True/False
Indicate whether the sentence or statement is true
or false.
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| 1. | The
electric force between two point charges is directly proportional to the product of the charges and
inversely proportional to the square of the distance between them.
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| 2. | If
the sum of all the electric forces on a charge is zero, the charge must be at rest.
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| 3. | Electric charges always move along a path given by electric field lines.
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| 4. | If
the electric field in a region of space is zero, the electric force on any single charge placed in
that region is also zero.
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| 5. | When
a small positive test charge is moved toward another positive charge, the test charge experiences an
increasing electric force, an increasing electric field, and an increase in electric potential
energy. Further, the charge finds itself moving into a region of higher electric
potential.
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| 6. | Negative charges move from regions of high electric potential to regions of lower
electric potential.
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| 7. | An
oil droplet in a Millikan apparatus with uncharged plates falls at a constant speed because it has a
charge.
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| 8. | The
laws of conservation of momentum and conservation of mechanical energy determine the motion of
interacting charged particles.
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| 9. | A
negatively charged object that is fired directly away from a positively charged object will cause the
kinetic energy to increase and the potential energy to decrease.
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| 10. | Magnetic field lines never cross.
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| 11. | Uniform electric, gravitational, and magnetic fields can change the speeds of
particles that are initially moving perpendicular to the fields.
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| 12. | A
charged particle moving parallel to an electric, gravitational, or magnetic field experiences a
force.
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| 13. | Charges moving perpendicular to a uniform magnetic field experience circular motion
because the magnetic force is always perpendicular to the velocity of the charge.
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| 14. | Two
long, parallel, straight wires repel each other if their currents are in the same
direction.
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Multiple Choice
Identify the
letter of the choice that best completes the statement or answers the question.
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| 15. | The force on
a small, uniform conducting sphere of charge q1 a distance d from another
sphere of charge q2 is +F. If the sphere of charge q1 is
touched with an identical neutral conducting sphere, which is moved far away and then placed a
distance  from q2, the force on the sphere
is a. | +F | b. | +2F | c. | | d. | | e. | none of these | | |
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| 16. | Three
identical charges are placed on a line from left to right, with adjacent charges separated by a
distance d. The magnitude of the force on a charge from its nearest neighbour is F. The
net force on each charge, from left to right, is a. | +2F, +2F, +2F | b. |  ,
0,  | c. | +2F, 0, +2F | d. | F, 0,
F | e. | none of these | | |
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| 17. | An electron
experiences a force of 1.6  10-16 N [left] from an electric field. The electric
field is a. | 1.6 
103 N/C | b. | 1.0  103 N/C
[left] | c. | 1.0  103 N/C
[right] | d. | 1.0 N [right] | e. | none of
these | | |
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| 18. | As the
distance between two charges increases, the electric potential energy of the two-charge
system a. | always
increases | b. | always decreases | c. | increases if the
charges have the same sign, decreases if they have opposite signs | d. | increases if the
charges have opposite signs, decreases if they have the same sign | e. | is always
negative | | |
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| 19. | Two
oppositely charged parallel plates are separated by 12 mm. The uniform electric field between the
plates has a magnitude of 3.0  103 N/C. An
electron is ejected from the negative plate, with an initial velocity of zero. The kinetic energy of
the electron when it has moved halfway to the positive plate is a. | 2.9 
10-18
J | b. | 5.8 
10-18
J | c. | 1.4 
10-18
J | d. | 0
J | e. | none of
these | | |
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| 20. | A positive
charge of mass 2m is initially at rest, directly to the left of a negative charge of mass
m, moving rightward with speed v. When the negative charge has velocity 
[right], the velocity of the positive charge is a. | 0 | b. | 
[right] | c. | 
[left] | d. | 
[right] | e. | 
[left] | | |
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| 21. | Which of the
following statements is true about any type of field line: a. | They never
cross. | b. | They are always perpendicular to the surface of the object producing
the field. | c. | They point in the direction of motion. | d. | They signify a force,
experienced by a test particle of positive charge q, whose magnitude equals the product of
q and the field magnitude. | e. | They never form closed loops. | | |
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| 22. | Through a
narrow hole you view an apparatus in which a small charged sphere, attached to a thin thread, hangs
at rest at an angle of 10° to the right of the vertical when there is no wind. From your
observation, you can infer that a. | the electric field points right | b. | the electric field
points left | c. | the electric field is zero | d. | the net force on the
sphere is zero | e. | the tension in the thread is smaller than the gravitational force on
the sphere | | |
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| 23. | An electron
moves within a uniform magnetic field of 0.20 T, at a speed of 5.0 
105 m/s. The magnetic force on the electron a. | is 1.6 
10-14
N | b. | is 1.6 
10-14 N
[perpendicular to velocity] | c. | is 1.6  10-14 N
[perpendicular to magnetic field] | d. | is zero | e. | cannot be determined from the information | | |
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| 24. | If a
straight length of wire with a current is immersed in a uniform magnetic field, then the
wire a. | experiences no force if
it is perpendicular to the field | b. | experiences some magnetic force, no matter what its orientation in the
field | c. | experiences no force if it is parallel to the
field | d. | experiences no force if the current is
alternating | e. | does not satisfy any of the above
descriptions | | |
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| 25. | An
electron passes into a magnetic field at 90°. Its consequent circular path has radius r. If the
speed of the electron were twice as great and the magnetic field were twice as strong, the radius
would be
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| 26. | Particles in
a mass spectrograph emerge from a velocity selector into a uniform magnetic field at 90°. If the
radius of the circular path of particle 1 is larger than the radius for particle 2,
then a. | particle 1 is of
greater mass than particle 2 | b. | particle 1 has a smaller charge than particle
2 | c. | the charge-to-mass
ratio of particle 1 is smaller than the charge-to-mass ratio of particle 2 | d. | the charge-to-mass
ratio of particle 1 is larger than the charge-to-mass ratio of particle 2 | e. | particle 1 is moving
faster than particle 2 | | |
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Completion
Complete each sentence or
statement.
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| | 27. | A(n)
_______ exists in a region of space when an appropriate object experiences a force in that
region.
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| | 28. | The
gravitational and electric forces are governed by a(n) _______ law with respect to the distance
between the objects.
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| | 29. | If a charged
particle passes into a(n) _______ field perpendicular to the field lines, the speed does not
change.
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| | 30. | Electric
field lines are always _______ to a conductor in static equilibrium.
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| | 31. | A(n)
_______ cable is shielded from both electric and magnetic fields.
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| | 32. | The area
under the curve on an electric force-displacement graph represents the change in _______
.
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| | 33. | To analyze
the motion of an elastic collision between two charged particles we use conservation of _______
and _______ .
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| | 34. | When a
charged particle of mass m passes into either a uniform gravitational field or an electric
field perpendicular to the field lines, it follows a(n) _______ path; however if it passes into
a magnetic field it follows a(n) _______ path.
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| | 35. | When
separating two charges of mass m the gravitational and electric force _______ , the
gravitational potential energy _______ , and the electric potential energy _______ .
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