PHYS 115 Exam 2 Ch 19,20,21

Gaussian surfaces A and B enclose the same positive point charge. The area of surface A is two times larger than that of surface B. How does the total electric flux through the two surfaces compare? a) The total electric flux through the two surfaces is equal. b) The total electric flux through surface B is four times larger than that through surface A. c) The total electric flux through surface A is eight times larger than that through surface B. d) The total electric flux through surface A is four times larger than that through surface B. e) The total electric flux through surface B is eight times larger than that through surface A.

A - the total electric flux is equal Remember that surface area cancels out in Gaussian surfaces

Which of the following statements are true? a) Heat is converted completely into work during isothermal expansion. b) Isothermal expansion is reversible under ideal conditions. c) During the process of isothermal expansion, the gas does more work than during an isobaric expansion (at constant pressure) between the same initial and final volumes.

A and B

There is a single electron at a distance from the point charge. On which of the following quantities does the force on the electron depend? Check all that apply. a- the distance between the positive charge and the electron b- the charge on the electron c- the mass of the electron d- the charge of the positive charge e- the mass of the positive charge f- the radius of the positive charge g - the radius of the electron

A, B, D Coulomb's Law F=k |q1 * q2| /r2 Electrostatic force cannot exist unless two charges are present.

Which of the following statements are true? Check all that apply. a) The insertion of a dielectric material between the two conductors in a capacitor allows a higher voltage to be applied to the capacitor. b) Dielectrics allow electric charge to flow as easily as they do in air. c) The insertion of a dielectric material between the two conductors in a capacitor allows the plates of the capacitor to be placed closer together without touching. d) After the space between the two conductors in a capacitor is filled with a dielectric material, the capacitance of the capacitor decreases.

A, C

Which of the following will increase the capacitance of a parallel-plate capacitor? Check all that apply. a) Decreasing the separation between the plates will increase the capacitance of a parallel-plate capacitor. b) Increasing the separation between the plates will increase the capacitance of a parallel-plate capacitor. c) Increasing the area of the plates will increase the capacitance of a parallel-plate capacitor. d) Decreasing the area of the plates will increase the capacitance of a parallel-plate capacitor.

A, C

After the adiabatic expansion described in the previous part, the system undergoes a compression that brings it back to its original state. Which of the following statements is/are true? a) The total change in internal energy of the system after the entire process of expansion and compression must be zero. b) The total change in internal energy of the system after the entire process of expansion and compression must be negative. c) The total change in temperature of the system after the entire process of expansion and compression must be positive. d) The total work done by the system must equal the amount of heat exchanged during the entire process of expansion and compression.

A, D

Which of the following statements are true? a- The sum of the changes in potential around any closed loop of a circuit must equal zero. b- Kirchhoff's loop rule is based on the conservation of charge. c- Kirchhoff's junction rule is based on the conservation of energy. d- At any junction point in a circuit, the sum of all the currents entering the junction must equal the sum of all the currents leaving the junction.

A, D

There is a single electron at a distance from the point charge. On which of the following quantities does the electric field at the electron's position depend? a- the distance between the positive charge and the electron b- the charge on the electron c- the mass of the electron d- the charge of the positive charge e- the mass of the positive charge f- the radius of the positive charge g - the radius of the electron

A, E The electric field can be created by only one charge. The value of the electric field depends only on the charge producing the electric field and the distance from that charge.

A negative charge moves in the direction of an electric field. Which of the following statements are true? a) The electric field does negative work on the charge. b) The electric field does not do any work on the charge. c) The sign of the work done on the charge cannot be determined without additional information. d) The potential energy associated with the charge decreases. e) The electric field does positive work on the charge. f) The potential energy associated with the charge increases.

A, F

Consider three resistors with unequal resistances connected in parallel to a battery. Which of the following statements are true? a- The equivalent resistance of the combination of resistors is less than the resistance of any one of the three resistors. b- The voltage across each of the resistors is the same and is equal in magnitude to the voltage of the battery. c- The algebraic sum of the currents flowing through each of the three resistors is equal to the current supplied by the battery. d- The current flowing through each of the resistors is the same and is equal to the current supplied by the battery. e- The equivalent resistance of the combination of resistors is greater than the resistance of any one of the three resistors. f- The algebraic sum of the voltages across the three resistors is equal to the voltage supplied by the battery.

A,B, C

Which of the following statements are true? Check all that apply. a) The electric field between the plates of a parallel-plate capacitor is uniform. b) A capacitor consists of a single sheet of a conducting material placed in contact with an insulating material. c) The capacitance of a capacitor depends upon its structure. d) A capacitor is a device that stores electric potential energy and electric charge.

