www.MACeducation.com
I
“Physics M.5 Vol.2”
1123
456
1. 2. 3.
4. 5.
6.
31
(electrostatics)
(Thales of Miletus)
2087 (William Gilbert)
1
(atom) 3
(proton) (neutron) (electron)
(nucleus)
1.1
2 1.1
4
3 1.1
1.1
p n e
(�)
(�)
�e: (�1.602�10�19
C) 0
�e: (�1.602�10�19
C)
1.67262�10�27
kg 1.67429�10
�27 kg
9.10�10�31
kg
(law of conservation of charge)
1 1
2 2 2
1. 2
51
1.2
�
� � �
�
�
�
�
�
�
�
�
�
�
1.1
1 1 2 1 3 2
1 1 1-2
2
3 1-2
6
1.1
1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18
1.3
1.
2 3
1.3
71
2.
- -
-
1.4
3. (C) (A B) C C
1.5
1.5
A B
A
B
A B
A
B
A B
A
B
A
C
BAB
8
1.5 A B C A C B
C A B B
A B
1 6
1.6
1 (electroscope)
1 1 7 2 A
1 7
A
B
B
A
A
B
A B
91
3 1 7
4 1 7 5 A
1 7
A
1.7
A A
2 1. (pith-ball electroscope)
1 8
1.8
A A A
A
10
1.9
1.9
2. (leaf electroscope)
2 1 10
1 11
1.11
B B
� �� �
� �� �
� �� �
��
��
���
�
A
1.10
111
1 12
1.12
1.1
B �
B B
B �
12
1.2
1 2
3
4 5
1 2 3 4 5
1. 2. 3. 4. 5.
131
- (Charles-Augustin
de Coulomb)
(electric force : FE)
2
1 2
3
1.13
2
F � kq1 q2
r2
r
F21�q1
F21 �q1
F21 �q1
F12 �q2
F12�q2
F12�q2
14
F � q1q2
F � 1
r2
q1 q2 r
F � kq1q2
r2
(1.1)
F q1 q2 (N)
q1 q2 (C)
r (m)
k 9 � 109 2
/C2 1
4 �0 �0
(permittivity) 8.854 � 10�12 2
/C2
(1.1) 1
1.3 2 q1 �5 q2 �10
q3 2 a 0.2 q3
q1 � �5 �C, q2 � �10 �C, q3 �
2 �C a � 0.2 nm
q3 q1 q2 q3
F � kq1q2
r2
�q1 �q3 F31
F32
a
a �q2
F31�q3
F32
151
q1 q3
F31 � kq1q3
r213
� (9�109)(5�10
�6)(2�10
�6)
(0.2�10�9
)2
� 2.25�1018
N
q2 q3
F23 � kq2q3
r223
� (9 � 109)(10 � 10
�6)(2 � 10
�6)
(0.2 � 10�9
)2
� 4.5�1018 N
q3 F13 F23
F23 � F
213�F
223
F23 � (2.25�10
18)2�(4.5�10
18)2
F23 � 25.31�10
36
F3 � 25.31�1036 � 5.03�10
18
q3 5.03�1018
1.4 0.53�10
�18
qe � qp � e
FE � kqeqp
r2
FE � ke2
r2 …..(1)
FG � Gmemp
r2
…..(2)
16
(1) (2) FE
FG �
ke2
r2
r2
Gmemp
FE
FG �
ke2
Gmemp
FE
FG �
(9 � 109)(1.6 � 10
�19)2
(6.67 � 10�11
)(9.1 � 10�31
)(1.67 � 10�27
)
FE
FG � 2.27�10
39
2.27 � 10
39
1.5 �q, �q �2q 0, 50 100 50
F � kq1q2
r2
A B
FAB � k(q)(q)
(0.5)2
FAB � kq2
0.25
B C
FBC � k(q)(2q)
(0.5)2
FBC � 2kq2
0.25
B FB � FBC �(�FAB)
FB � 2kq2
0.25 �
kq2
0.25 �
kq2
0.25
