Download physics 100 prac exam#4

physics 100 prac exam#4
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1.
Electrons flow around a circular wire loop in a horizontal plane, in a direction that is clockwise when
viewed from above. This causes a magnetic field. Inside the loop, the direction of this field is
A. up.
B. down.
C. toward the center of the loop.
D. radially outward from the center of the loop.
2.
A horizontally moving positive sodium ion enters a magnetic field that points up. The magnetic force
pushes the charge out of its original path.
When viewed from the perspective of the charge, what direction will the magnetic force point?
A. Left, into the page.
B. Right, out of the page.
C. Not enough information to answer.
3.
A current flowing through a long, straight wire causes a magnetic field that points
A. radially outward from the wire.
B. radially inward toward the wire.
C. along the wire.
D. along concentric circles around the wire.
4.
A little magnetic compass has a needle whose tips are clearly labeled N and S. The compass is placed
next to a single circular loop of wire lying flat on a wooden table. The
current in the loop is clockwise. What happens?
A. The N tip of the needle is attracted toward the loop.
B. The S tip of the needle is attracted toward the loop.
C. The needle orients itself with the N tip pointing in the direction of the current in the segment of the
loop closest to the needle.
D. The needle orients itself with the S tip pointing in the direction of the current in the segment of the loop
closest to the needle.
E. None of these.
5.
Two identical coils of wire are placed on a single horizontal wooden broom handle. The coils are
separated by a few centimeters. We now run identical currents in the same direction through each coil.
The coils experience
A. no forces because the currents are identical.
B. an attractive magnetic force.
C. a repulsive magnetic force.
D. an attractive electrostatic force because one coil is negatively charged and the other positively charged.
E. a repulsive electrostatic force because both coils are identically charged.
6.
Which of the following cannot induce a voltage in a loop of wire?
A. Expanding or contracting the loop in a region where there is no magnetic field.
B. Moving the loop near a magnet.
C. Moving a magnet near the loop.
D. Changing the current in a nearby loop.
7.
The south pole of a bar magnet is moved toward an aluminum ring, along the axis of the ring. As the
magnet approaches, the changing magnetic flux induces an electric current in the ring that, when seen
from the bar magnet, corresponds to positive charge carriers flowing
A. clockwise.
B. counterclockwise.
C. alternating with a fixed frequency.
D. alternating with a frequency proportional to a speed of the bar magnet.
8.
A horizontal straight wire carries a current from south to north. The resulting magnetic field lines are
A. parallel to the wire from south to north.
B. parallel to the wire from north to south.
C. closed circles perpendicular to the wire directed clockwise as viewed from the south.
D. closed circles perpendicular to the wire directed counterclockwise as viewed from the south.
E. straight lines perpendicular to the wire.
9.
Imagine a magnetic field pointing into the plane of this page. An electron moves across the paper from
left to right. The direction of the magnetic force on the electron will be
A. into the plane of the paper.
B. out of the plane of the paper.
C. in the plane of the paper and toward the top of the page.
D. along the edge of the paper opposite the electron's velocity.
E. in the plane of the paper and toward the bottom of the page.
10. A transformer has 200 turns on the primary and 20 turns on the secondary. The primary is connected to a
direct current source of 100 millivolts. The voltage in the secondary coil will be
A. 10 millivolts.
B. 20 millivolts.
C. 1000 millivolts.
D. 4000 millivolts.
E. zero.
11. Electromagnetic waves are generally
A. transverse waves.
B. longitudinal waves.
C. a 50/50 combination of transverse and longitudinal waves.
D. standing waves.
12. The period and the frequency of a sound wave are
A. reciprocals of each other.
B. independent of each other.
C. multiples of each other—period is 2p times the frequency.
D. none of these.
13. The Doppler effect refers to changes in a sound wave's
A. frequency caused by a change in speed of sound.
B. frequency caused by motion of a source or receiver.
C. amplitude caused by a change in speed of sound.
D. amplitude caused by motion of a source or receiver.
14. If the speed of sound is 1100 feet per second and a tuning fork oscillates at 440 cycles per second, what is
the wavelength l of the sound produced?
A. 11 feet.
B. 4.4 feet.
C. 0.4 foot.
D. 2.5 feet.
15. On a day when the speed of sound in air is 340 m/s, a lightning bolt is observed and the resultant
thunderclap is heard 2 seconds afterwards. About how far away was the lightning bolt?