A,C, D

Which of the following statements are true? a) The electric force acting on a point charge is proportional to the magnitude of the point charge. b) Electric field lines near negative point charges circle clockwise. c) The electric field created by a point charge is constant throughout space. d) In a uniform electric field, the field lines are straight, parallel, and uniformly spaced. e) Electric field lines near positive point charges radiate outward.

A,D,E

A dielectric material, such as Teflon®, is placed between the plates of a parallel-plate capacitor without altering the structure of the capacitor. The charge on the capacitor is held fixed. How is the electric field between the plates of the capacitor affected? a) The electric field becomes zero after the insertion of the Teflon®. b) The electric field decreases because of the insertion of the Teflon®. c) The electric field is not altered, because the structure remains unchanged. d) The electric field becomes infinite because of the insertion of the Teflon®. e) The electric field increases because of the insertion of the Teflon®.

B

Which of the following statements are true? Check all that apply. a) The potential difference between the terminals of a battery, when no current flows to an external circuit, is referred to as the terminal voltage. b) A battery is a device that produces electricity by transforming chemical energy into electrical energy. c) A battery does work on electric charges to bring them to a position of higher electric potential energy so that they can flow through a circuit to a lower potential energy. d) The internal resistance of a battery decreases with decreasing temperature.

B, C

Consider three resistors with unequal resistances connected in series to a battery. Which of the following statements are true? a- The equivalent resistance of the combination of resistors is less than the resistance of any one of the three resistors. b- The equivalent resistance of the combination of resistors is greater than the resistance of any one of the three resistors. c- The algebraic sum of the voltages across the three resistors is equal to the voltage supplied by the battery. d- The current flowing through each of the resistors is the same and is equal to the current supplied by the battery. e- The algebraic sum of the currents flowing through each of the three resistors is equal to the current supplied by the battery. f- The voltage across each of the resistors is the same and is equal in magnitude to the voltage of the battery.

B, C, D

Which of the following statements are true? a) A neutral object contains no charge. b) Two negative charges repel each other. c) Electric charge is quantized. d) Electric charge is conserved. e) Two positive charges attract each other. f) A positive charge and a negative charge attract each other.

B, C, D, F

Which of the following statements are true? a) The resistance of a conductor is proportional to the conductivity of the material of which the conductor is composed. b) Good conductors of electricity have larger conductivity values than insulators. c) A material that obeys Ohm's law reasonably well is called an ohmic conductor or a linear conductor. d) Semiconductors have resistivity values that are larger than those of insulators. e) The resistance of a conductor is proportional to the resistivity of the material of which the conductor is compose

B, C, E

Which of the following will increase the resistance of a wire? a) Increasing the cross-sectional area of the wire will increase the resistance of the wire. b) Increasing the resistivity of the material the wire is composed of will increase the resistance of the wire. c) Increasing the length of the wire will increase the resistance of the wire. d) Decreasing the resistivity of the material the wire is composed of will increase the resistance of the wire. e) Decreasing the length of the wire will increase the resistance of the wire. f) Decreasing the cross-sectional area of the wire will increase the resistance of the wire.

B, C, F

An ideal gas expands through an adiabatic process. Which of the following statements is/are true? a) The work done by the gas is negative, and heat must be added to the system. b) The work done by the gas is positive, and no heat exchange occurs. c) The internal energy of the system has increased. d) The internal energy of the system has decreased.

B, D

Which of the following statements are true for electric field lines? a) Electric field lines are continuous; they do not have a beginning or an ending. b) Electric field lines can never intersect. c) Electric field lines are close together in regions of space where the magnitude the electric field is weak and are father apart where it is strong. d) At every point in space, the electric field vector at that point is tangent to the electric field line through that point. e) Electric field lines point away from positive charges and toward negative charges.

B, D, E

A positive charge moves in the direction of an electric field. Which of the following statements are true? a) The electric field does negative work on the charge. b) The potential energy associated with the charge decreases. c) The electric field does not do any work on the charge. d) The potential energy associated with the charge increases. e) The electric field does positive work on the charge. f) The sign of the work done on the charge cannot be determined without additional information.

B, E

Which of the following statements are true? Check all that apply. a) In a circuit, current is delivered by the positive terminal of a battery, and it is used up by the time it returns to the negative terminal of the battery. b) Current is the total amount of charge that passes through a conductor's full cross section at any point per unit of time. c) By convention, the direction of a current is taken to be the direction of flow for negative charges. d) In order to maintain a steady flow of current in a conductor, a steady force must be maintained on the mobile charges. e) When an electric field is applied to a conductor, the free electrons move only in the direction opposite the applied electric field.

