Physics Chapter 16

A cubic block of aluminum rests on a wooden table in a region where a uniform electric field is directed straight upward. What can be said concerning the charge on the block's top surface? A) The top surface is charged positively. B) The top surface is charged negatively. C) The top surface is neutral. D) The top surface's charge cannot be determined without further information.

A

Three identical charges of 3.0 mC are placed at the vertices of an equilateral triangle which measures 30 cm on a side. What is the magnitude of the electrostatic force which acts on any one of the charges? A) 1.6 N B) 1.8 N C) 2.0 N D) 2.2 N

A

Two 1.0-C charges have a force between them of 1.0 N. How far apart are they? A) 95 km B) 9.5 m C) 4.0 m D) 4.0 mm

A

Two charged objects attract each other with a certain force. If the charges on both objects are doubled with no change in separation, the force between them A) quadruples. B) doubles. C) halves. D) increases, but we can't say how much without knowing the distance between them.

A

Materials in which the electrons are bound very loosely to the nuclei and can move about freely within the material are referred to as A) insulators. B) conductors. C) semiconductors. D) superconductors.

B

A +3.0-C charge is at the origin and a +9.0-C charge is at x = 4.0 m. Where on the x-axis can a third charge be placed so the net force on it is zero? A) x = 0.50 m B) x = 0.60 m C) x = 1.5 m D) x = 2.4 m

C

A 5.0-C charge is 10 m from a small test charge. What is the magnitude of the electric field at the location of the test charge? A) 4.5 x 10^6 N/C B) 4.5 x 10^7 N/C C) 4.5 x 10^8 N/C D) 4.5 x 10^9 N/C

C

A copper penny has a mass of 3.0 g. A total of 4.0 x 10^12 electrons are transferred from one neutral penny to another. If the electrostatic force of attraction between the pennies is equal to the weight of a penny, what is the separation between them? A) 31 cm B) 33 cm C) 35 cm D) 37 cm

C

A metal sphere of radius 2.0 cm carries a charge of 3.0 mC. What is the electric field 6.0 cm from the center of the sphere? A) 4.2 x 10^6 N/C B) 5.7 x 10^6 N/C C) 7.5 x 10^6 N/C D) 9.3 x 10^6 N/C

C

An originally neutral electroscope is briefly touched with a positively charged glass rod. The electroscope A) remains neutral. B) becomes negatively charged. C) becomes positively charged. D) could become either positively or negatively charged, depending on the time of contact.

C

If a solid metal sphere and a hollow metal sphere of equal diameters are each given the same charge, the electric field (E) midway between the center and the surface is A) greater for the solid sphere than for the hollow sphere. B) greater for the hollow sphere than for the solid sphere. C) zero for both. D) equal in magnitude for both, but one is opposite in direction from the other.

C

Two 0.20-g metal spheres are hung from a common point by nonconducting threads which are 30 cm long. Both are given identical charges, and the electrostatic repulsion forces them apart until the angle between the threads is 20e. How much charge was placed on each sphere? A) 10 nC B) 15 nC C) 20 nC D) 25 nC

C

Two charged objects are separated by a distance d. The first charge is larger in magnitude than the second charge. A) The first charge exerts a larger force on the second charge. B) The second charge exerts a larger force on the first charge. C) The charges exert forces on each other equal in magnitude and opposite in direction. D) The charges exert forces on each other equal in magnitude and pointing in the same direction.

C

A neutral atom always has A) more neutrons than protons. B) more protons than electrons. C) the same number of neutrons as protons. D) the same number of protons as electrons.

D

Electric field lines near positive charges a circle A) circle clockwise. B) circle counter-clockwise. C) radiate inward. D) radiate outward.

D

Two point charges of +3.0 mC and -7.0 mC are placed at x = 0 and x = 0.20 m. What is the magnitude of the electric field at the point midway between them? A) 1.8 x 10^6 N/C B) 3.6 x 10^6 N/C C) 4.5 x 10^6 N/C D) 9.0 x 10^6 N/C

D

A large negatively charged object is placed on an insulated table. A neutral metallic ball rolls straight toward the object, but stops before it touches it. A second neutral metallic ball rolls along the path followed by the first ball, strikes the first ball, and stops. The first ball rolls forward, but does not touch the negative object. At no time does either ball touch the negative object. What is the final charge on each ball? A) The first ball is positive, and the second ball is negative. B) The first ball is negative, and the second ball is positive. C) Both balls remain neutral. D) Both balls are positive.

