Extra Conceptual Questions Chapter 15

False

Electric field lines radiate from a negative charge to a positive charge. Select one: True False

e. Neither: both negative and positive charge are present simultaneously in all solid materials on Earth and the process described involves a transfer of charge, not the creation of charge.

Enrico says that positive charge is created when you rub a glass rod with silk, and that negative charge is simply the absence of positive charge. Rosetta says that negative charge is created and that positive charge is the absence of positive charge. (She has heard that Ben Franklin should have reversed the signs he associated with the charges.) Which one, if either, is correct? Select one: a. Enrico, because there really is only one kind of charge. b. Rosetta, because there really is only one kind of charge. c. Neither: although no charge is present originally, both types of charge are created through friction. d. Both: only one type of charge is created by friction at any one time. e. Neither: both negative and positive charge are present simultaneously in all solid materials on Earth and the process described involves a transfer of charge, not the creation of charge.

b. FAB = - FBA

Object A has a charge of + 2 C, and object B has a charge of +6µC. Which statement is true about the electric force on the objects? Select one: a. FAB = - 3FBA b. FAB = - FBA c. 3FAB = - FBA d. FAB = FBA e. 3FAB = FBA

c. C

Object A has a charge q on it, object B has a charge q on it, and object C has a charge 2q on it. These charges are arranged, one each, at the vertices of an equilateral triangle. Which charge has the greatest magnitude electric force on it? Select one: a. A b. B c. C d. All have equal magnitude forces on them.

a. the shape of the conductor

Relative distribution of charge density on the surface of a conducting solid depends on: Select one: a. the shape of the conductor. b. mass density of the conductor. c. type of metal of which the conductor is made. d. strength of the earth's gravitational field.

c. remain the same

A spherical balloon contains a positively charged object as its center. As the balloon is inflated to a greater volume while the charged object remains at the center, the electric FLUX at the surface of the balloon will.... Select one: a. increase. b. decrease. c. remain the same.

c. The flux increases and the electric field decreases

A spherical surface surrounds a point charge in its center. If the charge is doubled and if the radius of the surface is also doubled, what happens to the electric flux out of the surface and the magnitude of the electric field at the surface as a result of these doublings? Select one: a. Both the flux and the electric field remain the same. b. The flux increases and the electric field remains the same. c. The flux increases and electric field decreases. d. Both the flux and the electric field increase. e. Both the flux and the electric field decrease.

a. is unaffected

A test charge of +3 µC is at a point P where an external electric field is directed to the right and has a magnitude of 4.0x106 N/C. If the test charge is replaced with another test charge of -3 µC, the external electric field at P Select one: a. is unaffected. b. reverses direction. c. changes in a way that cannot be determined.

c. A rubber rod and a glass rod charged this way have opposite charges on them

Rubber rods charged by rubbing with cat fur repel each other. Glass rods charged by rubbing with silk repel each other. A rubber rod and a glass rod charged respectively as above attract each other. A possible explanation is that Select one: a. Any two rubber rods charged this way have opposite charges on them. b. Any two glass rods charged this way have opposite charges on them. c. A rubber rod and a glass rod charged this way have opposite charges on them. d. All rubber rods always have an excess of positive charge on them. e. All glass rods always have an excess of negative charge on them.

a. Distributed uniformly on the outside surface of the sphere

Suppose that you touch an isolated metal (conducting) sphere with a negatively charged rod then remove the rod. Where will the extra electrons be located on the metal sphere? Select one: a. Distributed uniformly on the outside surface of the sphere. b. At the center of the sphere. c. Isolated in a small bunch near where the rod touched the sphere. d. Located in a small bunch somewhere on the sphere's surface. e. Nonsense. It is not possible for there to be extra electrons on the sphere.

