Lecture8.pdf-Homework Reading: Chap. 26 and Chap.
Showing 12-19 out of 35
Lecture8.pdf-Homework Reading: Chap. 26 and Chap.
Page 12
3/19/2019
12
Kirchhoff’s Loop Law
Parallel Circuit
V
So,
23
24

Page 13
3/19/2019
13
Series Circuit
V
So,
Combinations of Capacitors
If capacitors
C
1
,
C
2
,
C
3
, … are in parallel, their equivalent
capacitance is
If capacitors
C
1
,
C
2
,
C
3
, … are in series, their equivalent
capacitance is
25
26

Page 14
3/19/2019
14
In-Class Activity 8.3
In-Class Activity 8.4
27
28

Page 15
3/19/2019
15
Example 8.2
In the arrangement shown
in the figure, a potential
difference
V
is applied,
and
C
1
the voltmeter between
points
b
and
d
This “balance” occurs
when
C
1
= 4.00
F. If
C
3
= 9.00
F and
C
4
= 12
.
0
F, calculate the value of
C
2
.
Energy Stored in a Capacitor
External work needs to be done in order to
charge a capacitor. Assume at one moment
during the charging of capacitor, the charge is
q
and the potential difference is
U
, if amount
of
dq
charge is moving from one plate to
another, the work done by external force (or
battery) is
The total work done (equal to the total
potential energy gained) by the external
force is
29
30

Page 16
3/19/2019
16
Energy Stored in a Capacitor
Since
Then
So a capacitor separated by electric potential
V
has a
potential energy
Energy Density
We can express
U
in terms of
E
q
and
V
,
The energy density has units J/m
3
.
31
32

Page 17
3/19/2019
17
Energy Density
Interpretation:
placing a charge
Q
on a capacitor
requires external work, or building up a electric field
E
over a volume
requires external work
This works even when there are no
charge present, i.e., the electric
field
E
carries electric energy!
In-Class Activity 8.5
33
34

Page 18
3/19/2019
18
Dielectrics
Gauss’ Law in Dielectrics
: permittivity of the dielectric material
+
q
35
36

Page 19
3/19/2019
19
Figure shows a parallel plate capacitor of plate area
A
and
plate separation
d
. A potential difference
V
0
is applied
between the plates. The battery is then disconnected, and a
dielectric slab of thickness
b
and dielectric constant
is
placed between the plates as shown. Assume
A
= 115 cm
2
d
= 1.24 cm
V
0
= 85.5 V
b
= 0.78 cm
= 2.61
(a)What is the capacitance
C
0
before the dielectric slab is
inserted?
(b) What free charge appears on
the plates?
Example 8.3
(c) What is the electric field
E
0
in the gaps between the plates and
the dielectric slab?
(d) What is the electric field
E
1
in the dielectric slab?
(e) What is the potential difference
V
between the plates after the
slab has been introduced?
(f) What is the capacitance with the slab in place?
37
38

Browse thousands of Study Materials & Solutions from your Favorite Schools
University of Georgia
University_of_Georgia
School:
Physics_2
Course:
Great resource for chem class. Had all the past labs and assignments
Leland P.
Santa Clara University
Introducing Study Plan
Using AI Tools to Help you understand and remember your course concepts better and faster than any other resource.
Find the best videos to learn every concept in that course from Youtube and Tiktok without searching.
Save All Relavent Videos & Materials and access anytime and anywhere
Prepare Smart and Guarantee better grades