A

A piece of plastic has a net charge of +2.00 mC. How many more protons than electrons does this piece of plastic have? A) 1.25 x 10^13 B) 1.25 x 10^19 C) 2.50 x 10^13 D) 2.50 x 10^19

A

A point charge of +Q is placed at the center of a square. When a second point charge of -Q is placed at one of the square's corners, it is observed that an electrostatic force of 2.0 N acts on the positive charge at the square's center. Now, identical charges of -Q are placed at the other three corners of the square. What is the magnitude of the net electrostatic force acting on the positive charge at the center of the square? A) zero B) 2.8 N C) 4.0 N D) 8.0 N

A

A positive point charge is enclosed in a hollow metallic sphere that is grounded. As compared to the case without the hollow sphere, the electric field at a point directly above the hollow sphere has A) diminished to zero. B) diminished somewhat. C) increased somewhat. D) not changed.

A

A proton carries a A) positive charge. B) neutral charge. C) negative charge. D) variable charge.

A

An electron and a proton are separated by a distance of 1.0 m. What happens to the size of the force on the proton if the electron is moved 0.50 m closer to the proton? A) It increases to 4 times its original value. B) It increases to 2 times its original value. C) It decreases to one-half its original value. D) It decreases to one-fourth its original value.

A

Consider a square which is 1.0 m on a side. Charges are placed at the corners of the square as follows: +4.0 mC at (0, 0); +4.0 mC at (1, 1); +3.0 mC at (1, 0); -3.0 mC at (0, 1). What is the magnitude of the electric field at the square's center? A) 1.1 x 10^5 N/C B) 1.3 x 10^5 N/C C) 1.5 x 10^5 N/C D) 1.7 x 10^5 N/C

A

Is it possible for a positive and a negative charge to attract each other? A) Yes, they always attract. B) Yes, they will attract if they are close enough. C) Yes, they will attract if one carries a larger charge than the other. D) No, they will never attract.

A

Materials in which the electrons are bound very tightly to the nuclei are referred to as A) insulators. B) conductors. C) semiconductors. D) superconductors.

A

The charge carried by one electron is e = -1.6 x 10-19 C. The number of electrons necessary to produce a charge of -1.0 C is A) 6.25 x 10^18. B) 6.25 x 10^9. C) 1.6 x 10^19. D) none of the given answers

A

The electric field shown FIGURE 16-2 A) increases to the right. B) increases down. C) decreases to the right. D) decreases down. E) is uniform

A

Three identical point charges of 2.0 mC are placed on the x-axis. The first charge is at the origin, the second to the right at x = 50 cm, and the third is at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin? A) 0.18 N left B) 0.18 N right C) 0.36 N left D) 0.36 N right

A

Three point charges are placed on the x-axis. A charge of +2.0 mC is placed at the origin, -2.0 m C to the right at x = 50 cm, and +4.0 mC at the 100 cm mark. What are the magnitude and direction of the electrostatic force which acts on the charge at the origin? A) 0.072 N right B) 0.072 N left C) 0.14 N right D) 0.14 N left

A

Two point charges each have a value of 3.0 C and are separated by a distance of 4.0 m. What is the electric field at a point midway between the two charges? A) zero B) 9.0 x 10^7 N/C C) 18 x 10^7 N/C D) 4.5 x 10^7 N/C

A

State three properties of conductors in static equilibrium.

(1) The electric field inside a conductor is zero in the static situation. (2) Any net charge on a conductor distributes itself on the surface. (3) The electric field is always perpendicular to the surface outside of a conductor.