False

Although charges can create a force, they cannot cause another charge to accelerate. Select one: True False

a. The electrons move closer to the top plate

An electron is passed through a constant electric field between two plates. The top plate has a negative charge and the bottom plate has a positive charge. The initial velocity of the electron is 3.0x106 m/s. Which one of the following is NOT a possible outcome from the electron passing through this field? Select one: a. The electron moves closer to the top plate. b. The electron moves closer to the bottom plate. c. The electron accelerates. d. The electron's final velocity is 2x the initial velocity.

b. positive

An uncharged conductor is supported by an insulating stand. I pass a positively charged rod near the left end of the conductor, but do not touch it. The right end of the conductor will be: Select one: a. negative. b. positive. c. neutral. d. attracted.

d. where curvature is greatest

At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid? Select one: a. where surface curves inward b. where surface is flat c. where curvature is least d. where curvature is greatest

b. Electrons are added to the rod

Susan rubs a piece of fur on a hard rubber rod, giving the rod a negative charge. What happens? Select one: a. Protons are removed from the rod. b. Electrons are added to the rod. c. The fur is also charged negatively. d. The fur is left neutral.

d. electrical charges on deflecting plates

The beam of electrons that hits the screen of an oscilloscope is moved up and down by: Select one: a. gravity. b. a phosphorescent coating. c. varying the electron's charge. d. electrical charges on deflecting plates.

b. dipole

The combination of two separated point charges of opposite sign but equal magnitude is called an electric: Select one: a. monopole. b. dipole. c. quadrapole. d. magnapole.

d. The sphere's outer surface

The electric field associated with a uniformly charged hollow metallic sphere is the greatest at: Select one: a. the center of the sphere. b. the sphere's inner surface. c. infinity. d. the sphere's outer surface.

b. perpendicular and into the surface

The electric field at the surface of a negatively charged conductor has a direction characterized by being ________ . Select one: a. tangent to the surface. b. perpendicular and into the surface. c. perpendicular and out of the surface. d. at a forty-five degree angle to the surface.

d. perpendicular outward and away from the charge

The electric field at the surface of a positively charged conductor has a direction characterized by which of the following? Select one: a. tangent to the surface b. perpendicular inward toward the charge c. at a 45° angle to the surface d. perpendicular outward and away from the charge

c. R^2

The electric field of a point charge has an inverse ________ behavior. Select one: a. r1/2 b. r c. r2 d. r3

True

The greater the amount of charge, the greater the number of electric field lines. Select one: True False

c. the field strength

The number of electric field lines passing through a unit cross sectional area is indicative of Select one: a. the field direction b. the charge density c. the field strength d. a charge in motion

d. Force, distance, and electric charge

The symbol mc069-1.jpg appears in Coulomb's law because we use independently defined units for Select one: a. force and distance. b. charge and distance. c. distance and force. d. force, distance and electric charge. e. charge.

c. x= 5m

Three equal positive charges are placed on the x-axis, one at the origin, one at x = 2 m, and the third at x = 4 m. Of the following points, which has the greatest magnitude electric field? Select one: a. x = 1 m b. x = 3 m c. x = 5 m d. The electric field has the same magnitude at all three positions.

c. -Q/4

Two equal charges, each Q, are separated by some distance. What third charge would need to be placed half way between the two charges so that the net force on each charge would be zero? Select one: a. -Q b. -Q/2 c. -Q/4 d. -Q/8

a. the two charges have the same sign

Two point charges of unknown magnitude and sign are a distance d apart. The electric field is zero at one point between them, on the line joining them. What can you conclude about the charges? Select one: a. The two charges have the same sign. b. The charges have an equal value. c. The two charges have opposite signs. d. This cannot happen with only two charges.

a. On object is positively charged and the other is negatively charged.

Two small objects are suspended from threads. When the objects are moved close together, they attract one another. What of the following could produce this result? Select one: a. On object is positively charged and the other is negatively charged. b. One object is positively charged and the other conductor is uncharged. c. One object is negatively charged and the other conductor is uncharged. d. All of the above could result in an attraction.

a. the clothes rub against each other

What is the origin of "static cling"? This a phenomenon that sometimes affects clothing in the dryer. Select one: a. The clothes rub against each other. b. Electricity is sent through the metal tumbler to the clothing. c. The removal of the water from the clothes causes them to be more conductive to charge. d. The clothes are not charged, the person touching them is.

a. Electrons are removed from the rod.

