Dạng 3 Năng lượng điện trường và năng lượng từ trường

Th
Dạng 3: NĂNG LƯỢNG ĐIỆN TRƯỜNG VÀ TỪ TRƯỜNG
I. PHƯƠNG PHÁP
Áp dụng các công thức sau:
1.



L
W Li=
2.


C
q
W
C
=
.
3.


  

 
  
    
q
q
W Li LI CU
C C

= + = = =
4.
 
I q
ω
=
5.
 
q CU=
Chú ý: !" #$%&≠' !()*+,-%' !%./
!01"2(%.3
   

 
 
C U U RC
I R R
L
ω
= = =P

II. BÀI TẬP VẬN DỤNG
Câu 1:4
5
6
7
8
7
92 %
7

9
7

:

5
 2
5
4
A.; 2
5

5
40
:
 2
5

5
6
:
0<
5
 
5
<
:

:


:
<
:
=
7
>%0
5
<
7
%+
B.?0<
5

:
<
:
8
5
/%<
@
%2
5

@
+
C.?0<
5
 
5
<

:
8
5
/%<
@
%
5
 
5
4+
D.?0<
5
 
5
<
:

:
0<
5

:
<
:
%
:
=
7
%8
:


:
A2
5
8
:
(2
7
%+
Câu 2: !40B$" ! #CD'
A+01 #E/%$%!F+
B+01 #G01C0%292 H+
C+01CE/%$I #+
D+01 #CJ 1=FG+
Câu 3:! ! #C4KI #" #%4G%!8%F" !DF+LM
8N" #$%92 9-G" ! #C+OP>

QR

0010G #B
D G #/D JI #QS

0G !T #D +L-%UG(% 892
/F0G=-%UB01 #CV
A+WX


4R



+ B+WX
C
q



+ C+WX


S


+  D+ W =
L
q



+
Câu 4:! !K!IYG!%!FZ
µ
Q #$92 9-+#% #MD
$ %I #0GR

XQ[\+B !T ##%I>%+
 ]+^_] L+`_] 4+[_] ;+a_]
Câu 5:! !492" #$%Q" ! #CDb !c+#%
#MD d=FIG !T #D >%0010GR

GS


+ -
!T #"eS

f' !0g#% #Md=FI #0G
]+_R

f^+ L+
_
R

f 4+R

f+ ;+
_
R

f^ 
Câu 6:! !40B$"X^Q4X[hYQ #BD JI>

Xa+
i
4+ #
BJI=j_+
i
4'T #" !0g+
]+[+
i`
] L+a+
i`

] 4+_+
i`
] ;++
i`
]
Câu 7:! !KI #" #%
FC
µ
[
=
G%!8" !DFX[+,#/D
I #0Ga\+4 !T # - #/I #=j^\0G
]+Q_]+ L+Q[]+ 4+Qa]+ ;+Q^[]+
Câu 8:4 !T #U !40B$0GXQZ(bcb]c+4%!8" !D
FX[+#% #Md=FI - !T #U=j !
T ##%I0G
]+

\+ L+_\+ 4+
^
\+ ;+Z\+
O03%09k0+,3l`l_[Z_Z
Th
Câu 9: !4" !D+#% #MD d=FI0GR

X\+
-G01 #=j001C'#% #Md=FI0G
]+Q[\+ L+

_

\+ 4+\+ ;+Qa_\+
Câu 10:! !K!IYG!%!F
Z H
µ
Q #$92 9-+#% #M
D $ %I #0GR

XQ[\+B !T ##%I>%+
]+`_]+ L+^_]+ 4+aQl]+ ;+[_]+
Câu 11:% !b4XµYmXQc+ -%
4
X^\'XQ]+4 !D 9%
=j3 ]+^Q[+
n
] L+^Q^`+
n
] 4++
n^
] ;++
n^
]
Câu 12:! ! #CQ%!8%F"#(oDFQ[QI #" #%Q[Y+
" ! #C p%T+ !T #0G]' #/ %I #0G
\+ !T #0G]' #/ %I0G
]+\ L+