B, E

A parallel-plate capacitor connected to a battery becomes fully charged. After the capacitor from the battery is disconnected, the separation between the plates of the capacitor is doubled in such a way that no charge leaks off. How is the energy stored in the capacitor affected? a) The energy stored in the capacitor is decreased to one-fourth of its original value. b) The energy stored in the capacitor remains constant. c) The energy stored in the capacitor doubles its original value. d) The energy stored in the capacitor quadruples its original value. e) The energy stored in the capacitor is decreased to one-half of its original value.

C V = E*d

A disk with a radius of R is oriented with its normal unit vector at an angle θ with respect to a uniform electric field. Which of the following would result in an increase in the electric flux through the disk? a) increasing the given orientation angle of the disk, but not b) exceeding an angle of 90° c) decreasing the area of the disk d) increasing the strength of the electric field e) increasing the area of the disk f) decreasing the given orientation angle of the disk g) decreasing the strength of the electric field

C,D,E

A parallel-plate capacitor is connected to a battery. After it becomes charged, the capacitor is disconnected from the battery and the plate separation is increased. What happens to the potential difference between the plates? a) More information is needed to answer this question. b) The potential difference between the plates decreases. c) The potential difference between the plates stays the same. d) The potential difference between the plates increases.

D When the capacitor is disconnected from the battery, the charge on the plates cannot change (Q = C∆V). Increasing the distance between the plates decreases the capacitance (C =ϵ0A/d). Therefore, the potential difference must increase.

Does the shape or size of an object affect the total electric flux coming out of that surface?

NO. Just as the shape of the surface does not affect the total electric flux coming out of that surface, its size does not make any difference in the total electric flux either. The only relevant quantity is the total enclosed charge.

A circuit maintains a constant resistance. If the current in the circuit is doubled, what is the effect on the power dissipated by the circuit? The power dissipated remains constant. The power dissipated is reduced by a factor of 2. The power dissipated is quadrupled. The power dissipated is doubled. The power dissipated is reduced by a factor of 4.

The power dissipated is quadrupled. P = V^2/R

A constant voltage is applied across a circuit. If the resistance in the circuit is doubled, what is the effect on the power dissipated by the circuit? The power dissipated is quadrupled. The power dissipated remains constant. The power dissipated is reduced by a factor of 2. The power dissipated is reduced by a factor of 4. The power dissipated is doubled.

The power dissipated is reduced by a factor of 2. P = V^2/R

If the resistivity of copper is less than that of gold at room temperature, which of the following statements must be true? a) Electrons in gold are more likely to be scattered than electrons in copper at room temperature when they are accelerated by the same electric field. b) The sample of gold is thinner than the sample of copper. c) There is more current flowing in the gold than in the copper. d) Gold has a higher resistance than copper.

a) Electrons in gold are more likely to be scattered than electrons in copper at room temperature when they are accelerated by the same electric field.

A net charge is placed on a hollow conducting sphere. How does the net charge distribute itself? a) The net charge uniformly distributes itself on the sphere's outer surface. b) The net charge clumps together at some location within the sphere. c) The net charge uniformly distributes itself on the sphere's inner and outer surfaces. d) The net charge uniformly distributes itself throughout the thickness of the conducting sphere. e) The net charge uniformly distributes itself on the sphere's inner surface.

a) The net charge uniformly distributes itself on the sphere's outer surface.

A monatomic ideal gas expands at constant pressure. Is heat added to the system or taken from the system during this process? a) heat is added to the system b) heat is taken from the system

a) heat is added to the system

Two charged objects separated by some distance attract each other. If the charges on both objects are doubled with no change in distance between them, what happens to the magnitude of the force between the objects? a)The force between them quadruples. b) The force between them is quartered. c) The force between them is halved. d) The force between them remains unchanged. e) The force between them also doubles.

a)The force between them quadruples. Fe = k |q1| |q2|/ r^2

As additional resistors are connected in parallel to a constant voltage source, how is the power supplied by the source affected? a) The power supplied by the sources remains constant. b) The power supplied by the source increases. c) The power supplied by the source decreases. d) The effect on the power supplied by the source cannot be determined without knowing the voltage of the source.

b) The power supplied by the source increases. remember the light bulb experiments with parallel vs series light bulbs

Is it possible for the electric field between two positive charges to equal zero along the line joining the two charges? a) This cannot be determined without knowing the separation between the two charges. b) Yes, regardless of the magnitude of the two charges. c) No, a zero electric field cannot exist between the two charges. d) Yes, but only if the two charges are equal in magnitude.

b) Yes, regardless of the magnitude of the two charges.