A 5.0-C charge is 10 m from a small test charge. What is the direction of the electric field? A) toward the 5.0 C B) away from the 5.0 C C) perpendicular to a line joining the charges D) none of the given answers

B

A 5.0-C charge is 10 m from a small test charge. What is the magnitude of the force experienced by a 1.0 nC charge placed at the location of the test charge? A) 0.045 N B) 0.45 N C) 4.5 N D) 45 N

B

A force of 10 N acts on a charge of 5.0 mC when it is placed in a uniform electric field. What is the magnitude of this electric field? A) 50 MN/C B) 2.0 MN/C C) 0.50 MN/C D) 1000 MN/C

B

A glass rod is rubbed with a piece of silk. During the process the glass rod acquires a positive charge and the silk A) acquires a positive charge also. B) acquires a negative charge. C) remains neutral. D) could either be positively charged or negatively charged. It depends on how hard the rod was rubbed.

B

A metal sphere of radius 10 cm carries a charge of +2.0 mC. What is the magnitude of the electric field 5.0 cm from the sphere's surface? A) 4.0 x 10^5 N/C B) 8.0 x 10^5 N/C C) 4.0 x 10^7 N/C D) 8.0 x 10^7 N/C

B

A negatively charged rod is brought near one end of an uncharged metal bar. The end of the metal bar farthest from the charged rod will be charged A) positive. B) negative. C) neutral. D) none of the given answers

B

A point charge of +Q is placed at the center of a square, and a second point charge of -Q is placed at the upper-left corner. It is observed that an electrostatic force of 2.0 N acts on the positive charge at the center. What is the magnitude of the force that acts on the center charge if a third charge of -Q is placed at the lower-left corner? FIGURE 16-3 A) zero B) 2.8 N C) 4.0 N D) 5.3 N

B

A point charge of +Q is placed at the centroid of an equilateral triangle. When a second charge of +Q is placed at one of the triangle's vertices, an electrostatic force of 4.0 N acts on it. What is the magnitude of the force that acts on the center charge due to a third charge of +Q placed at one of the other vertices? FIGURE 16-1 A) zero B) 4.0 N C) 8.0 N D) 16 N

B

A point charge of +Q is placed at the centroid of an equilateral triangle. When a second charge of +Q is placed at one of the triangle's vertices, an electrostatic force of 4.0 N acts on it. What is the magnitude of the force that acts on the center charge due to a third charge of +Q placed at one of the other vertices? FIGURE 16-4 A) zero B) 4.0 N C) 8.0 N D) 16 N

B

A positive object touches a neutral electroscope, and the leaves separate. Then a negative object is brought near the electroscope, but does not touch it. What happens to the leaves? A) They separate further. B) They move closer together. C) They are unaffected. D) cannot be determined without further information

B

An atom has more electrons than protons. The atom is A) a positive ion. B) a negative ion. C) a superconductor. D) impossible.

B

An atomic nucleus has a charge of +40e. What is the magnitude of the electric field at a distance of 1.0 m from the nucleus? A) 5.6 x 10-8 N/C B) 5.8 x 10-8 N/C C) 6.0 x 10-8 N/C D) 6.2 x 10-8 N/C

B

An electron and a proton are separated by a distance of 1.0 m. What happens to the magnitude of the force on the proton if a second electron is placed next to the first electron? A) It quadruples. B) It doubles. C) It will not change. D) It goes to zero.

B

An originally neutral electroscope is grounded briefly while a positively charged glass rod is held near it. After the glass rod is removed, the electroscope A) remains neutral. B) is negatively charged. C) is positively charged. D) could be either positively or negatively charged, depending on how long the contact with ground lasted.

B

Charge +2q is placed at the origin and charge -q is placed at x = 2a. Where can a third positive charge +q be placed so that the force on it is zero? A) 3.4a B) 6.8a C) 8.6a D) 9.3a

B

Consider point charges of +Q and +4Q, which are separated by 3.0 m. At what point, on a line between the two charges, would it be possible to place a charge of -Q such that the electrostatic force acting on it would be zero? A) There is no such point possible. B) 1.0 m from the +Q charge C) 1.0 m from the +4Q charge D) 0.60 m from the +Q charge

B

How can a negatively charged rod charge an electroscope positively? A) by conduction B) by induction C) by deduction D) It cannot.