FB � 4kq2
N
50 4kq2 C
�q �qFCB FAB �2q
0A
50 cmB
100 cmC
171
1.6 A, B C A 1 � 10�6
A B –1 � 10�6 C AB � AC � 3
A
F � kq1q2
r2
A B
FAB � (9�10
9)(1�10
�6)(1�10
�6)
(3�10�2
)2
FAB � 10 N
A C
FAC � (9�10
9)(1�10
�6)(1�10
�6)
(3�10�2
)2
FAC � 10 N
A FA � FAB2
� FAC2
FA � 102 � 10
2
FA � 10 2 N
A 10 2
FAB
FAC
FA
�1�10�6
C
3 cm
3 cm
�1�10�6
CB
A
C
�1�10�6
C
18
1.7 ABC �4�10�4 �4�10
�4 A B �1.6�10
�18 C C
F � kq1q2
r2
C A
FAC � (9�10
9)(4�10
�4)(1.6�10
�18)
(3�10�2
)2
FAC � 6.4�10�9 N
C B
FBC � (9�10
9)(4�10
�4)(1.6�10
�18)
(3�10�2
)2
FBC � 6.4�10�9 N
C
FC � FAC2
� FBC2
� 2FACFBC cos
FC � (6.4�10�9
)2 � (6.4�10
�9)2 � 2(6.4�10
�9)(6.4�10
�9) cos120º
FC � 6.4�10�9 N
C 6.4�10�9
FBC
FAC
FC
�4�10�4
C 3 cm �4�10�4
C
�1.6�10�18
C
BA
C
60º
60º 60º
191
E)
1. 2. k 3.
12
3
4
5
14Q
d
d
12Q 1Q
E �kQ
r2
E �V
d
20
1
1.14
1.14
1
E �Fq (1.2)
q +1 Q (1.1)
F �kQ(1)
r2
F �kQ
r2
(1.2)
E �kQ
r2 (1.3)
� �
E �Fq
E �kQ
r2
211
1.2
1. - - -
2. 3. 4. 5. 6.
1.
2.
3-5
3. 4. 5. 1-4
1.
2.
3.
22
1.2
1.15
1.15
1.
2.
3.
1.16
1.16 2
231
1.8 5.0�10�15
1.602�10�19
C F � 5�10�15
N
E �Fq
� 5�10
�15
1.602�10�19
� 3.12�104 N/C
3.12�104
1.9 A 6 10
E �kQ
r2
�(9�10
�15)(6�10
�6)
(10�10�2
)2
� 5.4�106 N/C
A 5.4�106
n q1, q2, ..., qn n
E � E1�E2�E3� �En (1.4)
1.10 q1 � q2 � �q q3� �2q (0,0), (2nm, 0) (2nm, 2nm)
(0, 2nm) q 1.6�10�16
r � 10 cm
Q � �6 CA
E
E � E1�E2�E3� �En
�q �q
�2qq3
q2q1
24
E1 q1
E1 � kq1
r21
� (9�10
�15)(1.6�10
�6)
(2�10�9
)2
� 3.6�1011
N/C
E2 q2
E2 � kq2
r22
� (9�10
�15)(1.6�10
�6)
( 8 �10�9
)2
� 1.8�1011
N/C
E3 q3
E3 � kq3
r23
� k(2q)
r23
� (9�10
�15)(2)(1.6�10
�6)
(2�10�9
)2
� 7.2�1011
N/C
E1, E2 E3 x Ex � E3�E2 cos 45º
� (7.2�1011
)�(1.8�1011
) 22
� 5.9�1011
N/C
y Ey � E1�E2 sin 45º
� (3.6�1011
)�(1.8�1011
) 22
� 4.9�1011
N/C
E � Ex2 � Ey
2
� (5.9�1011
)2 � (4.9�10
11)2
� 58�1022 � 7.6�10
11 N/C
(0, 2nm) 7.6�1011
�q �q
�2q
2 nm
45º
2 nm
E3
E1E2
8 nm
q3
q2q1
251
1.11 A C q1 q2 3.6�10
�6 �1.2�10�6
AB 4.6 BC 1.8 B
EAB q1
EAB � kq1
r2AB
� (9�10
�15)(3.6�10
�6)
(4.6)2
� 1.5�103 N/C
q3
EBC � kq3
r2BC
� (9�10
�15)(1.2�10
�6)
(1.8)2
� 3.3�103 N/C
