pan (zp695) – Final exam practice – chiu – (56565)
1
This
print-out
should
have
28
questions.
Multiple-choice questions may continue on
the next column or page – find all choices
before answering.
001
10.0points
An electron and a proton are placed at
locations
A
and
B
respectively. At time
t
= 0,
the electron begins to accelerate as shown,
with the magnitude of acceleration being
a
.
If
e
and
m
p
are the charge and mass of a
proton,
r
is the distance between
A
and
B
,
θ
is the angle shown in the figure and
c
is the
speed of light, what will be the magnitude
and direction of acceleration of the proton a
moment after the electromagnetic waves from
the electron reach
B
?
Note:
Vector
vectorr
has magnitude
r
and di-
rection pointing from
A
to
B
.
Ignore the
electrostatic force between the electron and
the proton
1.
1
4
πǫ
0
e
2
a
cos
θ
m
p
c
2
r
, parallel to
vectora
2.
1
4
πǫ
0
e
2
a
sin
θ
m
p
c
2
r
, parallel to
vectorr
3.
1
4
πǫ
0
e
2
a
sin
θ
m
p
c
2
r
, perpendicular to
vectora
4.
1
4
πǫ
0
e
2
a
sin
θ
m
p
c
2
r
, perpendicular to
vectorr
5.
1
4
πǫ
0
e
2
a
cos
θ
m
p
c
2
r
, parallel to
vectorr
6.
1
4
πǫ
0
e
2
a
cos
θ
m
p
c
2
r
, perpendicular to
vectora
7.
1
4
πǫ
0
e
2
a
cos
θ
m
p
c
2
r
, perpendicular to
vectorr
8.
1
4
πǫ
0
e
2
a
sin
θ
m
p
c
2
r
, parallel to
vectora
002
10.0points
Two long sheets of width
L
= 2
.
2 cm each
contain
N
= 220 closely-packed wires car-
rying current
I
= 12
μ
A in opposite direc-
tions. The sheets are separated by a distance
h
= 174
μ
m. Letting the positive
x
-direction
be to the right, calculate the magnitude of
vector
B
at point
A
located
y
= 48
μ
m above the exact
center of the lower sheet.
Answer in units of T
003(part1of2)10.0points
The switch below is initially set at position
b
. There is no charge nor current around the
right loop while at position
b
. At
t
=
t
0
the
switch is set to position
a
.
L
R
C
E
S
b
a
c
d
What is the potential difference
V
dc
≡
V
c
−
V
d
across the resistor
R
at
t
=
t
0
?
1.
V
dc
=
∞
2.
V
dc
= 0
3.
V
dc
=
E
e
−
1
4.
V
dc
=
E
(1
−
e
−
1
)
5.
V
dc
=
−E

pan (zp695) – Final exam practice – chiu – (56565)
2
6.
V
dc
=
−E
e
−
1
7.
V
dc
=
E
8.
V
dc
=
−E
(1
−
e
−
1
)
9.
V
dc
=
−∞
10.
V
dc
=
E
e
004(part2of2)10.0points
After a long time at position
a
, the switch is
set back to position
b
.
Denote this time as
t
= 0.
What is the maximum energy stored in the
capacitor, expressed in terms of
L
,
E
, and
R
?
(Hint: Use conservation of energy.)
A very long glass rod of length 2
R
carries
a uniformly distributed charge +
q
as shown
in the figure.
A very large plastic disk of
radius
R
, carrying a uniformly distributed
charge
−
Q
is located at a distance
d
from the
rod, where
d << R
. Determine the potential
difference Δ
V
rod
=
V
B
−
V
A
due to the long
rod alone.