Munoz (gm7794) – HW02 – TSOI – (92515)
1
This
printout
should
have
16
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001
10.0 points
The diagrams below depict three electric field
patterns.
Some of these patterns are physi
cally impossible.
Assume these electric field patterns are due
to static electric charges outside the regions
shown.
(a)
(b)
(c)
Which electrostatic field patterns are phys
ically possible?
1.
(b) and (c)
2.
(a) and (c)
3.
(a) and (b)
4.
(a) only
5.
(c) only
6.
(b) only
correct
Explanation:
Electrostatic lines of force do not intersect
one another.
Neither do they form a closed
circuit (unless there is a changing magnetic
field present).
002
10.0 points
Given symmetrically placed rectangular insu
lators with uniformly charged distributions of
equal magnitude as shown in the figure.
x
y
+ + + + + +
+ + + + + +
     
In this figure, at the origin, the net field
E
net
is
1.
zero and the direction is undefined.
2.
along 30
◦
direction in the first quadrant.
3.
aligned with the positive
x
axis.
4.
aligned with the negative
y
axis.
correct
5.
along 225
◦
direction in the first quad
rant.
6.
aligned with the negative
x
axis.
7.
along 60
◦
direction in the first quadrant.
8.
along 135
◦
direction in the first quad
rant.
9.
aligned with the positive
y
axis.
10.
along 45
◦
direction in the first quadrant.
Explanation:
At the origin the fields from the bottom slab
points towards the negative
y
axis (towards
the negatively charged slab).
The field from the right and left slabs have
equal magnitudes at the origin and are sym
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Munoz (gm7794) – HW02 – TSOI – (92515)
2
metric about the
y
axis.
The field from the
right and left slabs point away from each pos
itively charged slab. Therefore the
x
compo
nent of the field cancels at the origin.
The
net field from the right and left slabs points
towards the negative
y
axis (away from the
positively charged slab).
Hence, the sum of the electric fields from all
three slabs is aligned with the negative
y
axis.
003
(part 1 of 2) 10.0 points
A dipole (electrically neutral) is placed in an
external field.
+
(a)
+
(b)

+

+
+
+
+
+
+
+
+
+
+
+
+
+
+


























+
+
+
+
+
+
+
+
+
+
+
+
+

+

+
(c)
(d)
For which situation(s) shown above would
the net force on the dipole be equal to zero?
1.
(
b
) only
2.
(
a
) and (
b
)
3.
(
c
) only
4.
(
a
) only
5.
(
a
) and (
d
)
6.
(
b
) and (
d
)
7.
(
c
) and (
d
)
correct
8.
(
d
) only
9.
(
b
) and (
c
)
10.
(
a
) and (
c
)
Explanation:
The force on a charge in the electric field is
given by
F
=
q E
and the torque is defined as
T
=
r
×
F
Δ
E
=
k
Δ
q
r
2
ˆ
r
E
=
Δ
E
i
.
Symmetry of
the
configuration
will cause
some component of the electric field to be
zero.
Gauss’ law states
Φ
S
=
E
·
dA
=
Q
0
.
The electric dipole consists of two equal and
opposite charges separated by a distance. In
either situation (
c
) or (
d
), the electric field
is uniform everywhere between the parallel
infinite plates.
Thus, the electric force on
one charge is equal but opposite to that on
another so that the net force on the whole
dipole is zero. By contrast, electric fields are
nonuniform for situations both (
a
) and (
b
).
This is the end of the preview.
Sign up
to
access the rest of the document.
 Summer '08
 morrison
 Physics, Charge, Electric charge, N/C, Munoz

Click to edit the document details