As additional resistors are connected in series to a constant voltage source, how is the power supplied by the source affected? a - The power supplied by the source increases. b- The power supplied by the source decreases. c- The effect on the power supplied by the source cannot be determined without knowing the voltage of the source. d- The power supplied by the sources remains constant.

b- The power supplied by the source decreases. ?????

Two charged objects are separated by some distance. The charge on the first object is greater than the charge on the second object. How does the force between the two objects compare? a) The charged objects exert electrostatic forces on each other that are equal in magnitude and pointing in the same direction. b) The first object exerts a large electrostatic force on the second object. c) The charged objects exert electrostatic forces on each other that are equal in magnitude and opposite in direction. d) The second object exerts a large electrostatic force on the first object.

c) The charged objects exert electrostatic forces on each other that are equal in magnitude and opposite in direction.

A solid conducting sphere is placed in an external uniform electric field. With regard to the electric field on the sphere's interior, which statement is correct? a) The interior field points in a direction opposite to the exterior field. b) The interior field points in a direction perpendicular to the exterior field. c) There is no electric field on the interior of the conducting sphere. d) The interior field points in a direction parallel to the exterior field.

c) There is no electric field on the interior of the conducting sphere. The induced charges produce a field withing the conductor that exactly cancels the external field. E = 0 inside the conductor.

If the voltage across a circuit of constant resistance is doubled, how is the current in the circuit affected? a) The current remains constant. b) The current is reduced by a factor of 4. c) The current is doubled. d) The current is quadrupled. e) The current is reduced by a factor of 2.

c, the current is doubled

In a series circuit with two identical bulbs, what happens to the remaining bulb when one is replaced with a wire? a- The remaining bulb maintains the same brightness. b- The remaining bulb gets dimmer. c- The remaining bulb gets brighter. d- The remaining bulb goes out.

c- The remaining bulb gets brighter.

A positively charged rod is brought close to one end of an uncharged metal rod but does not actually touch it. What type of charge does the end of the metal rod closest to the positively charged rod acquire? a) The end of the metal rod closest to the positively charged rod can acquire either a positive or negative charge, depending on the composition of the metal. b) The end of the metal rod closest to the positively charged rod acquires a positive charge. c) The end of the metal rod closest to the positively charged rod remains neutral. d) The end of the metal rod closest to the positively charged rod acquires a negative charge.

d) The end of the metal rod closest to the positively charged rod acquires a negative charge

A plastic rod is rubbed with a fur. During the rubbing process, the rod acquires a negative charge. What type of charge does the fur acquire? a) The fur acquires either a negative or positive charge, depending on how hard the rod was rubbed. b) The fur remains neutral. c) The fur also acquires a negative charge. d) The fur acquires a positive charge.

d) The fur acquires a positive charge.

What happens to the current supplied by the battery when you add an identical bulb in parallel to the original bulb? a- The current is cut in half. b- The current stays the same. c- The current becomes zero. d- The current doubles.

d- The current doubles.

A wire of resistance R is stretched uniformly (keeping its volume constant) until it is twice its original length. What happens to the resistance? R=ϱ(L/A). a) It decreases by a factor of 4. b) It decreases by a factor of 2. c) It stays the same. d) It increases by a factor of 2. e) It increases by a factor of 4.

e) It increases by a factor of 4 R=ϱ(L/A). 2L and 1/2 A --> 4R

If the resistance in a circuit connected to a constant current is halved, how is the voltage in the circuit affected? a- The voltage remains constant. b- The voltage is quadrupled. c- The voltage is reduced by a factor of 4. d- The voltage is doubled. e- The voltage is reduced by a factor of 2.

e- The voltage is reduced by a factor of 2. V=IR

Is the mass of an amber rod after it is charged with fur greater than, less than, or the same as its mass before the charging? (amber: ---, fur: ++++++)

greater than its charge will be less negative, it will have gained e- and, therefore, mass.

An electron and a proton separated by distance d are released from rest simultaneously. The two particles are free to move. When they collide, are they at the midpoint of their initial separation, closer to the initial position of the proton, or closer to the initial position of the electron?

since the e- moves much faster than the proton, the final position of collision is much closer to the proton. F=ma -> a=F/m m(e-) = -e m(p) = +e