EAB EBC
E � EAB2
� EBC2
� (1.5�103)2 � (3.3�10
3)2
� 13�106 � 3.6�10
3 N/C
tan �
EBC
EAC �
3.3�103
1.5�103
tan � 2.2
� tan�1
(2.2) � 66º
B 3.6�103 66
EAB
q1 q2
q3
A
C
B
q1 � �3.6 C
q2 � �3.6 C
q3 � �1.2 C
A
C
1.8 mEBC
EAB
E
4.6 m
B
26
(neutral point) 2
2
1. 1.17
1.17
2. 1.18
1.18 q1 q2
1.12 �2 �18 20
�q�q1 �q2
E2 E1
E2 E1�q1 �q2 �q
EB EA
20 cm
xA B
�2 C �18 CC
271
C
EA � EB
kqA
r2AC
� kqB
r2BC
qA
r2AC
� qB
r2BC
(2�10
�6)
x2
� (18�10
�6)
(20�x)2
(2�10�6
)(20�x)2 � (18�10
�6)x
2
(20�x)2 � 9x
2
20�x � 3x
x � 5 cm
�2 5
1.13 A B 0.3 A �1
B �0.25 B �0.25
B �0.25
C EA � EB
kqA
r2AC
� kqB
r2BC
qA
r2AC
� qB
r2BC
(1�10
�6)
(30�x)2
� (0.25�10
�6)
x2
(1�10�6
)x2 � (0.25�10
�6)(30�x)
2
x2 � (0.25)(30�x)
2
x � (0.5)(30�x)
1.5x � 15
x � 10 cm
A B B 10
30 cm
A BCEB EA
x
�0.25 C�1 C
28
B �0.25
C
EA � EB
kqA
r2AC
� kqB
r2BC
qA
r2AC
� qB
r2BC
(1�10
�6)
(30�x)2
� (0.25�10
�6)
x2
(1�10�6
)x2 � (0.25�10
�6)(30�x)
2
x2 � (0.25)(30�x)
2
x � (0.5)(30�x)
0.5x � 15
x � 30 cm
A B B 30
1.2
1.19
30 cm
C
EB EA
x
�0.25 C�1 C
A B
291
1.19
q m E
qE
2 F � ma
qE � ma
a � qEm (1.5)
(1.5)
E � Vd (1.6)
V d
E
E
A
VA � 0
d
B
�
�
�
�
�
�
�
�
�
�
�
�
�
�
v
�
E�
�
�
�
�
�
�
�
�
�
�
�
�
�
�q
�qa
a
1.20
a � qEm
E �Vd
30
1.14 1.6
F � 0
qE � meg
qV
d� meg
(1.6�10�19
) V
(1.6�10�2
)� (9.1�10
�31)(10)
V � 9.1�10�13
V
9.1�10�13
E e�
qE
meg
d �
1.6
cm
1. d0 E0 2 2d0
2. 3. 4. q1 � �2 q2 � �2 6
2 5. 2�10
�6 8�10�6
311
(electric potential : V) (J/C) (V)
V � kqr (1.7)
V Q (V)
k 9�109 2
/C2
q (C)
r (m)
�q E
qE B A 1.21
+q A
B B A
A B 1 A B
VB�VA � WA B
q (1.8)
1 1 2 1
V 5 kqr
2
V �kqr
E
F
B
A
qE
�q
1.21 A B
F VB�VA � WA B
q
32
1 �q E �Q A
B 1.22
1.22 �q �Q
A B B A
VB�VA �kQrB
�kQrA
VB�VA � kQ 1rB
�1rB
A B A (VA � 0)
VB�0 � kQ 1rB
�1�
VB �kQrB
� W� B
q
V �kQr (1.9)
V Q (V)
k 9�109 2
/C2
Q (C)
r Q (m)
rB
rA
B
A
F�Q
�q
V �kQr
331
n
i�1Vi � V1�V2�V3�…�Vn (1.10)
q Q
U � kQq
r � qV (1.11)
U q (J)
r (m)
2 3
U � U12�U23�U31
U � kq1q2
r12�
kq2q3
r23�
kq3q1
r31 (1.12)
1.15 �2 �5 10
q � �2�10�6
C, Q � �5�10�6
C r � 10�10�2
m
VA �W� A
q
kQrA
�W� A
q
(9�10
9)(�5�10
�6)