B

Is it possible to have a zero electric field value between two positive charges along the line joining the two charges? A) Yes, if the two charges are equal in magnitude. B) Yes, regardless of the magnitude of the two charges. C) No, a zero electric field cannot exist between the two charges. D) cannot be determined without knowing the separation between the two charges

B

The model of the atom shows a A) neutrally charged nucleus surrounded by both protons and electrons. B) nucleus consisting of both protons and neutrons, surrounded by a cloud of electrons. C) nucleus consisting of both electrons and neutrons, surrounded by a cloud of protons. D) nucleus consisting of both protons and electrons, surrounded by a cloud of neutrons

B

Three 3.0 mC charges are at the three corners of an square of side 0.50 m. The last corner is occupied by a -3.0 mC charge. Find the electric field at the center of the square. A) 2.2 x 10^5 N/C B) 4.3 x 10^5 N/C C) 6.1 x 10^5 N/C D) 9.3 x 10^5 N/C

B

A foam ball of mass 0.150 g carries a charge of -2.00 nC. The ball is placed inside a uniform electric field, and is suspended against the force of gravity. What are the magnitude and direction of the electric field? A) 573 kN/C down B) 573 kN/C up C) 735 kN/C down D) 735 kN/C up

C

A particle with a charge of 4.0 mC has a mass of 5.0 x 10-3 kg. What electric field directed upward will exactly balance the weight of the particle? A) 4.1 x 10^2 N/C B) 8.2 x 10^2 N/C C) 1.2 x 10^4 N/C D) 5.1 x 10^6 N/C

C

Is it possible to have a zero electric field value between a negative and positive charge along the line joining the two charges? A) Yes, if the two charges are equal in magnitude. B) Yes, regardless of the magnitude of the two charges. C) No, a zero electric field cannot exist between the two charges. D) cannot be determined without knowing the separation between the two charges

C

Q1 = 6.0 nC is at (0.30 m, 0); Q2 = -1.0 nC is at (0, 0.10 m); Q3 = 5.0 nC is at (0, 0). What is the magnitude of the net force on the 5.0 nC charge? A) 3.0 x 10-6 N B) 4.5 x 10-6 N C) 5.4 x 10-6 N D) 7.2 x 10-6 N

C

Sphere A carries a net charge and sphere B is neutral. They are placed near each other on an insulated table. Which statement best describes the electrostatic force between them? A) There is no force between them since one is neutral. B) There is a force of repulsion between them. C) There is a force of attraction between them. D) The force is attractive if A is charged positively and repulsive if A is charged negatively

C

Sphere A carries a net positive charge, and sphere B is neutral. They are placed near each other on an insulated table. Sphere B is briefly touched with a wire that is grounded. Which statement is correct? A) Sphere B remains neutral. B) Sphere B is now positively charged. C) Sphere B is now negatively charged, D) The charge on sphere B cannot be determined without additional information.

C

The force between a 30-mC charge and a -90-mC charge is 1.8 N. How far apart are they? A) 1.9 m B) 2.3 m C) 3.7 m D) 4.2 m

C

Two point charges, separated by 1.5 cm, have charge values of 2.0 and -4.0 mC, respectively. What is the magnitude of the electric force between them? A) 400 N B) 360 N C) 320 N D) 160 N

C

What are the magnitude and direction of the electric field at a distance of 1.50 m from a 50.0-nC charge? A) 20 N/C away from the charge B) 20 N/C toward the charge C) 200 N/C away from the charge D) 200 N/C toward the charge

C

What is the charge on 1 kg of protons? A) 1.0 C B) 1000 C C) 9.6 x 10^7 C D) 6.0 x 10^26 C

C

Which of the following is not a vector? A) electric force B) electric field C) electric charge D) electric line of force

C

A 1.0-C charge is 15 m from a second charge, and the force between them is 1.0 N. What is the magnitude of the second charge? A) 25 C B) 1.0 C C) 0.025 C D) 25 nC

D

A 5.0-mC charge is placed at the 0 cm mark of a meter stick and a -4.0 mC charge is placed at the 50 cm mark. At what point on a line joining the two charges is the electric field zero? A) 1.4 m from the 0 cm mark B) 2.9 m from the 0 cm mark C) 3.3 m from the 0 cm mark D) 4.7 m from the 0 cm mark

