Kapoor (mk9499) – homework05 – Turner – (60230)
1
This printout should have 12 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
(part 1 oF 2) 10.0 points
A charged mass on the end oF a light string
is attached to a point on a uniFormly charged
vertical sheet oF infnite extent.
The acceleration oF gravity is 9
.
8 m
/
s
2
and the permittivity oF
Free
space
is
8
.
854
×
10
−
12
C
2
/
N
·
m
2
.
43
.
2 cm
θ
ˆ
ı
ˆ
0
.
33
μ
C
1 g
Areal charge density
0
12
μ
C
/
m
2
±ind the angle
θ
the thread makes with the
vertically charge sheet.
Correct answer: 12
.
8543
◦
.
Explanation:
Let :
g
= 9
.
8 m
/
s
2
,
ǫ
0
= 8
.
854
×
10
−
12
C
2
/
N
·
m
2
,
m
= 1 g = 0
.
001 kg
,
σ
= 0
.
12
μ
C
/
m
2
= 1
.
2
×
10
−
7
C
/
m
2
,
q
= 0
.
33
μ
C = 3
.
3
×
10
−
7
C
,
and
L
= 43
.
2 cm = 0
.
432 m
.
The length
L
oF the string is super²uous.
Let the tension in the string be denoted by
T
. The electric feld due to the infnite sheet
is constant in the
x
direction and is
v
E
=
σ
2
ǫ
0
ˆ
ı .
In the ˆ
ı
and ˆ
directions, Force equilibrium
tells us
T
sin
θ
=
q
·
σ
2
ǫ
0
T
cos
θ
=
m g
tan
θ
=
T
sin
θ
T
cos
θ
=
q σ
2
m g ǫ
0
θ
= arctan
p
q σ
2
m g ǫ
0
P
= arctan
b
(3
.
3
×
10
−
7
C) (1
.
2
×
10
−
7
C
/
m
2
)
2 (0
.
001 kg) (9
.
8 m
/
s
2
)
ǫ
0
B
=
12
.
8543
◦
.
002
(part 2 oF 2) 10.0 points
What value would
σ
in order For he angle 76
◦
?
Correct answer: 2
.
10917
μ
C
/
m
2
.
Explanation:
±rom the previous part, we know
σ
=
2
m g
tan
θ
q
ǫ
0
=
2 (0
.
001 kg)
(
9
.
8 m
/
s
2
)
tan(76
◦
)
3
.
3
×
10
−
7
C
·
(8
.
854
×
10
−
12
C
2
/
N
·
m
2
)
10
6
μ
C
1 C
=
2
.
10917
μ
C
/
m
2
.
003
10.0 points
A net positive charge
Q
is placed on a large,
thin conducting plate oF are
A
.
In electrostatic equilibrium the charge den
sity
σ
on each surFace and the electric feld
E
outside the plate are
1.
σ
=
Q
A
,
E
=
σ
ǫ
0
2.
σ
=
Q
2
A
,
E
= 0
3.
σ
=
Q
2
A
,
E
=
σ
ǫ
0
correct
4.
σ
=
Q
2
A
,
E
=
σ
2
ǫ
0
5.
σ
= 0
,
E
=
σ
ǫ
0
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2
Explanation:
004
10.0 points
A nonconducting plate with infnite dimen
sions carries a uniForm surFace charge density
oF 11
.
72
μ
C
/
cm
2
.
What is the electric feld 5
.
2 cm in Front oF
the plate?
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 Fall '08
 Turner
 Physics, Charge, Mass, Work, Correct Answer, Electric charge, Kapoor

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