\ 4+

\ ;+^\
Câu 13: -= %Q #BI #J !4"BeD >


X
iZ
4+
-I/"M #B0G
µ
(+4 !#%I0G
]+`QZ[]+ L+`ZQ[]+ 4+[Q[[]+ ;+[Q`]+
Câu 14:4 !T #U !4"XQ(b]c+I #
" #%[hY+,!DFJ%!F0G
]+X[ L+X[+
a
−
 4+X[+
Z
−
 ;+X[
Câu 15:! !4QKI #" #%4XZYG!%!8%F" !DFX
+LM#% #MD Ia\+ !T #=ja]Q'#% #Md
%%!F=j+
]+^\ L+[Q\ 4+_Qa\ ;+_\
Câu 16: !4" ! #CDb !cg(o"
^
f(+,#B
D I #0G
il
4+ !T #=ja+
ia
]' #BI #0G
]+Z+

i
4+ L+^+
i
4+ 4++
i
4+ ;+a+
i
4+
Câu 17:! !4"
ω
X
`
f(Q #BD JI>

X^+
i
4+ #BJI>X
+
i
4'T #"e
]+
[
+ A
−
 L+
[
 _+ A
−
 4+
[

+ A
−
;+
[
 + A
−

Câu 18:!I #" #%4XZY 1/ #g #/a\K*g!%!F"X+
4 !T #D >%%!F0G
]+Q]+ L+Q]+ 4+Q]+ ;+]+
Câu 19:! !K%!8%FGI #'#% #MD d=FI #R
4
0#g !T #D S

=$=-%U
]+
C
L
U
C
π


=
L+
4 

R X S
4
4+

4 

R X S
4
;+
4 

R X S
q4
Câu 20:+! !40B$QK%!F%" !DFGI #" #%4+
" ! #CD+OPR

QS

0010G#% #MD d %I #G !T
#D '
A+


S
R
4
=
+ B+
 

R S
4
=
+ C+

 
4
R S

=
+ D+
 
R S 4=
+
Câu 21: +! ! #CK!I #" #%Q[µYG!%!F" !DF
[µ+,#$%J92 9-+,#/D d=FI0G_\+4 !T #D 
0G
A+`Q[

]+ B+[]+ C+`Q[

]+  D+Q[]+
Câu 22:. ! #C4QM% #BD I #0Gr

G !T #D 
0GS

'%9' ! #C0G
A+Xπ>

S

+ B+Xπ+
o
o

q
I
+ C+Xπ4+ D+Xπ
o
o
I
q
+
Câu 23:! ! #s"X[m4X_QZtYQ#% #MD I0GZ\+4 !T
#9#% #MI0G^\"e3
A+[Q[]+ B+Q[]+ C+Q[[]+ D+Q[]+
O03%09k0+,3l`l_[Z_Z
Th
Câu 24: !KI #"4X[YG!%!F"X[µ+,#$%J
92 9-+,#/D d=FI #R

XQ\+4 !T #D 0G
A+a+
i
]+ B+_

]+ C+_

]+ D+a]
Câu 25: Một mạch dao động gồm một cuộn cảm có độ tự cảm L và một tụ điện có điện dung C thực hiện dao
động tự do không tắt. Giá trò cực đại của điện áp giữa hai bản tụ điện bằng U
0
. Giá trò cực đại của cường độ
dòng điện trong mạch là
A. I

0
= U
0
LC
. B. I
0
= U
0
C
L
. C. I
0
= U
0
L
C
. D. I
0
=
LC
U

.
Câu 26: !KI #" #%^[/YG%!8%F" !DF[t+,#/D
$ %I #0G\+4 !T #D 0G
A+Q_]+ B+Qa]+  C+a+
i^
]+ D+_+
i^
]+