(10�10�2
)�
W� A
(2�10�6
)
W� A � 0.9 J
0.9
n
i�1Vi � V1�V2�V3�…�Vn
U � kQq
r � qV
U � kq1q2
r12�
kq2q3
r23�
kq3q1
r31
10 cmA
�
�5 C
Q
�2 C
q
34
1.16 ABC B BC 3 AB 4 10
�5 �0.6�10�5 A B
C
ABC AC
AC � AB2�BC
2
� 32�4
2 � 5 cm � 5�10
�2 m
A
VAC � kQA
rAC
� (9�10
9)(�10
�5)
(5�10�2
)
� �1.8�106 V
B
VBC � kQB
rBC
� (9�10
9)(�0.6�10
�5)
(3�10�2
)
� �1.8�106 V
C VC � VAC�VBC
� (�1.8�106)�(�1.8�10
6)
� 0 V
C 0
A
C
B4 cm
3 cm
10�5
C �0.6�10�5
C
351
1.17 A, B C 3.0�10�6
, 1.0�10�6
–1.0�10�6 AP 0.6 CP
0.3 BP 0.1 P
P VP � VA�VB�VC
� kQA
rA �
kQB
rB �
kQC
rC
� k QA
rA �
QB
rB �
QC
rC
� (9�109)
(�3�10�6
)
0.6 �
(�1�10�6
)
0.1 �
(�1�10�6
)
0.3
� 1.05�105 V
P 1.05�105
1.18 A, B C �2, �4 �6 P BC Q AB
QC b
2 � a
2�c
2�2ac cos �
QC2 � 60
2�25
2�2(60)(25)cos 53
QC2 � 2,419
QC � 49 cm
P VP � VA�VB�VC
� kQA
rA �
kQB
rB �
kQC
rC � k
QA
rA �
QB
rB �
QC
rC
A BP
C
50 cm
50 cm
A
P
Q
B C60 cm
2 C
�6 C�4 C
40 cm
49 cm
25 cm
25 cm
30 cm30 cm53º
2 CA
CBP�4 C �6 C
Q
36
Q VQ � VA�VB�VC
� kQA
rA �
kQB
rB �
kQC
rC
� k QA
rA �
QB
rB �
QC
rC
� (9�109)
(�2�10�6
)
(25�10�2
) �
(�4�10�6
)
(25�10�2
) �
(�6�10�6
)
(49�10�2
)
� –1.82�105 V
P Q �2.25�105 –1.82�10
5
1.19 q1, q2, q3 q4 d q1 �12 q2 �24 q3 �31 q4 +17 d 1.3
P r
q1 q1q2 q2
q3 q3q4 q4
�d
d
p Pd d
�
� �
�
� �
�
d
r r
r r
d
d
d
P
q3 � �31 nC
q2 � �24 nC
q4 � �17 nC
q1 � �12 nC
371
r r � d2
2
� d2
2
� 2d
2
4
� 22
d � (0.7)(1.3) � 0.91 m
P VP � V1�V2�V3�V4
� kQ1
r � kQ2
r � kQ3
r � kQ4
r
� k Q1�Q2�Q3�Q4
r
� (9�109)
(�12�24�31�17)�10�9
0.91
� 356 V
356
U � U12�U13�U14�U23�U24�U34
� kq1q2
r12 �
kq1q3
r13 �
kq1q4
r14 �
kq2q3
r23 �
kq2q4
r24 �
kq3q4
r34
� k q1q2
r12 �
q1q3
r13 �
q1q4
r14 �
q2q3
r23 �
q2q4
r24 �
q3q4
r34
� k q1q2
d � q1q3
d �
q1q4
2r �
q2q3
2r �
q2q4
d �
q3q4
d
� (9�109) (12�10
�9)(�24�10
�9)
1.3 � (12�10
�9)(31�10
�9)
1.3
� (12�10�9
)(17�10�9
)
(2)(0.91) � (�24�10
�9)(31�10
�9)
(2)(0.91)
� (�24�10�9
)(17�10�9
)
1.3 � (31�10
�9)(17�10
�9)
1.3
� –1.24�10�6
J
–1.24�10�6
38
�1
1.3
1.23 d
WAB � Fd
A B
VAB � VA�VB � WAB
q
VAB � Fdq �
(qE)dq
VAB � Ed (1.13)
1.23 B A +q A B
A B 1.24
