Transcript R - SCHOOLinSITES

Cutnell/Johnson
Physics 8th edition
Classroom Response System Questions
Chapter 18 Electric Forces and Electric Fields
Reading Quiz Questions
18.1.1. Which one of the following values is the smallest possible
amount of free charge that has been discovered?
a) 5.34  1020 coulombs
b) 1.60  1019 coulombs
c) 1.38  1023 coulombs
d) 6.63  1034 coulombs
e) 8.85  1012 coulombs
18.1.2. Which one of the following statements concerning the net
electric charge on an object is true?
a) An object with a net negative charge has an excess number of
protons.
b) The net charge can have any value greater than 1.60  1019
coulombs.
c) The net charge on an object is always a negative number.
d) Since protons are larger, a proton can carry more charge than an
electron.
e) The net charge is quantized.
18.1.3 Which one of the following statements concerning atoms is
false?
a) Electrical charges are uniformly distributed throughout the volume
occupied by an atom.
b) The nucleus of an atom has a positive net electrical charge.
c) Neutrons do not have an electrical charge.
d) Electrons within atoms do not follow discrete paths or orbits.
e) Atoms can lose electrons.
18.2.1. Complete the following sentence: When animal fur is rubbed
along an ebonite rubber rod,
a) The rubber becomes positively charged and the fur becomes
negatively charged.
b) The rubber and the fur become positively charged.
c) The rubber becomes negatively charged and the fur becomes
positively charged.
d) The rubber and the fur become negatively charged.
e) The rubber becomes negatively charged and the fur remains
electrically neutral.
18.2.2. Which one of the following rules, laws, or principles describes
how the net electric charge of an isolated system undergoing any
process remains constant?
a) Coulomb’s principle
b) rule of seventy-two
c) principle of electric induction
d) law of conservation of electric charge
e) law of triboelectric synthesis
18.2.3. Which one of the following statements concerning the electric
force is true?
a) Two charged objects with identical charges will exert an attractive
force on one another.
b) It is possible for a small negatively-charged particle to float above
a negatively charged surface.
c) A positively-charged object is attracted toward another positivelycharged object.
d) The electric force cannot alter the motion of an object.
e) Newton’s third law of motion does not apply to the electrostatic
force.
18.2.4. A charged particle, labeled A, is located at the midpoint between two other
charged particles, labeled B and C, as shown. The sign of the charges on all
three particles is the same. When particle A is released, it starts drifting toward
B. What can be determined from this behavior?
a) The charge on A is larger than the charge on B.
b) The charge on A is larger than the charge on C.
c) The charge on C is larger than the charge on B.
d) The charge on B is larger than the charge on A.
e) The charge on B is larger than the charge on C.
18.2.5. Which one of the following statements is a consequence of charge
being conserved?
a) The difference between the number of positive and negative charges
does not change for a given system.
b) If you examine a system at different times, the total number of charges
will change.
c) Energy within the system is also conserved.
d) The positive and negative charges within a system must be quantized.
e) The numbers of electrons and protons for a given system cannot
change.
18.3.1. Complete the following sentence: an electric insulator has
a) the ability to easily conduct electricity, but does not easily conduct
heat.
b) few electrons available to conduct electricity.
c) the ability to easily conduct electricity and heat.
d) no ability to conduct electricity.
e) many free electrons available to conduct electricity.
18.3.2. Which one of the following statements concerning electrical
conductors is false?
a) Rubber is an excellent electrical conductor.
b) A material that is a good electrical conductor has many free
electrons that can easily move around inside the material.
c) When a positively-charged object is moved into contact with an
electrical conductor, electrons move toward the object.
d) Materials that are good thermal conductors are often good
electrical conductors.
e) Most metals are very good electrical conductors.
18.3.3. Which of the following terms is used to describe a
material that does not allow electrons to easily move
through it?
a) conductor
b) resistor
c) transformer
d) insulator
e) inductor
18.4.1. Which of the following statements describes an object being charged
by induction?
a) A glass rod is rubbed with silk.
b) A negatively-charged object is brought into contact with an initially
uncharged conductor. When they are separated, both objects are
negatively charged.
c) A rubber rod is rubbed with animal fur.
d) A positively-charged object is brought near with an initially uncharged
insulator. The surface of the insulator becomes slightly negatively
charged.
e) As you grab a door knob in the winter time, you feel a slight electric
spark.
18.4.2. A conductor that is initially electrically neutral is touched
by a rod that has a net positive charge. Which of the
following statements describing the conductor after the rod is
removed is true?
a) The conductor will have a net positive charge.
b) The conductor will electrically neutral.
c) The conductor will have a net negative charge.
18.5.1. Two positively charged particles are separated by a distance r.
The force on particle 1 is F due to particle 2. The force on particle
2 is 2F due to particle 1. Is the previous sentence true or false?
Explain why this is the case.
a) The sentence is true, if the net charge of particle 1 is twice that of
particle 2.
b) The sentence is false because the forces on each of the two objects
are equal in magnitude, but opposite in direction.
c) The sentence is true since the particles are separated by a distance r.
d) The sentence is false because two positively charged particles
cannot exert a force on each other.
18.5.2. Two positively charged particles are separated by a distance r.
Which of the following statements concerning the electrostatic
force between acting on each particle due to the presence of the
other is true?
a) The electrostatic force may be calculated using Faraday’s law.
b) The electrostatic force depends on the masses of the two particles.
c) The electrostatic force depends on r2.
d) The electrostatic force increases as r is increased.
e) The electrostatic force is on each particle is directed toward the
other particle.
