Download Forces and Fields Review

Forces and Fields Review
Use the following information to answer the next question.
A student places a positively charged sphere near a metal rod. Both are on insulated
stands and the rod is grounded.
1.
The distribution of charge on the rod is
A. positive at end X and electrons move off the rod into the ground
B. negative at end X and electrons move off the rod into the ground
C. positive at end X and electrons move onto the rod from the ground
D. negative at end X and electrons move onto the rod from the ground
Use the following information to answer the next question.
Electrostatic Forces
A soap bubble rests on a loop of copper wire. After the wire is touched with negatively
charged rod S, the bubble is freed and suspended electrostatically above rod T.
2.
The bubble is suspended because
A.
B.
C.
D.
rod T is positively charged and repels the positive charges on the bubble
the bubble induces a positive charge on rod T and is held up by repulsion
rod T is negatively charged and repels the negative charges on the bubble
the bubble induces a negative charge on rod T and is held up by repulsion
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3.
A conducting sphere X that has an initial charge of 2.0 ×10–8 C and an identical
conducting sphere Y that has an initial charge of –3.0 × 10–8 C are touched together. After
they are separated, the charge on sphere X is
A.
B.
C.
D.
–5.0 × 10–9 C
–1.0 × 10–8 C
–2.5 × 10–8 C
–5.0 × 10–8 C
Use the following information to answer the next question.
Two identically charged objects are placed near a point, P, as shown below.
4.
Which of the following free-body diagrams, drawn to scale, illustrates the electrostatic
forces acting on a positive test charge placed at point P?
A.
B.
C.
D.
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Use the following information to answer the next three questions.
A student has three identical spheres, K, L, and M, on insulated stands
equally spaced in a line as shown below. The charges on the spheres are qK
= +3x, qL = − 5x, and qM = +2x.
5.
The direction of the net electric force on sphere L due to spheres K and M is
A.
B.
C.
D.
6.
to the left of the page
to the right of the page
toward the top of the page
toward the bottom of the page
At point P, above sphere L, the direction of the net electric field is mostly
A.
B.
C.
D.
to the left of the page
to the right of the page
toward the top of the page
toward the bottom of the page
Use the following additional information to answer the next question.
The spheres are touched together and separated, without grounding, in
the following order.
Step I
Step II
Step III
Spheres K and L
Spheres K and M
Spheres L and M
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7.
Which of the following rows indicates the final charge present on each sphere?
Row
Sphere K
Sphere L
Sphere M
A.
0
0
0
B.
−x
−x
+2x
C.
D.
x
2
x
2
−x
x
4
x
2
x
4
Use the following information to answer the next question.
Charged spheres I, II and III are located as shown below.
8.
The net electrostatic force on sphere III that is caused by the charges on spheres I and II is
A.
B.
C.
D.
6.99 × 10−4 N, right
1.06 × 10−3 N, right
6.99 N, right
10.6 N, right
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Use the following information to answer the next two questions.
Three charges, q1, q2, and q3, are placed at the vertices of a right angle triangle, as
shown below.
9.
The magnitude of the net electrostatic force acting on q2 is
A.
B.
C.
D.
212 N
263 N
276 N
327 N
Numerical Response
10. The angle labelled θ indicates the direction of the net electrostatic force on q2. The value of
θ is __________°.
(Record your three-digit answer in the numerical-response section on the answer sheet.)
11.
The intensity and direction of the electric field produced by an alpha particle at a distance
of 5.0 10–11 m from the particle is
A.
B.
C.
D.
5.8 1011 N/C, toward the alpha particle
5.8 1011 N/C, away from the alpha particle
1.2 1012 N/C, toward the alpha particle
1.2 1012 N/C, away from the alpha particle
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Use the following information to answer the next question.
Electric Field Lines Near Two Charged Spheres
12.
The types of charge present on X and Y are, respectively,
A.
B.
C.
D.
negative and negative
negative and positive
positive and negative
positive and positive
Numerical Response
13. The electric field strength at a distance of 4.00 cm from a 1.20 × 10−5 C point charge,
expressed in scientific notation, is a.bc × 10d N/C. The values of a, b, c, and d are _____,
_____, _____, and _____.
(Record all four digits of your answer in the numerical-response section on the answer sheet)
14.
The magnitude of an electric field at a distance x from a point charge Q is 8.3 10–4 N/C.
Q
If the distance is increased to 3x and the charge is reduced to , then the magnitude of the
4
electric field will be
A.
B.
C.
D.
1.9 10–3 N/C
3.7 10–4 N/C
6.9 10–5 N/C
2.3 10–5 N/C
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Use the following information to answer the next question.
Four point charges are arranged as shown.
15.
The magnitude of the net electric field at point P due to these four point charges is
A.
B.
C.
D.
5.4 104 N/C
4.5 104 N/C
2.7 104 N/C
0.0 N/C
Use the following information to answer the next question.
Two point charges of equal magnitude, +Q and –Q, are each placed at an equal distance,
x, from point P, as shown below.
16.
The direction of the resultant electric field at point P is
A.
B.
C.
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D.
17.
When a charged particle accelerates (increases its speed) in an electric field, there is a
decrease in its
A.
B.
C.
D.
mass
charge
kinetic energy
potential energy
Use the following information to answer the next three questions.
Cathode-ray tubes (CRTs) are used for television and computer screens. They are set up
as shown below.
Electrons are “boiled off” the surface of the cathode and are accelerated toward the
anode. The cathode is 4.5 cm from the anode. A potential difference of 2.5 103 V
exists between the cathode and the anode. The electrons are deflected both side to side
and up and down by pairs of magnetic deflection coils mounted on the neck of the tube.
18. An electron hits the screen at a speed of
A.
B.
C.
D.