A, B C B C
A BC
(equipotential
line) 1.25
1.23
E
F
B
d
A�q
VAB � Ed
1.24 A, B C
E
A C
B
d
S
391
1.25
1.20 2 20 500 10
15 2
E �d
�500
20�10�2
E � 2,500 V/m
2,500
E
E
�
E
�
�
�
�
�
�
�
�
�
�
�
�
�
�
�v
A B
d � 20 cm
V � 500 V
- -
40
u � 0 a � 10
15 m/s
2
v2 � u
2�2aS
v2 � 0�2(10
15)(20�10
�2)
v2 � 4�10
14
v � 2�107 m/s
2�107
1.21 E 20 2�10
�9 A B C
A C WA C � q(VC�VA)
E � d
� VC�VA
d
VC�VA � Ed
WA C � q(Ed)
WA C � (2�10�9
)(20)(10�10�2
)
WA C � 4�10�9
J
4�10�9
(ds) A B V � � 0
(E�ds)
E
A
C
B
10 cm
10 cm
411
1.26
1.27
1.27
1.27
E
�
�
� �
�
�
�
�
�
�
�
�
�
�
�
�
�
�
� �
�
�
�
�
�
�
�
�
�
�
�
�
R R
E
V
R Rr r
Kq
r2
kq
R
kqr
42
1.22 a 10 �1.6×10�6
5 10 14
5 cm
V � kQa
� (9�10
9)(�1.6�10
�6)
10�10�2
� �1.44�105 V
5 �1.44�10
5
10 cm
E � kQ
a2
� (9�10
9)(1.6�10
�6)
(10�10�2
)2
� 1.44�106 N/C
V � kQa
� (9�10
9)(�1.6�10
�6)
10�10�2
� 1.44�105 N/C
10 1.44�106
�1.44�105
14 cm
E � kQ
r2
� (9�10
9)(1.6�10
�6)
(14�10�2
)2
� 7.35�105 N/C
431
V �kQr
�(9�10
9)(�1.6�10
�6)
14�10�2
� �1.03�105 N/C
14 7.35�105
�1.03�105
1.23 10
10�9
1 B A
WBA B A
WB A � q(VA�VB)
� q kQrA
�kQrB
� kQq 1rA
�1rB
� (9�109)(10
�9)(1.6�10
�19)
10.2 �
10.5
� 4.32�10�18
J
1 B A 4.32�10�18
A
B50 cm
10 cm
20 cm
1. 2�10�4
5�10�2
2. Q 8�10�9 Q 10
3.
44
�q
�q
(capacitor)
1.28
2
C � QV
451
d
1.29 d �Q �Q
1.29
2 1.
� �
2.
1(capacitance : C)
C � QV
(1.14)
C (F)
Q (C)
V (V)
C � QV
E
�Q
�Q
d
46
a
V �kQa
QV
�ak
C �ak
(1.15)
t � 0
Q
2 V
W �12
QV (1.16)
U � 12
QV � 12
CV2 �
12
Q2
C (1.17)
1.24 C1 12 C1 250 C2 400 AB
C1
C2
AC C1
C2
AB C1 Q0
Q0 � C1V0
� (250�10�6
)(12)
� 3,000�10�6
C
U �12
Q0V0
�12
(3,000�10�6
)(12)
� 0.018 J
C �ak
W �12
QV
U � 12
QV � 12
CV2 �
12
Q2
C
C1
C2 C
A
B
� �
471
AC Q0 C1 C2
Q1 � C1V
Q2 � C2V
C1 C2 Q0 Q1�Q2 � Q0
V
V � Q0
C1�C2
� 3000�10
�6
(400�250)�10�6
� 4.6 V
C1
Q1 � C1V
� (250×10�6
)(4.62)
� 1.16×10�3
C
C1 1.16×10�3
C2
Q2 � C2V
� (400�10�6
)(4.62)
� 1.85�10�3
C
C2 1.84×10�3
C1
U1 � 12
Q1V1
� 12
(1.16�10�3
)(4.62)
� 2.68�10�3
J
C1 2.68�10�3
C2
U2 � 12
Q2V2
� 12
(1.85�10�3
)(4.62)
� 4.27�10�3
J
C1 4.27�10�3
48
2
1. 1.30
1.30
1.30 2 V C1 Q1 C2 Q2
