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Instructor(s):
PHYSICS DEPARTMENT
Make-up Exam
PHY 2005, Spring 2008
Name (print, last first):
April 14, 2008
Signature:
On my honor, I have neither given nor received unauthorized aid on this examination.
YOUR TEST NUMBER IS THE 5-DIGIT NUMBER AT THE TOP OF EACH PAGE.
(1) Code your test number on your answer sheet (use lines 76–80 on the answer sheet for the 5-digit number).
Code your name on your answer sheet. DARKEN CIRCLES COMPLETELY. Code your UFID number on your
answer sheet.
(2) Print your name on this sheet and sign it also.
(3) Do all scratch work anywhere on this exam that you like. Circle your answers on the test form. At the end of the
test, this exam printout is to be turned in. No credit will be given without both answer sheet and printout.
(4) Blacken the circle of your intended answer completely, using a #2 pencil or blue or black ink. Do not
make any stray marks or some answers may be counted as incorrect.
(5) The answers are rounded off. Choose the closest to exact. There is no penalty for guessing.
(6) Hand in the answer sheet separately.
Physical Constants:
g = 9.8 m/s2
me = 9.11 × 10−31 Kg
mp = 1.67 × 10−27 Kg
e = 1.6 × 10−19 C
constant k in Coulomb’s Law: k = 8.99 × 109 Nm2 /C2
µo = 4π × 10−7 N/A2
εo = 8.85 × 10−12 C2 /Nm2
1. A proton (charge +e, initially at rest) is accelerated through an electric
potential difference of 300 V and enters into a uniform magnetic field
region (shaded region, B = 0.02 T) as shown in the figure. The magnetic
field is applied in the direction perpendicular to the velocity of the
proton entering the region. The electron makes a circular motion in
the field region.
What is the speed of the proton entering in the field region in m/s?
(1) 2.4 × 105
(2) 5.2 × 107
(3) 505.3
B = 0.02 T
r
300 V
(4) 2.7 × 108
(5) 1.6 × 106
2. What is the radius of the proton trajectory in m?
(1) 0.125
(2) 0.032
(3) 0.42
3. Three charges are positioned as indicated in the figure. What are
the horizontal and vertical components (in magnitude) of the net
force exerted on the +13 µC charge by the +15 µC and +11 µC
charges? (horizontal, vertical) in N
(4) 1.52
(5) 0.274
+ 15 µC
0.075 m
37°
+ 13 µC
(1) (129, 312)
(2) (95, 130)
(3) (76, 129)
(4) (250, 130)
0.10 m
(5) (95, 130)
+ 11 µC
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4. A 80-cm long straight wire is moving sideways with a constant
speed perpendicular to a magnetic field of 0.30 T (see figure). The
speed of the wire is 20 m/s. Which of the following statement(s)
is(are) true?
(a) The wire feels a force in the direction perpendicular to its
motion (into the page).
(b) 4.8 V of potential difference is induced across the wire.
(c) The top of the wire has the lower potential.
(d) 1.2 A of current flows through the wire throughout the
motion.
(1) b only
(2) c and d
(3) b and d
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
(4) a and c
5. What is the total power dissipated in the two resistors in the circuit
shown? (in W)
(5) a only
10 Ω
10 V
20 Ω
(1) 15
(2) 10
(3) 67
(4) 670
(5) 30
6. The battery is replaced by an AC source with a 10 V amplitude. What is the total average power dissipated in the
circuit?
(1) 7.5
(2) 10.6
(3) 30
(4) 21.2
(5) need to know the frequency of the AC source.
7. An electron enters a region that contains a magnetic field directed
into the page as shown. The velocity vector of the electron makes
an angle of 30◦ with the +y axis. What is the direction of the
magnetic force on the electron when it enters the field?
(1)
(2)
(3)
(4)
(5)
at an angle of 30◦
out of the page
at an angle of 30◦
at an angle of 60◦
at an angle of 60◦
y
above the positive x axis
below the positive x axis
above the positive x axis
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
8. A 10 turn circular coil has a cross-sectional area of 0.01 m2 .
The coil is located in a variable magnetic field whose behavior
is shown on the graph as a function of time. At all times,
the magnetic field is directed to the normal to the plane of the
loop. Choose section(s) where no induced EMP appears across
the coil.
(1)
(2)
(3)
(4)
(5)
30°
below the positive x axis
x
x
x
x
x
(A) and (C)
(A) only
(B) and (E)
(C) and (D)
none
B (T)
1.5
(A)
(B)
(C)
(D)
(E)
1.0
0.5
Time (s)
0
0.5
1.5
2.0
2.5
9. What is the magnitude of the induced EMF during (D)?
(1) 0.25 V
(2) 0.013 V
(3) 1.25 V
(4) 0.025 V
(5) 0.125 V
3.5
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10. −1 mC charge is moved from A to B to C to D in the presence of
uniform electric field of 1500 N/C as shown in the figure. What is
the net change in electric potential energy in this process?
E = 1500 N/C
B
2m
(1)
(2)
(3)
(4)
(5)
60°
0J
−2.6 J
1.5 J
−1.5 J
7.5 J
2m
A
C
D
11. What is the electric potential difference between B and C? Which point has the higher electric potential?
(1) 1500 V, C is higher. (2) 3000 V, C is higher. (3) 1.5 V B is higher. (4) 1500 V, B is higher. (5) 1.5 V C is higher.
12. There are three capacitors with 8 µF, 4 µF, and 2 µF. They are connected in series across a 14 V battery. What is the
amount of charge on the 4 µF capacitor? (in µC)
(1) 16
(2) 56
(3) 12.2
(4) 196
(5) 97
THE FOLLOWING QUESTIONS, NUMBERED IN THE ORDER OF THEIR APPEARANCE ON THE ABOVE
LIST, HAVE BEEN FLAGGED AS CONTINUATION QUESTIONS: 2 6 9 11