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• Cutnell/Johnson Physics 8th editionClassroom Response System Questions

Chapter 18 Electric Forces and Electric FieldsReading 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 1020 coulombs

b) 1.60 1019 coulombs

c) 1.38 1023 coulombs

d) 6.63 1034 coulombs

e) 8.85 1012 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 1019 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) Coulombs 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 positively-charged object.

d) The electric force cannot alter the motion of an object.

e) Newtons 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 Faradays 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. Coulombs law is similar to Newtons 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 1019 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?

a)

b)

c)

d)

e)

• 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 i