terry (ect328) – oldhomework 12 – Turner – (59130)
1
This printout should have 13 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
(part 1 oF 2) 10.0 points
±our capacitors are connected as shown in the
fgure.
24
μ
±
57
33
73
94 V
a
b
c
d
±ind the capacitance between points
a
and
b
.
Correct answer: 117
.
9
μ
±.
Explanation:
Let :
C
1
= 24
μ
±
,
C
2
= 33
μ
±
,
C
3
= 57
μ
±
,
C
4
= 73
μ
±
,
and
E
= 94 V
.
C
1
C
3
C
2
C
4
E
B
a
b
c
d
A good rule oF thumb is to eliminate junc
tions connected by zero capacitance.
C
2
C
3
C
1
C
4
a
b
The defnition oF capacitance is
C
≡
Q
V
.
The series connection oF
C
2
and
C
3
gives
the equivalent capacitance
C
23
=
1
1
C
2
+
1
C
3
=
C
2
C
3
C
2
+
C
3
=
(33
μ
±) (57
μ
±)
33
μ
± + 57
μ
±
= 20
.
9
μ
±
.
The total capacitance
C
ab
between
a
and
b
can
be obtained by calculating the capacitance in
the parallel combination oF the capacitors
C
1
,
C
4
, and
C
23
;
i.e.
,
C
ab
=
C
1
+
C
4
+
C
23
= 24
μ
± + 73
μ
± + 20
.
9
μ
±
=
117
.
9
μ
±
.
002
(part 2 oF 2) 10.0 points
What is the charge on the 33
μ
± upper
centered capacitor?
Correct answer: 1964
.
6
μ
C.
Explanation:
The voltages across
C
2
and
C
3
, respectively,
(the voltage between
a
and
b
) are
V
ab
=
V
23
=
94 V
,
and we have
Q
23
=
Q
3
=
Q
2
=
V
ab
C
23
= (94 V) (20
.
9
μ
±)
=
1964
.
6
μ
C
.
003
(part 1 oF 2) 10.0 points
Consider a airflled parallelplate capacitor
with plates oF length 8
.
5 cm, width 6
.
61 cm,
spaced a distance 1
.
01 cm apart.
Now imagine that a dielectric slab with di
electric constant 5
.
6 is inserted a length 4
.
8 cm
into the capacitor.
The slab has the same
width as the plates. The capacitor is com
pletely flled with dielectric material down to
a length oF 4
.
8 cm.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Documentterry (ect328) – oldhomework 12 – Turner – (59130)
2
A battery is connected to the plates so that
they are at a constant potential 0
.
66 V while
the dielectric is inserted.
8
.
5 cm
4
.
8 cm
1
.
01 cm
dielectric
none  air
bottom
1
.
0
dielectric
constant
top
5
.
6
What is the ratio of the new potential en
ergy to the potential energy before the inser
tion of the dielectric?
Edge eFects can be
neglected.
Correct answer: 3
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '09
 Turner
 Energy, Correct Answer, Terry, μF

Click to edit the document details