Câu 27: !"%!%F" !DFXQQI #" #%4XµY+%
4
X^\
'X_]+'= !S

J !T #+
A+S

X[]+ B+S

X[]+ C+S

X^]+  D+S

X]+
Câu 28: !"%!%FXQQI #" #%4XµY+" !
#C+ #/d=FI0GZ\' !T #0Ga]+4 !T #D 
 !0G
A+S

X[]+ B+S

X^]+C+S

X]+ D+S

XQ]+
Câu 29: !0u$QI #" #%4X[
µ
YQ #BJI"eD 0GZ+

i
[
4+?01 ! #C0G
]+a+
i^
v+ L+QZ+
i^
v+ 4+aQ^+
i^
v+ ;+Z+
i^
v+
Câu 30:; ! #C0G ! p%G+#% #Md %%!F=GQ\
' !T #=jQZ]+4T9#% #Md %%!F=jQl\'
!T #=jQ^]+LM !DFJ%!8X[+,#%JIG01
! #C=j
]+YG[+
i
v+ L+YG_+
i
v+ 4+YG[+
i
v+ ;+YGQ[+
iZ
v+
Câu 31:#% #MD d=FI9% !=ja\Q #%JI=jµY+LM
! #C9%01 1=FGQ01CD E/%$%!F=j
]+Z+
na
v L+Ql+

na
v 4+l+
na
v ;+QZ+
na
v 
Câu 32:!I #" #%
FC
π


_
−
=
 1/!01 #B. e+w% "o=FIG
%%!8%F" !DF
HL
π
[

=
+Lx>% #$8o+w%9F*.=
%8b9-C0yoc01CJ%!8=j_001 #IV
]+f_( L+[f_( 4+f( ;+^f_(
Câu 33:! !4" #$%92 9-QI #" #%Q[tY+; ! #C
bDcJ4g#% #MD $ %I #=ja\+#% #M$ %I #
0G^\'01C=j
]+Q^µv L+Q[µv 4+Qlµv ;+Qµv
Câu 34: !4KI4XaµYG%!F%+LMeD J #/d %I
#0GR


X^\+ - #/d=FJI0G%XZ\01C=j
]+[ZZµv L+_laµv 4+_lQaµv ;+[ZQZµv
Câu 35: !40B$"! ! #CDg(oz

X{+?01
C"e=jseD J"(%d9F0G
]+( L+Q[( 4+Q[( ;+(
Câu 36:40u$(o"3|X+
^
f(QXQ[Q#% #MD =FI
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Câu 38:! ! #C40u$  !g #BD =FDJI #0G
O03%09k0+,3l`l_[Z_Z
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Câu 49:! ! #C" #%JI0G4X^µY+>%' ! #/D 
d=FI0G\+ #/d=FI0Gl\'01CJ0G
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Câu 403! !4"%!%FXQ[GI #4X[tY+#% #MD d
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Câu 44:! !4K%!8"X[GI #"4X[tY+?M% " #$
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]+\ L+_\ 4+\ ;+\
Câu 47 :! !K"%!8%FGI #4%%9+F
00M/01 #I=j01C%!80G3
]+
LC
π
L+

LC
π
4+
^
LC
π
;+
_
LC
π
Câu 48: ! #C4K!%!8%F" !DFGI #" #%
F
µ
π
Q
+B9FC0y#% #MID R

 M0U#% #MI



U
+
V
]+_
s
µ
L+
s
µ
4+
s
µ
;+a
s
µ
Câu 49: !I # 1./!01
J
µ
C%K #!p%"(%. # !
^\+4U(%d9F%
s
µ
'01I #G%!F0=j%+
• e !DFJ%!8V
]+
H
µ
π

