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PHYSICS DEPARTMENT
PHY 2054
D. Reitze
3rd Exam
Name (print):
November 30, 1999
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.
DIRECTIONS
(1) Code your test number on your green answer sheet (use 76{80 for the 5-digit number). Code your name
on your answer sheet. Darken circles completely (errors can occur if too light). Code your student 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. 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 with scratch work most questions demand.
(4) Work the questions in any order. Incorrect answers are not taken into account in any way; you may guess at answers
you don't know if you feel that a correct answer is listed. Guessing on all questions will most likely result in failure.
(5) If none of the answers is correct, please leave the answer sheet blank. It is not our intention to omit the right answer,
but in case of a mistake, please leave the answer sheet blank.
(6) Blacken the circle of your intended answer completely, using a number 2 pencil. Do not make any stray
marks or the answer sheet may not read properly.
(7) As an aid to the examiner (and yourself), in case of poorly marked answer sheets, please circle your selected answer
on the examination sheet.
(8) Good luck!!!
>>>>>>>>WHEN YOU FINISH <<<<<<<<
Hand in the green answer sheet separately.
CONSTANTS
k = 1=(4¼²o ) = 9:0 £ 109 N m2 / C2 ²0 = 8:85 £ 10¡12 C2 / (N m2 )
g = 9:8 m/s2
e = 1:6 £ 10¡19 C
electron mass: mp = 9:11 £ 10¡31 kg proton mass: mp = 1:67 £ 10¡27 kg
p = 10¡12
n = 10¡9
¹ = 10¡6
¹0 = 4¼ £ 10¡7 TAm
m = 10¡3
K = 103
c = 3 £ 108 m/s
1. A rectangular loop carrying 10 A current is located near a long straight wire carry 15 A current as shown in Figure 1.
What is the net force (in N) on the loop?
(1)
(2)
(3)
(4)
(5)
1:0 £ 10¡4
3:2 £ 10¡2
3:2 £ 10¡2
5:8 £ 10¡3
2:1 £ 10¡5
directed
directed
directed
directed
directed
toward straight wire
away from straight wire
toward straight wire
away from straight wire
toward straight wire
2. Three wires carry current perpendicular to the page (see Figure 2). Each wire carries the same current. Find the
direction of the force on wire 3.
(1) 0±
(2) 180±
(3) 270±
(4) 60±
(5) 330±
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3. A long wire is bent such that a portion of it forms 5 circular loops of 10 cm radius (See Figure 3). The B ¯eld at the
center of the loop is determined to be 0.01 T. What is the current in wire (in A)?
(1) 300
(2) 100
(3) 30
(4) 15
(5) 230
4. A plane °ying over the North Pole at a speed of 720 km/hr experiences an induced current of 0.5 V across its wings.
What is the magnitude of the magnetic ¯eld (in T) at the North Pole? Assume that the magnetic ¯eld is perpendicular
to the surface and that wingspan of the plane is 35 m.
(1) 7:1 £ 10¡5
(2) 3:2 £ 10¡3
(3) 6:0 £ 10¡4
(4) 8:1 £ 10¡2
(5) 8:1 £ 10¡1
5. In Figure 4a, wire loop #1 is traveling toward a long straight wire with current as shown. In Figure 4b, wire loop #2
is leaving the magnetic ¯eld region as shown. Which statement is TRUE?
(1)
(2)
(3)
(4)
(5)
The induced current in loop #1
The induced current in loop #1
The induced current in loop #1
The induced current in loop #1
Not enough information given.
is
is
is
is
clockwise; the induced current in loop #2 is clockwise.
counterclockwise; the induced current in loop #2 is clockwise.
counterclockwise; the induced current in loop #2 is counterclockwise.
clockwise; the induced current in loop #2 is counterclockwise.
6. The DirectTV satellite radiates 100 MW of average power equally in all directions. What is the magnitude of the
peak electric ¯eld (in V/m) at a distance of 40000 km (on the surface of the earth)?
(1) 0.002
(2) 2
(3) 28
(4) 0.01
(5) 0.28
7. The Zorgon mothership has aimed her dreaded Z-ray blaster at Gainesville. If the pulse generated by the blaster has
an intensity of 106 W/m2 and duration of 10¡18 s, how much energy is in the pulse (in J)? Assume Gainesville has a
1000 km2 area.