V1 � V2 � V
Q1 � C1V
Q2 � C2V
Q Q � Q1�Q2
Q � C1V�C2V
Q � (C1+C2)V
(1.14) QV
� C1�C2
C � C1�C2 (1.18)
n
C � C1�C2�C3�….�Cn
C1
C1
C1
V1 � V2 � VC � C1�C2
VV V
�
�
�� �
�
�
�� �
C2
C2Q2
Q1
C2 Cn
C � C1�C2
491
2. 1.31
1.31
V C1
( �Q) C2 ( �Q) V Q �Q C1 �Q
C1 Q �Q C2 �Q C2 Q
V V Q1 � Q2 � Q
V1 �QC1
V2 �QC2
V � V1�V2
V �QC1
�QC2
(1.14) QC
�QC1
�QC2
1C
�1
C1�
1C2
(1.19)
n 1C � 1
C1�
1C2
�1
C3�...�
1Cn
C2C1 Cn
C
��
�Q�Q
C1V1
�Q
�
�Q�Q �Q
�
V2
V V
C2
1C
�1
C1�
1C2
50
1.25
1C � 1
C1�
1C2
1C
� 14
�1
12 �
412
� 13
C � 3 F
3
C � C1�C2
� 4�12
� 16 F
16
C1 C2 C12 � C1�C2
� 1�2 � 3 F
C1 � 4 F
C1 � 1 F
C1 � 3 F
C2 � 2 F
C3 � 2 F
C2 � 6 FC3 � 6 F
C1 � 4 FC2 � 12 F
C2 � 12 F
511
C1 C2 C3
1C � 1
C12�
1C3
1C �
13
�16
� 36
� 12
C � 2 F
2
C1 C2
1
C12 � 1
C1�
1C2
1
C12 �
13
�16
� 36
� 12
C12 � 2 F
C1 C2 C3 C � C12�C3
� 2�2
� 4 F
4
1.26 a A B
� C � CXY � C
A
B
B
AX
C
Y
a a
a a
a�Ca
52
1C
�1
C1�
1C2
1C
�1a�
1a�
1a�C
� 2a�
1a�C
1C
�2(a�C)�a
a(a�C)
aC�a2
� aC2�3aC
2C2�aC�a
2� 0
C x ��b� b
2�4ac
2a
C ��2a� (2a)
2�4(2)(a
2)
2(2)
C �( 3�1)a
2 F
A B ( 3�1)a
2
1. 2. 3.
4. 10 5.
6 F 12 F
V � 36 V
531
1.
1) 2) -
( )
- ( )
3)
4) 3
5)
2.
3.
54
4. 2
1.32
1.33
1.33
1.32
551
1.34
56
1. 2.
1 3.
571
1. 6 2. 3. 4.
5.
1. 5�10 2. 2
30�35
3. 30
4.
58
• 2 •
•
1. 2
2.
3.
•
•
• F �
kq1q2
r2
•
E � kQ
r2
•
� �
591
Process
1. 2. 3.
4.
5.
6.
7.
Attribute
1. 2. 3.
•
• n E � E1 � E2 � E3 �... En
• •
E �
V
d
• V �
kq
r
•
• 2
C � Q
V
• C � C1 � C2 � C3 �... �Cn
• 1
C�
1
C1
�1
C2
�1
C3
�... �1
Cn
60
1. q1:q2
2. �2�104 8�10
�6
3. m �q g �
4. A, B C 3.0�10�6
, 1.0�10�6 -1.0�10
�6 AP � 0.6 CP � 0.3 BP � 0.1 P
5. �10 �40 3 �20
6. A B 0.3 A �1
6.1 B �0.25 6.2 B �0.25
q1 q2
m
E
�
611
7. 0.72 25�10�6 2 Q
6 Q 4
8. A C �12 � AB � 6 BC � 3 B A C B
9. 20 �2 20 2
10. 1 300
B A
11. 12.8 AB
2�108
11.1
11.2
u � 01 cm
Aa
B
� �e�E
E � 2�108 N/C
FE
mg
� � � � � � �
A
B
� � � � � � �
62
12. 3 2 2 �2 �4 3
13 m �q V d
g q 14. A B 25 6 P
5 Q 15 PQ
15. 14 �10�5 Q P
16. A B 6 15 A B
17. 500 25
18. 0.05 F, 400 V 15
19. 5 20 200
19.1
19.2
20. 2 12 1
A
P Q
B� �
5 cm
15 cm
25 cm
6 V