2
2 201
W sin ( )2 2t
q Li t
C = = +
* Nng lng in t: W=W Wt
+
2
2 20
0 0 0 0
1 1 1W
2 2 2 2
qCU q U LI
C= = = =
Ch : + Mch dao ng c tn s gc , tn s f v chu k T th W v Wt bin
thin vi tn sgc
2 , tn s 2f v chu k T/2+ Mch dao ng c in tr thun R 0 th dao ng s
tt dn. duy tr dao ng cn
cung
cp cho mch mt nng lng c cng sut:2 2 2 2
2 0 0
2 2
C U U RC I R R
L
= = =P
+ Khi t phng in th q v u gim v ngc li+ Quy c: q > 0 ng vi bn
t ta xt tch in dng th i > 0 ng vi dng in chyn bn
t m ta xt.
2. S tng t gia dao ng in v dao ng c
i lng c i lng in Dao ng c Dao ng inx q x + 2x = 0 q + 2q = 0
v ik
m
=1
LC=
m L x = Acos( t + ) q = q0cos( t + )
k1
Cv = x = - Asin( t + ) i = q = - q0sin( t + )
Chng: Dao ng v sng in t Trang 1
8/7/2019 DAO NG V SNG IN T (L thuyt v bi tp trc nghim)
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Ly thuyt - Trc Nghim Vt L
F u 2 2 2( )v
A x
= +2 2 2
0 ( )i
q q
= +
R W=W + Wt W=W + Wt
W Wt (WC) W =1
2mv2 Wt =
1
2Li2
Wt W (WL) Wt =1
2kx2 W =
2
2
q
C
3. Sng in tVn tc lan truyn trong khng gian v = c = 3.108m/sMy
pht hoc my thu sng in t s dng mch dao ng LC th tn s sng in t pht
hoc
thuc bng tn s ring ca mch.
Bc sng ca sng in t 2v
v LCf
= =
Lu : Mch dao ng c L bin i t LMinLMax v C bin i t CMinCMax th bc
sng ca
sng in t pht (hoc thu) Min tng ng vi LMin v CMin Max tng ng vi
LMax v CMax
Chng: Dao ng v sng in t Trang 2