A. 170 m.
B. 680 m.
C. 1020 m.
D. 1700 m.
16. As a wave passes from one medium into another, it often happens that its speed increases with no change
in frequency. Under these circumstances, the wavelength
A. decreases.
B. stays the same.
C. increases.
17. Two musical strings have the same length and tension, but string A has one fourth the mass of string B.
The speed of a wave on string A is
A. one fourth the speed of a wave on string B.
B. one half the speed of a wave on string B.
C. twice the speed of a wave on string B.
D. four times the speed of a wave on string B.
E. the same as the speed of a wave on string B.
18. To change the fundamental frequency of a guitar string, you can
A. make it shorter, by pressing a finger of your left hand on the string.
B. strum it over the sound hole.
C. use something other than a pick.
D. do nothing short of using a completely different guitar.
19. The principle of superposition tells us that, if two waves cross paths,
A. the frequency is the sum of the individual frequencies.
B. the amplitude is the sum of the individual amplitudes.
C. the wavelength is the sum of the individual wavelengths.
D. the speed is the speed of the faster wave.
20. A string is held taut between two supports 4.0 m apart. The two longest possible wavelengths for standing
waves are
A. 4 m and 2 m.
B. 6 m and 3 m.
C. 8 m and 4 m.
D. 16 m and 5.3 m.
21. Which of the following is not an electromagnetic wave?
A. Sound.
B. Microwaves.
C. Infrared.
D. X-ray.
E. Light.
22. The primary difference between infrared and visible light is that
A. they have different amplitudes.
B. infrared travels faster than visible light.
C. they have different wavelengths.
D. infrared does not have a magnetic field associated with its electric field.
E. no materials currently known have the ability to reflect infrared.
23. For visible light, which property of visible electromagnetic waves changes with color?
A. Amplitude.
B. Frequency.
C. Wavelength.
D. Amplitude and frequency.
E. Frequency and wavelength.
24. The frequency of blue light is ______ that of green light.
A. greater than
B. less than
C. the same as
D. greater than, the same as, or less than, depending on a source of light
25. If a surface is illuminated by magenta light and the red is absorbed, then the color of the surface will
appear as
A. green.
B. blue.
C. yellow.
D. red.
26. The daytime sky is blue, on sunny days, because the atmosphere
A. is most efficient at scattering red light.
B. absorbs blue light.
C. is more efficient at scattering blue light.
D. absorbs the red light.
E. contains small amounts of water vapor that give the air its blue color.
27. Electromagnetic waves that travel through a vacuum are not
A. transverse waves.
B. longitudinal waves.
C. able to propagate, since there is no atmosphere.
D. oscillating.
28. The evening sunsets are reddish orange because the atmosphere
A. is most efficient at scattering red light.
B. absorbs blue light.
C. is more efficient at scattering blue light.
D. absorbs the red light.
E. contains small amounts of red dust that give the air its red color.
29. EM waves tend to be scattered the most by an object that is
A. magnetic.
B. a liquid.
C. conducting.
D. about the same size as the wave.
E. reflective.
30. A property of electromagnetic waves that makes them different than other kinds of waves such as sound
or water waves is that
A. they are transverse waves.
B. they do not require a medium.
C. their speed can change when moving in different media.
D. they have many possible wavelengths.
31. When light enters a medium with a higher index of refraction it
A. is absorbed.
B. is bent away from the normal.
C. is bent towards the normal.
D. continues in the same direction.
32. Light is refracted as it crosses the interface between two different media because
A. it changes speed.
B. it changes frequency.
C. it becomes polarized.
D. it loses energy.
33. When light is reflected from a smooth, plane mirror
A. most of the light is scattered into multiple directions.
B. the angle of reflection is the same as the angle of incidence.
C. the light is changed to a lower frequency.
D. the wave characteristics are predominant.
34. A converging lens
A. always has a real image.
B. refracts all light toward the focal point.
C. always has two curved surfaces.
D. is thicker in the center than the edges.
35. Light from the sun passes through a converging lens and forms an image at
A. infinity.
B. the focal point.
C. the center of the lens.
D. the center of curvature of the lens.
36. A plane mirror will always produce a
A. real, erect image.
B. virtual, inverted image.
C. real, inverted image.
D. virtual, erect image.
37. A shaving mirror and a make-up mirror both magnify the image. Thus, these mirrors are ___________
mirrors.
A. concave
B. convex
C. plane
38. The rearview mirror of an auto bears the legend "Objects in mirror are closer than they appear." This
mirror is a ______ mirror.
A. concave
B. convex
C. converging
D. plane
39. A ray of light moves from air into water. Which path most accurately shows the refraction?
A. A
B. B
C. C
D. D
E. E
40. A ray of light in plastic reaches the edge of the plastic. The medium surrounding the plastic is air and the
angle of incidence is larger than the critical angle. What will happen?
A. The ray will refract out of the plastic, bending away from the normal line.
B. The ray will refract out of the plastic, bending toward the normal line.
C. The ray will experience total internal reflection, the angle of reflection being smaller than the angle of
incidence.
D. The ray will experience total internal reflection, the angle of reflection equaling the angle of incidence.
E. The ray will experience total internal reflection, the angle of reflection being larger than the angle of
incidence.
physics 100 prac exam#4 Key
1. A
2. B
3. D
4. E
5. B
6. A
7. A
8. C
9. E
10. E
11. A
12. A
13. B
14. D
15. B
16. C
17. C
18. A
19. B
20. C
21. A
22. C
23. E
24. A
25. B
26. C
27. B
28. C
29. D
30. B
31. C
32. A
33. B
34. D
35. B
36. D
37. A
38. B
39. C
40. D
physics 100 prac exam#4 Summary
Category
Griffith - Chapter 14
Griffith - Chapter 15
Griffith - Chapter 16
Griffith - Chapter 17
# of Question
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