18.5.3. Coulomb’s law is similar to Newton’s law of gravitation in several
ways. Which one of the statements is not a similarity between these two
laws?
a) In both laws, the force is inversely proportional to the square of the
distance between two particles.
b) In both laws, the force decreases with increasing distance between the
two particles.
c) In both laws, the force is proportional to the product of an intrinsic
property of each of the two particles.
d) In both laws, the force is always one of attraction between the two
particles.
e) In both laws, there is a proportionality constant that appears.
18.6.1. An electron is a negatively charged particle that has a charge of
magnitude, e = 1.60  1019 C. Which one of the following statements best
describes the electric field at a distance r from the electron?
a) The electric field is directed toward the electron and has a magnitude of ke/r2.
b) The electric field is directed away from the electron and has a magnitude of
ke/r2.
c) The electric field is directed toward the electron and has a magnitude of ke/r.
d) The electric field is directed away from the electron and has a magnitude of
ke/r.
e) The electric field is directed toward the electron and has a magnitude of ke2/r.
18.6.2. Which of the following statements concerning the electric field is
false?
a) The SI unit of the electric field is the newton per meter (N/m)
b) The electric field is a vector quantity.
c) At a given point, a charged particle will experience a force, if an
electric field is present at that location.
d) If a positively-charged particle is placed at a location where the
electric field is directed due north, it will be accelerated due north.
e) The magnitude of the electric field at a particular location due to a
particular charged particle is inversely proportional to the distance of
the particle from that location.
18.6.3. Which of the following combination of units are those for the
strength of the electric field?
2
kg

m
a)
C  s2
b) N  m
C
c)
kg  m
Cs
d)
N
C
e)
Cm
s
18.6.4. The direction of the electric field is the same as which of the
following properties related to a test charge?
a) velocity of the test charge
b) force on a positive test charge
c) acceleration of a negative test charge
d) displacement of a moving test charge
e) None of the above choices are related to the direction of the electric
field.
18.7.1. Which of the following statements concerning electric field lines
is false?
a) Electric field lines between two charged particles are often curved.
b) Electric field lines are a method proposed by Michael Faraday to map
the electric field at various locations.
c) Electric field lines can be used to indicate the local magnitude of the
electric field.
d) Electric field lines are always directed radially away from a
positively-charged particle.
e) An electric field line indicates the direction of the force on an electron
placed on the line.
18.7.2. Consider the following observations: (1) electric field lines are
drawn connecting two point charges labeled A and B, (2) charge A
is due north of charge B, and (3) a proton placed at the mid-point
on a line connecting the two point charges travels due south.
Which one of the following statements correctly indicates the signs
of the two charges?
a) Charge A is positive and charge B is negative.
b) Charge A is positive and charge B is positive.
c) Charge A is negative and charge B is positive.
d) Charge A is negative and charge B is negative.
18.7.3. Which one of the following statements concerning parallel
plate capacitors is false?
a) The plates are made from metal.
b) One of the plates has a net positive charge and one has a net
negative charge.
c) The electric field is proportional to the charge per unit area.
d) Electric field lines are directed from the negative plate to the
positive plate.
e) The electric field lines between the plates are parallel and evenly
spaced.
18.7.4. Complete the following statement: Electric field lines
depend on
a) the direction of the electric field.
b) the strength of the electric field.
c) the force exerted on a test charge.
d) All of the above choices correctly complete the statement.
e) None of the choices correctly complete the statement.
18.7.5. Consider the field lines shown in the drawing. Which one of the following
statements concerning this situation is true?
a) These field lines are those for a
positively charged particle.
b) These field lines are those for a
negatively charged particle.
c) These field lines are those for a
positively charged particle and a
negatively charged particle.
d) These field lines are those for two
positively charged particles.
e) These field lines are those for two negatively charged particles.
18.7.6. Consider the field lines shown in the drawing. Which one of
the following statements concerning this situation is true?
a) A is a positively charged particle
and B is negatively charged.
b) B is a positively charged particle
and A is negatively charged.
c) A and B are both positively
charged.
d) A and B are both negatively
charged.
18.9.1. Which of the following laws, principles, or definitions
describes the electric flux through a surface that encloses a charge?
a) Amonton’s law
b) Gauss’ law
c) Carnot’s principle
d) definition of a fluxon
e) electric flux principle
18.9.2. A conducting sphere (shown in grey in the drawing) of radius R has a
number q of excess electrons distributed uniformly over its surface. A
spherically-shaped Gaussian surface with a radius r < R is represented in
the drawing by the dashed circle. Applying Gauss’ law, what is the
magnitude of the electric field inside the Gaussian sphere?
q
a) 4 r
0
q
b)
4 0r 2
c) zero N/C
d)
q
r
4 0r 2
e)
q
18.9.3. To what does Gauss’ law relate the electric field at points
on a Gaussian surface?
a) charges near the surface
b) electric field flux leaving the volume enclosed by the surface
c) electric field flux entering the volume enclosed by the surface
d) net charge enclosed by the surface
e) velocity of charges entering or leaving the surface
18.10.1. Which of the following properties makes selenium a useful
material in photocopiers?
a) Selenium is opaque and is a good toner material.
b) Selenium is a photoconductor.
c) Selenium always has a net positive charge.
d) Selenium is an electrical insulator when exposed to light.
e) Selenium has a large thermal conductivity making it better suited
for the high temperature of the toner.
18.10.2. Which of the following statements best represents the purpose
of the deflection plates within an inkjet printer?
a) The plates control the direction of ink droplets within the printer.
They are turned on to prevent the ink from striking the paper.
b) The plates control the direction of electrons within the printer.
c) The plates control the charging of ink droplets. They are turned on
to charge the ink droplets.