homework_21.1_sol - Homework#3 Solution 12.5 q I JV J D2 Ix...

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
∆
∆ ∆