1.0 107 m/s
1.5 107 m/s
3.0 107 m/s
8.8 1014 m/s
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Use the following additional information to answer the next question.
An electron is travelling perpendicular to the magnetic deflection coils, into the page,
as shown below.
19. The coils that can produce a deflection toward the top of the screen are numbered
A.
B.
C.
D.
20.
1 and 3
2 and 4
1 and 2
3 and 4
An electron accelerates from rest across the gap between charged parallel plates and
reaches a final speed of v. If the potential difference across the plates is tripled, the final
speed of an electron accelerating from rest across the gap will be
A.
1
v
3
B.
1
v
3
C.
3v
D. 9 v
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Use the following information to answer the next question.
Magnetic Fields Around Two Bar Magnets
21.
Given the magnetic fields illustrated above, the magnets will repel in diagrams
A.
B.
C.
D.
I and II only
I and IV only
II and III only
II and IV only
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Use the following information to answer the next question.
Moving electrons can be deflected by electric fields, gravitational fields, and magnetic
fields. One electron is allowed to enter each type of field, as shown below.
● Represents field out of surface
×
22.
If the electron is deflected downward in each field, then field 1, field 2, and field 3 are,
respectively,
A.
B.
C.
D.
23.
Represents field into surface
electric, magnetic, and gravitational
gravitational, magnetic, and electric
magnetic, gravitational, and electric
magnetic, electric, and gravitational
Which of the following diagrams best illustrates the magnetic field near a wire that carries
an electron current out of the plane of the paper?
A.
B.
C.
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D.
24.
When two parallel conducting wires repel each other, the currents in the wires are
A.
B.
C.
D.
oppositely charged
oscillating in phase
in the same direction
in opposite directions
Use the following information to answer the next question.
Electrons can produce gravitational, electric, and magnetic fields as
a result of the following properties.
1
2
3
Charge
Mass
Speed
Numerical Response
25. Match electron properties as listed above with the field that they produce as given below.
You may use a number more than once. There is more than one correct answer.
Property: _________
Field: Gravitational
Field
_________ _________ and __________
Constant
Magnetic
Electric Field
Field
(Record all four digits of your answer in the numerical-response section on the answer sheet)
26.
The north pole of the solenoid shown to the right is at position
A.
B.
C.
D.
I
II
III
IV
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27.
The diagrams below show the direction of a magnetic field relative to a set of coordinate
axes. A negatively charged particle travels across the page in the positive x direction. The
magnetic configuration that will cause the particle to bend in the positive z direction is
A.
C.
B.
D.
Use the following information to answer the next question.
Cross-Section of a Wire Suspended in a Magnetic Field
A wire is placed between two permanent magnets. As shown in the diagram, it is
positioned so that it is perpendicular to the magnetic field and to the page. The
mass of the wire is 0.850 g. The length of the wire perpendicular in the magnetic
field is 1.30 cm.
Numerical Response
28. When a current of 1.00 A is passing through the wire, there is sufficient magnetic force to
keep the wire supported against gravity. The magnitude of the magnetic field, expressed in
scientific notation, is a.bc × 10−d T. The values of a, b, c, and d are _____, _____, _____,
and _____.
(Record all four digits of your answer in the numerical-response section on the answer sheet)
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Use the following information to answer the next two questions.
Earth’s Magnetic Field
The solar wind consists of particles emitted by the Sun. Some of these particles are
charged; therefore, when they enter Earth’s magnetic field, they experience a magnetic
force. A stream of charged particles travelling with a speed of 8.00 × 105 m/s
encounters Earth’s magnetic field, as shown below, at an altitude where the field has a
magnitude of 1.10 × 10–7 T.
29.
The protons in the solar wind experience a magnetic force
A.
B.
C.
D.
into the plane of the page
out of the plane of the page
in the direction the solar wind is travelling
opposite to the direction the solar wind is travelling
Numerical Response
30. Assume that the velocity of the solar wind particles is perpendicular to the magnetic field.
The radius of the circular path that protons in a solar wind follow, expressed in scientific
notation, is a.bc × 10d m. The values of a, b, c, and d are _____, _____, _____, and _____.
(Record all four digits of your answer in the numerical-response section on the answer sheet)
31.
A proton and an alpha particle have identical circular orbits in a magnetic field. The proton
has a speed of 4.4 105 m/s. The speed of the alpha particle is
A.
B.
C.
D.
1.1 105 m/s
2.2 105 m/s
4.4 105 m/s
8.8 105 m/s
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Use the following information to answer the next question.
The diagram below shows an experimental design used to investigate the effect of
a magnetic field on a vertical current-carrying conductor. The aluminum rod is able
to swing freely.
32.
When the switch is closed, a current in the circuit causes the bottom end of the aluminum
rod to swing
A.
B.
C.
D.
toward the retort stand
away from the retort stand
toward the south pole of the magnet
toward the north pole of the magnet
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Use the following information to answer the next question.
Almost all electric guitars use devices called electromagnetic pickups. A guitar
string is composed of metal that becomes magnetized by a permanent magnet
found below the string. A coil of wire surrounds the permanent magnet.
33.
When the string is plucked, a small current is produced in the coil of wire because
A.
B.
C.
D.
there is a charge buildup on the string
a potential difference is produced in the string
there is a current in the string that can be amplified
the string behaves as a magnet moving toward and away from the coil
Unit B: Forces and Fields – Answers
1.
D
13. 6747
25. 2113 or 2131
2.
C
14. D
26. A
3.
A
15. D
27. B
4.
C
16. C
28. 6411
5.
A
17. D
29. B
6.
D
18. C
30. 7594
7.
D
19. B
31. B
8.
C
20. C
32. B
9.
C
21. D
33. D
10. 78.0
22. A
11. D
23. D
12. A
24. D
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