_^

L+
H
µ
π

_[
4+
H
µ
π

_
;+
H
µ
π

_
Câu 50: ! #C4K!%!8%F" !DFGI" #%+;%K
#!p%"(%. # !a\%./!01[
J
µ
'U(%9F*
.
s
µ
T ##%+• eV
]+
H
µ

π

_
L+
H
µ
π

aQ
4+
H
µ
π

aQ
;+
H
µ
π

aQ_
O03%09k0+,3l`l_[Z_Z
Th
Câu 51: !40B$Q !T #U=MA/<'X
Q^(
t
ω
b]c+• e4VLMU(%d9F*.Q[
s
µ

'01 #G
01C=j%G=j
J
µ
π
ZQ
+
A.
pF
π
[
B.
pF
π

C.
pF
π

D.
pF
π
[
BÀI TẬP THỰC HÀNH
Câu 1:; ! #C0G ! p%G+#% #Md %%!F=GQ\'
 !T #=jQZ]+4T9#% #Md %%!F=jQl\' !
T #=jQ^]+LM !DFJ%!8X[+,#%JIG01
! #C=j
]+YG[+
i

v+ L+YG_+
i
v+ 4+YG[+
i
v+ ;+YGQ[+
iZ
v+
Câu 2:#% #MD d=FI9% !=ja\Q #%JI=jµY+LM
! #C9%01 1=FGQ01CD E/%$%!F=j
]+Z+
na
v L+Ql+
na
v 4+l+
na
v ;+QZ+
na
v 
Câu 3:!I #" #%
FC
π


_
−
=
 1/!01 #B. e+w% "o=FIG
%%!8%F" !DF
HL
π

[

=
+Lx>% #$8o+w%9F*.=
%8b9-C0yoc01CJ%!8=j_001 #IV
]+f_( L+[f_( 4+f( ;+^f_(
Câu 4:! !4" #$%92 9-QI #" #%Q[tY+; ! #C
bDcJ4g#% #MD $ %I #=ja\+#% #M$ %I #
0G^\'01C=j
]+Q^µv L+Q[µv 4+Qlµv ;+Qµv
Câu 5: -= %Q #BI #J !4"BeD >

X
iZ
4+
-I/"M #B0G
µ
(+4 !#%I0G
]+`QZ[]+ L+`ZQ[]+ 4+[Q[[]+ ;+[Q`]+
Câu 6:4 !T #U !4"XQ(b]c+I #"
#%[hY+,!DFJ%!F0G
]+X[ L+X[+
a
−
 4+X[+
Z
−
 ;+X[
Câu 7:! !4QKI #" #%4XZYG!%!8%F" !DFX
+LM#% #MD Ia\+ !T #=ja]Q'#% #Md

%%!F=j+
]+^\ L+[Q\ 4+_Qa\ ;+_\
Câu 8: !4" ! #CDb !cg(o"
^
f(+,#BD
I #0G
il
4+ !T #=ja+
ia
]' #BI #0G
]+Z+
i
4+ L+^+
i
4+ 4++
i
4+ ;+a+
i
4+
Câu 9:4 !T #U! !0G
cb([Q Ati
π
=
+#(oDFJ%!
80G+.


=
π
+,#%G=-%U #BJI #"eG(% 8V

]+
FC

+[
−
=
G
ccb

(b
+[
^
Ctq
π
π
π
−=
−
L+
FC
_
+[
−
=
G
ccb

(b
+[
^

Ctq
π
π
π
−=
−
4+
FC
_
+[
−
=
G
ccb

(b
+[
^
Ctq
π
π
π
+=
−
;+
FC

+[
−
=

G
cb(
+[
^
Ctq
π
π
−
=
Câu 10: !0B$4KI #" #%[YG%!8" !IF+;T #
=MA/<'XQ(Zb]c+B01 #G -
st
^Z
π
=
V
]+_ZQ[
J
µ
L+_lQ[
J
µ
4+l_Q`[
J
µ
;+_aQ[
J
µ
O03%09k0+,3l`l_[Z_Z