(1) 1:0 £ 10¡3
(2) 3:4 £ 1012
(3) 7:8 £ 106
(4) 1:2 £ 10¡5
(5) 9:0 £ 10¡1
8. Which of the ray tracing diagrams in Figure 5 is INCORRECT?
(1) II
(2) I,II
(3) I
(4) I,III
(5) III
9. Three polarizers are oriented such that the relative angle between the each of the transmission axes of the polarizers
is the same. If 10% of the initially unpolarized light is transmitted through the ¯nal polarizer, what is the angle (in
degrees)?
(1) 48±
(2) 26±
(3) 67±
(4) 19±
(5) 33±
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10. A wire loop is located in a magnetic ¯eld. Which of the following situations would NOT result in an induced current
in the wire loop?
(1)
(2)
(3)
(4)
(5)
The
The
The
The
The
magnetic
magnetic
magnetic
magnetic
magnetic
¯eld
¯eld
¯eld
¯eld
¯eld
is
is
is
is
is
directed
directed
directed
directed
directed
parallel to the plane of the loop; the area of the loop increases with time.
perpendicular to the plane of the loop; the magnetic ¯eld increases with time.
perpendicular to the plane of the loop; the area of the loop decreases with time.
perpendicular to the plane of the loop, the area of the loop increases with time.
at 45 to the plane of the loop, the magnetic ¯eld decreases with time.
11. A 1.5 m long, 0.6 kg conducting rod slides down between two vertical conducting rails at a constant speed (See Figure
6). A 4.3 T magnetic ¯eld is directed perpendicular to the plane of rails. A 4- resistor is attached to the top of the
rails. What is the velocity of the rod (in m/s)?
(1) 0.57
(2) 2.32
(3) 3.22
(4) 0.23
(5) 1.99
12. Which of the following statements is TRUE?
I. The E,B ¯elds in an electromagnetic wave are always perpendicular to the direction of travel.
II. The speed of electromagnetic waves in a vacuum depends on the wavelength.
III. Electromagnetic waves carry energy.
(1) I,III
(2) I,II,III
(3) II,III
(4) III
(5) I
13. Figure 7 shows several di®erent antenna con¯gurations. Which con¯guration(s) would have the best reception for the
electromagnetic wave propagating in the z-direction?
(1) II, III
(2) II
(3) III
(4) I, II
(5) I, III
14. What is the angle (in degrees) between the input and the output rays shown in Figure 8.
(1) 40±
(2) 25±
(3) 60±
(4) 90±
(5) 75±
15. A concave mirror with a 50 cm radius of curvature forms an image with a magni¯cation of ¡2:5. How far is the object
located from the mirror (in cm)?
(1) 35
(2) 15
(3) 50
(4) 88
(5) 45
16. Two electromagnetic waves have a frequency di®erence of 1 MHz and a wavelength di®erence of 10¡3 m. What are
the wavelengths of the electromagnetic waves (in m)?
(1) 0.547, 0.548
(2) 0.173, 0.174
(3) 0.001, 0.002
(4) 0.022, 0.023
(5) 0.232, 0.332
17. A single turn wire loop 1 cm in diameter is placed inside a 100turn/cm solenoid as shown in Figure 9. The current in
the solenoid is increases linearly from 0 A to 4 A in 5 £ 10¡6 s. What is the average induced current in the loop (in
V) during the 5 £ 10¡6 s interval? (B = ¹0 nI for a solenoid)
(1) 7:9 £ 10¡3
(2) 2:9 £ 10¡3
(3) 6:0 £ 10¡3
(4) 1:8 £ 10¡3
(5) 7:1 £ 10¡3
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18. An object is placed in front of a concave mirror such that the magni¯cation is ¡4. Which statement is CORRECT?
(1)
(2)
(3)
(4)
(5)
The
The
The
The
The
object lies in between the focal point and the radius of curvature of the mirror.
object lies within the focal point of the mirror.
object lies beyond the radius of curvature of the mirror.
image is real and upright.
image is virtual and inverted.
19. An object is placed 25 cm in front of a convex mirror. The resulting image has a magni¯cation of + 0.25. What is
the radius of curvature of the mirror (in cm)?
(1) 16.67
(2) 8.34
(3) 33.33
(4) 4.17
(5) 66.66
20. Please check again that you have correctly bubbled in your NAME, SOCIAL SECURITY NUMBER, and EXAM
CODE. Which of the following statements is correct?
(1)
(2)
(3)
(4)
(5)
I have correctly bubbled in this information. (If you haven't, this question will be marked wrong!!)
I'm still despondent over the UF-FSU game; I can't bring myself to do anything... .
Can't do it because of three words: \Too much turkey!"
I'm doing so well in this class I can a®ord to squander points.
If I bubble it in perfectly within the circles, could I get 10 points extra credit??
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