lim (kl9356) – Homework 7 – Weathers – (22202)
1
This printout should have 10 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
10.0 points
Two conductors insulated From each other are
charged by transFerring electrons From one
conductor to the other. AFter 2
.
274
×
10
14
have been transFerred, the potential di±erence
between the conductors is 15
.
7 V.
The
charge
on
an
electron
is

1
.
60218
×
10
−
19
C
.
What is the capacitance oF the system?
Correct answer: 2
.
3206
×
10
−
6
².
Explanation:
Let :
e
=

1
.
60218
×
10
−
19
C
,
N
= 2
.
274
×
10
14
electrons
,
and
V
= 15
.
7 V
.
One conductor gains a charge oF
Q
=

N e
while the other gains a charge oF

Q.
The capacitance oF the system is
C
=
q
V
=

N e
V
=

(2
.
274
×
10
14
) (

1
.
60218
×
10
−
19
C)
15
.
7 V
=
2
.
3206
×
10
−
6
²
.
002
10.0 points
A spherical capacitor consists oF a conducting
ball oF radius 15 cm that is centered inside a
grounded conducting spherical shell oF inner
radius 17 cm.
What charge is required to achieve a
potential oF 1452 V on the ball oF ra
dius 15 cm?
The Coulomb constant is
8
.
98755
×
10
9
N
·
m
2
/
C
2
.
Correct answer: 2
.
05985
×
10
−
7
C.
Explanation:
Let :
k
e
= 8
.
98755
×
10
9
N
·
m
2
/
C
2
,
a
= 15 cm = 0
.
15 m
,
b
= 17 cm = 0
.
17 m
and
V
= 1452 V
.
The capacitance oF a spherical capacitor is
given by
C
=
a b
k
e
(
b

a
)
. The charge required
to achieve a potential di±erence
V
between
the shell and the ball is given by
Q
=
C V
=
1
k
e
a b V
(
b

a
)
=
1
(8
.
98755
×
10
9
N
·
m
2
/
C
2
)
×
(0
.
15 m) (0
.
17 m) (1452 V)
(0
.
17 m)

(0
.
15 m)
=
2
.
05985
×
10
−
7
C
.
keywords:
003
(part 1 oF 2) 10.0 points
A 22 m length oF coaxial cable has a solid
cylindrical wire inner conductor with a di
ameter oF 2
.
633 mm and carries a charge oF
7
.
62
μ
C.
The surrounding conductor is a
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 Spring '00
 Littler
 Charge, Magnetism, Work, lim, Correct Answer, Electric charge, C2 /N, CBC

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