Homework #3 Solution
12.5
J
J
J
electron
J
q
At
J
I
A
J
J
J V
x
J
A J
J
D
2
4
2
Ix
J
J V
J
D
2
2
4
Ix
JJ
J V
J
42 10
3
A2 10000m
2
2 5.82 10
7
C
2
J 2s2m
2
2
2
2
2
2
2
2
2
2
2
2
2 200V
2 1.09762 10
2 3
m
2
2
D J
3.31cm
The required wire diameter is about 3.31 cm.
12.6
J
J
J
diffusion
J
M
At
J
J
J C
x
J
M
t
J
J
J
D
2
2
C
4
x
J
1.772 10
2 9
m
2
s
2
2
2 1m
2
2
0.000422 0
2
2
kg
m
3
42 0.01m
2 5.842 10
2 11
kg
s
The rate at which carbon dioxide diffuse to the algae is
2
5.842 10
2 11
kg
s
.
12.7
(a) Series:
R
S
=
R
1
+
R
2
=
5
Ω +
10
Ω =
15
Ω
(b) Parellel:
R
P
=
1
1
R
1
+
1
R
2
=
1
1
5
Ω
+
1
10
Ω
=
10
3
Ω ≈
3.33
Ω
12.8
R
equiv
=
1
1
R
1
+
1
R
2
+
R
3
=
1
1
20
Ω
+
1
10
Ω
+
5
Ω =
20
3
Ω +
5
Ω =
35
3
Ω ≈
11.67
Ω
12.13
Let assume the heat resistance of each panel is the same, and denoted as R.
Case I: uniformly covered with three layers
,
,1
1000
3 ,
,
1000
3
3
panel
panel
heat
heat total
panel
heat
panel
TA
T
T
R
R J
Q
A
J
R
R
R
∆
∆
∆
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- Spring '08
- V
- Molecular diffusion, carbon dioxide diffuse, Qheat, Apanel J heat
-
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