Chapter 24
24.1
A particular 12V car battery can send a total charge of 84 Ah through a circuit from one
terminal to the other.
(a)
How many coulombs of charge does this represent?
(b)
If this entire
charge undergoes a potential difference of 12V, how much energy is involved.
q
=
84
A
⋅
h
⋅
3600
s
1
h
=
3.024
×
10
5
C
Δ
U
=
q
Δ
V
=
3.024
×
10
5
C
⋅
12
V
=
3.63
×
10
6
J
24.5
Two large, parallel, conducting plates are 12 cm apart and have charges of equal magnitude
and opposite sign on their facing surfaces.
An electrostatic force of 3.9
×
10
−
15
N
acts on an
electron placed anywhere between the two plates (Neglect fringing.)
(a)
Find the electric field at
the position of the electron.
(b)
What is the potential difference between the plates.
Since the force on an electron is known everywhere, we can find the field
F
=
q E
E
=
F
q
=
3.9
×
10
−
15
N
1.6
×
10
−
19
C
=
2.4375
×
10
4
N
/
C
Since the field is due to parallel plates, we can now calculate the potential difference between the
plates from the field.
V
=
E
⋅
d
=
24,375
N
C
⋅
0.12
m
=
2925
V
24.7
An infinite nonconducting sheet has a surface charge density
σ
=
5.80
pC
/
m
2
.
(a) How
much work is done by the electric field due to the sheet if a particle of charge
q
=
1.60
×
10
−
19
C
is
moved from the sheet to a point P at a distance
d
=
3.56
cm
from the sheet.
(b) If the electric
potential V is defined to be zero on the sheet, what is V at P?
E
=
σ
2
ε
0
W
=
F
⋅
d
=
q Ed
=
q
σ
d
2
ε
0
=
1.87
×
10
−
21
J
V
(
z
)
−
V
0
=
−
σ
2
ε
0
0
z
∫
dz
V
(
z
)
−
V
0
=
σ
2
ε
0
z
V
(
z
)
=
V
0
−
σ
2
ε
0
z
=
0
−
0.0167
=
−
0.01167
V
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24.8
A graph of the x component of the electric field as a function of x in a region of space is
shown in Fig. 2430.
The scale of the vertical axis is set by
E
xs
=
20
N
/
C
.
The y and z
components of the electric field are zero in this region.
If the electric potential at the origin is 10V,
(a) what is the electric potential at
x
=
2.0
m
(b)
What is the greatest positive value of the electric
potential for points on the x axis for which
0.0
≤
x
≤
6.0
and (c) for
what value of x is the electric
potential zero.
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 Spring '07
 Ndili
 Charge, Electric charge, 1.0M, 0.12M, 2431a, 0  L

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