When a glass rod is rubbed with silk, which of the following statements best describes what happens? Select one: a. Electrons are removed from the rod. b. Protons are removed from the silk. c. The silk is charged positively. d. The silk remains neutral.

e. in a direction determined by the vector sum of the electric fields of Q1 and Q2.

When a positive charge q is placed in the field created by two other charges Q1 and Q2, each a distance r away from q, the acceleration of q is Select one: a. in the direction of the charge Q1 or Q2 of smaller magnitude. b. in the direction of the charge Q1 or Q2 of greater magnitude. c. in the direction of the negative charge if Q1 and Q2 are of opposite sign. d. in the direction of the positive charge if Q1 and Q2 are of opposite sign. e. in a direction determined by the vector sum of the electric fields of Q1 and Q2.

d. tangents to the directions in which either static or moving charges would accelerate when passing through points on those lines.

When gravitational, magnetic and any forces other than static electric forces are not present, electric field lines in the space surrounding a charge distribution show Select one: a. the directions of the forces that exist in space at all times. b. only the directions in which static charges would accelerate when at points on those lines c. only the directions in which moving charges would accelerate when at points on those lines. d. tangents to the directions in which either static or moving charges would accelerate when passing through points on those lines. e. the paths static or moving charges would take.

c. voltage

Which is not a force? Select one: a. gravity b. electric c. voltage d. friction

a. if the charge is moved outside of the surface

Which of the following WILL change the flux through the closed surface? A point charge is placed at the center of a spherical Gaussian surface. The flux will change ... (select the correct answer) Select one: a. if the charge is moved outside of the surface. b. if the surface is morphed into a cube of the same volume. c. if the sphere is morphed into a cube of half the volume. d. if a new charge is placed near the sphere, but just outside. e. if the charge is moved off center, but still within the sphere.

a. charges on the surface dont move

Which of the following best characterizes electrical insulators? Select one: a. charges on the surface don't move b. high tensile strength c. electric charges move freely d. good heat conductors

d. all of the above choices are valid

Which of the following characteristics are held in common by both gravitational and electrostatic forces when dealing with either point masses or charges? Select one: a. inverse square distance law applies b. forces are conservative c. potential energy is a function of distance of separation d. all of the above choices are valid

a. the rate of nutrients moving through a cell wall divided by the surface area of the cell

Which of the following is a type of flux? Select one: a. The rate of nutrients moving through a cell wall divided by the surface area of the cell. b. The amount of force it takes to push a car up a hill. c. The speed of the water in the Mississippi river. d. The velocity of the electric field

c. Milikan

Who was the first to determine the electron's charge? Select one: a. Franklin b. Coulomb c. Millikan d. Faraday

b. 4/3

A charge Q accumulates on the hollow metallic dome, of radius R, of a Van de Graaff generator. A probe measures the electric field strength at various points outside the sphere surface. By what factor will the electric field value at the 2R distance be changed if the charge value were increased to (4/3)Q? Select one: a. (4/3)2 b. 4/3 c. 3/4 d. (3/4)2

d. (3/4)2

A charge Q accumulates on the hollow metallic dome, of radius R, of a Van de Graaff generator. A probe measures the electric field strength at various points outside the sphere surface. If the probe is initially at a distance 3R from the sphere's center and then is moved to 4R, by what factor will the electric field reading change? Select one: a. (4/3)2 b. 4/3 c. 3/4 d. (3/4)2

c. stays the same

A charge, +Q, is placed inside a balloon and the balloon is inflated. As the radius of the balloon r increases the number of field lines going through the surface of the balloon: Select one: a. increases proportional to r2. b. increases proportional to r. c. stays the same. d. decreases as 1/r.

b. anti-parallel

A free electron is in an electric field. With respect to the field, it experiences a force acting: Select one: a. parallel. b. anti-parallel (opposite in direction). c. perpendicular. d. along a constant potential line.

a. the net electric flux will be zero

A gaussian surface encloses an electric dipole (such as NaCl) Which of the following is true about the electric flux through this surface? Select one: a. The net electric flux will be zero. b. We cannot make any conclusions, there is not enough information. c. The net flux would be into the surface since it contains a negative charge. d. The net flux would be out of the surface since it contains a positive charge.

a. lower

A metal sphere is initially uncharged. After being touched by a charged rod, the metal sphere is positively charged. The mass of the sphere is now ___________. Select one: a. lower. b. higher. c. the same.

