1. The uniform electric field between two conducting charged plates shown in the figure has
a magnitude of
E
= 28.40 N/C. The plate separation is 1 m, and we launch an electron from
the bottom plate directly upward with v
o
= 3
×
10
6
m/s. Will the electron reach the top plate?
Justify your answer by providing numerical data.
*
2
12
31
19
/
10
0
.
5
10
11
.
9
40
.
28
10
6
.
1
s
m
m
qE
a
y
y
×
-
=
×
×
×
-
=
=
-
-
*
(
)
ο
ο
ν
ν
y
y
a
y
y
y
-
=
-
2
2
2
m
H
H
90
.
0
10
0
.
5
2
10
9
0
12
12
=
→
×
×
-
=
×
-
* Since H < 1m, the electron does not reach to the top plate.
2. Three point charges, 1
μ
C each, are placed on three corners of an equilateral triangle with side
a
= 1 m. Write the net electric field at the middle point P, in terms of unit vectors.
2
2
2
2
75
.
0
4
m
a
a
r
=
-
=
*
C
N
k
r
q
k
E
12
2
3
=
=
and
3
3
1
1
3
2
1
E
E
E
E
E
E
E
E
r
r
r
r
r
r
r
r
=
+
-
=
+
+
=
*
C
N
k
E
E
x
x
4
.
10
30
cos
12
3
=
×
=
=
*
C
N
k
E
E
y
y
0
.
6
30
sin
12
3
=
×
=
=
*
(
)
(
)
j
C
N
k
i
C
N
k
E
ˆ
0
.
6
ˆ
4
.
10
+
=
r
y
P
a
x
y
v
o
E
y
x
a
r
E
1
E
2
E
3
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3. A long non-conducting cylinder with radius a = 0.5 m has a
volume charge density
ρ
= -5 nC/m
3
. Find the magnitude of electric
field (in N/C) at a distance r = 0.2 m from its axis.
ο
ε
enc
q
dA
E
=
⋅
∫
r
∫
-
=
rLE
dA
E
π
2
r
LP
r
q
enc
2
π
=
C
N
E
r
E
5
.
56
10
85
.
8
2
2
.
0
10
5
2
12
9
=
→
×
×
×
×
-
-
=
-
=
-
-
ο
ε
ρ
4. A very long line of charge having a uniform charge density
λ
is at a distance of d = 0.4 m from
a positive point charge (Q = 4
μ
C) as shown in the figure. If the net electric field at point A is
zero, find the value of
λ
(sign and magnitude).

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- Spring '07
- exams
- Physics, Charge, Electric charge, 2k, 1m, 0 m, 2 m, Nm2/C
-
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