D

A 5.0-mC charge is placed at the 0 cm mark of a meter stick and a -4.0 mC charge is placed at the 50 cm mark. What is the electric field at the 30 cm mark? A) 4.0 x 10^5 N/C B) 5.0 x 10^5 N/C C) 9.0 x 10^5 N/C D) 1.4 x 10^6 N/C

D

A Styrofoam ball of mass 0.120 g is placed in an electric field of 6000 N/C pointing downward. What charge must be placed on the ball for it to be suspended? A) -16.0 nC B) -57.2 nC C) -125 nC D) -196 nC

D

A solid block of metal in electrostatic equilibrium is placed in a uniform electric field. Give a statement concerning the electric field in the block's interior. A) The interior field points in a direction opposite to the exterior field. B) The interior field points in a direction that is at right angles to the exterior field. C) The interior points in a direction that is parallel to the exterior field. D) There is no electric field in the block's interior.

D

An electron and a proton are separated by a distance of 1.0 m. What happens to the magnitude of the force on the first electron if a second electron is placed next to the proton? A) It doubles. B) It does not change. C) It is reduced to half. D) It becomes zero.

D

An electron is held up against the force of gravity by the attraction of a fixed proton some distance above it. How far above the electron is the proton? A) 1.5 m B) 2.3 m C) 3.7 m D) 5.1 m

D

At twice the distance from a point charge, the strength of the electric field A) is four times its original value. B) is twice its original value. C) is one-half its original value. D) is one-fourth its original value.

D

Can electric field lines intersect in free space? A) Yes, but only at the midpoint between two equal like charges. B) Yes, but only at the midpoint between a positive and a negative charge. C) Yes, but only at the centroid of an equilateral triangle with like charges at each corner. D) No.

D

Charge is A) quantized. B) conserved. C) invariant. D) all of the given answers

D

If a conductor is in electrostatic equilibrium near an electric charge A) the total charge on the conductor must be zero. B) the force between the conductor and the charge must be zero. C) the total electric field of the conductor must be zero. D) the electric field on the surface of the conductor is perpendicular to the surface.

D

Is it possible for two negative charges to attract each other? A) Yes, they always attract. B) Yes, they will attract if they are close enough. C) Yes, they will attract if one carries a larger charge than the other. D) No, they will never attract.

D

Q1 = 6.0 nC is at (0.30 m, 0); Q2 = -1.0 nC is at (0, 0.10 m); Q3 = 5.0 nC is at (0, 0). What is the direction of the net force on the 5.0 nC charge? A) 34e above +x axis B) 34e above -x axis C) 56e above +x axis D) 56e above -x axis

D

Three point charges are located at the following positions: Q1 = 2.00 mC at x = 1.00 m; Q2 = 3.00 mC at x = 0; Q3 = -5.00 mC at x = -1.00 m. What is the magnitude of the force on the 3.00-mC charge? A) 5.40 x 10-2 N B) 0.135 N C) 8.10 x 10-2 N D) 0.189 N

D

Two charged objects attract each other with a force F. What happens to the force between them if one charge is doubled, the other charge is tripled, and the separation distance between their centers is reduced to one-fourth its original value? The force is now equal to A) 16F. B) 24F. C) (3/8)F. D) 96F.

D

Two charges are separated by a distance d and exert mutual attractive forces of F on each other. If the charges are separated by a distance of d/3, what are the new mutual forces? A) F/9 B) F/3 C) 3F D) 9F

D

Two point charges, initially 2.0 cm apart, experience a 1.0-N force. If they are moved to a new separation of 8.0 cm, what is the electric force between them? A) 4.0 N B) 16 N C) 1/4 N D) 1/16 N

D

What are the units of the Coulomb constant k, which appears in Coulomb's law? A) N*m/C B) N/C C) N2*m/C^2 D) Nœ*2/C^2

D

An atomic nucleus has a charge of +40e. An electron is 10-9 m from the nucleus. What is the force on the electron? A) 2.9 nN B) 1000 C C) 3.7 nN D) 6.8 nN E) 9.2 nN

E

State the law of conservation of electric charge.

The net amount of electric charge produced in any process is zero. or No net electric charge can be created or destroyed.

State Gauss's law

The total flux summed over any closed surface is equal to the net charge enclosed by the surface divided by eo.