True

A negative charge will tend to accelerate in the opposite direction of the electric field. (An electron's acceleration vector points in the opposite direction of the electric field.) Select one: True False

True

A particular gaussian surface contains no net charge. The net flux through this surface is zero. Select one: True False

False

An object classified as an insulator can never have a charge. Select one: True False

b. B and C

Charge A has 10 electric field lines coming out, Charge B has 20 lines coming out, and Charge C has 30 lines coming in. Which pair of these charges will have the largest force between them if placed one cm apart? Select one: a. A and B b. B and C c. C and A d. More information is needed.

b. X=3 m

Charges q, q, and -q are placed on the x-axis at x = 0, x = 2 m, and x = 4 m, respectively. At which of the following points does the electric field have the greatest magnitude? Select one: a. x = 1 m b. x = 3 m c. x = 5 m d. The electric field has the same magnitude at all these positions.

False

For a conductive material, in electrostatic equilibrium, the charge is distributed equally throughout the volume material rather than being at the surface alone. Select one: True False

a. the amount of charge contained within the surface

Gauss's Law tells us that the net amount of flux through a closed surface is proportional to ... (select the correct answer) Select one: a. the amount of charge contained within the surface. b. the average radius of the surface. c. the number of verticies on the surface. d. the amount of charge surrounding the surface. e. the angle the electric field makes with the surface.

c. The charges in the uncharged object can become polarized.

How can a charged object attract an uncharged object made of non-conducting material? Select one: a. The uncharged object must somehow gain a like charge. b. The uncharged object must somehow gain an unlike charge. c. The charges in the uncharged object can become polarized. d. Attraction of an insulator is not possible.

b. the electric field inside the conductor must be zero

If a conductor is in electrostatic equilibrium near an electrical charge: Select one: a. the total charge on the conductor must be zero. b. the electric field inside the conductor must be zero. c. any charges on the conductor must be uniformly distributed. d. the sum of all forces between the conductor and the charge must be zero.

False

If a spherical gaussian surface is drawn around the outside of a charged metal ball, the net flux through the gaussian surface will be zero. Select one: True False

b. must be negative

If body M, with a positive charge, is used to charge body N by induction, what will be the nature of the charge left on the latter? Select one: a. must be equal in magnitude to that on M b. must be negative c. must be positive d. must be greater in magnitude than that on M

c. must be positive

If body P, with a positive charge, is placed in contact with body Q (initially uncharged), what will be the nature of the charge left on Q? Select one: a. must be equal in magnitude to that on P b. must be negative c. must be positive d. must be greater in magnitude than that on P

d. 1/9

If the distance between two point charges is tripled, the mutual force between them will be changed by what factor? Select one: a. 9.0 b. 3.0 c. 1/3 d. 1/9

a. 9.0

If the size of the charge value is tripled for both of two point charges maintained at a constant separation, the mutual force between them will be changed by what factor? Select one: a. 9.0 b. 3.0 c. 1/3 d. 1/9

b. leave both plats and go to infinity

If two parallel, conducting plates have equal positive charge, the electric field lines will: Select one: a. leave one plate and go straight to the other plate. b. leave both plates and go to infinity. c. enter both plates from infinity. d. none of the above.

True

The electric field for a negative charge points radially into the charge. Select one: True False

d. 4

Two point charges are 4 cm apart. They are moved to a new separation of 2 cm. By what factor does the resulting mutual force between them change? Select one: a. 1/2 b. 2 c. 1/4 d. 4

b. the outside surface of the conductor will become positively charged

b. the outside surface of the conductor will become positively charged.