Ch 10

If you rub a balloon on your sweater and then press it to a wall, it will often stick there. Why does this happen? A) Rubbing the balloon charges it electrostatically, and this charge on the balloon induces an opposite charge on the wall. The attraction between the induced charge and the charge on the balloon holds the balloon to the wall. B) Rubbing the balloon surface causes it to become slightly conducting. When the balloon is touched to the wall, electrons flow from the balloon to the wall. This sets up an electric field that bonds the balloon weakly to the wall. C) Rubbing the balloon causes moisture to condense on it, and surface tension causes the balloon to stick to the wall. D) Rubbing removes a surface layer of grease, allowing the rubber to come in sufficiently close contact with the wall so that air pressure holds it there. E) A wall typically has a net electric charge on it, and rubbing the balloon charges it electrostatically. If the wall happens to have opposite charge to that on the balloon, the balloon will stick.

A) Rubbing the balloon charges it electrostatically, and this charge on the balloon induces an opposite charge on the wall. The attraction between the induced charge and the charge on the balloon holds the balloon to the wall.

A parallel plate capacitor contains a positively charged plate on the left, and a negatively charged 22) plate on the right. An electron in between the plates is moving to the right. Which statement is true? A) The potential energy of the electron is increasing and it is moving to a region having a lower potential. B) The potential energy of the electron is increasing and it is moving to a region having a higher potential. C) The potential energy of the electron is decreasing and it is moving to a region having a higher potential. D) The potential energy of the electron is decreasing and it is moving to a region having a lower potential.

A) The potential energy of the electron is increasing and it is moving to a region having a lower potential.

The electric field at point P due to a point charge Q a distance R away has magnitude E. In order to 18) double the magnitude of the field at P, you could A) double the charge to 2Q. B) reduce the distance to R/2. C) double the distance to 2R. D) reduce the distance to R/4. E) double the charge to 2Q and at the same time reduce the distance to R/2.

A) double the charge to 2Q

A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the potential energy of the electron A) increases. B) decreases. C) remains the same. D) depends on the zero point of the potential.

A) increases.

As an electron moves from a high potential to a low potential, its electrical potential energy 21) A) increases. B) remains constant. C) decreases.

A) increases.

Four charged particles (two having a charge +Q and two having a charge - Q) are distributed on 20) the xy-plane, as shown below. Each charge is equidistant from the origin. The voltage is zero at infinity. The amount of work required to move a positively charged particle from point P to point O (which is on the z-axis, below the origin) is A) zero. B) negative. C) positive. D) dependent on the path in which the charged is moved.

A) zero. has picture

Two identical small charged spheres are a certain distance apart, and each initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually diminishes on both spheres. When each of the spheres has lost half its initial charge, the magnitude of the electrostatic force will be: A) 1/2 F. B) 1/4 F. C) 1/16 F. D) 1/8 F.

B) 1/4 F

A hydrogen nucleus, which has a charge e, is situated to the left of a carbon nucleus, which has a charge 6e. Which statement is true? A) The electrical force experienced by the hydrogen nucleus is to the right, and the magnitude is equal to the force exerted on the carbon nucleus. B) The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is equal to the force exerted on the carbon nucleus. C) The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is greater than the force exerted on the carbon nucleus. D) The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is less than the force exerted on the carbon nucleus.

B) The electrical force experienced by the hydrogen nucleus is to the left, and the magnitude is equal to the force exerted on the carbon nucleus.

The diagram shows two unequal charges +q and - Q, of opposite sign. Charge Q has greater magnitude than charge q. Point X is midway between the charges. In what section of the line will there be a point where the resultant electric field is zero? A) XY B) V W C) YZ D) W X

B) V W has picture

Two conductors are joined by a long copper wire. Thus A) each conductor carries the same free charge. B) each conductor must be at the same potential. C) the potential on the wire is the average of the potential of each conductor. D) the electric field at the surface of each conductor is the same. E) no free charge can be present on either conductor.

B) each conductor must be at the same potential.

A parallel-plate capacitor having circular plates of diameter D and a distance d apart stores energy 26) U when it is connected across a fixed potential difference. If you want to triple the amount of energy stored in this capacitor by changing only the size of its plates, the diameter should be changed to: A ) 3D B ) 9 D C ) Dsqrt 3 D ) D 3 E ) 3 D

C ) Dsqrt 3

One charged plastic ball is vertically above another in a test tube as shown. The balls are in equilibrium a distance d apart. If the charge on each ball is doubled, the distance between the balls in the test tube would become A) 4d. B) 8d. C) 2d. D)sq root 2d.

C) 2d

) A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallic sphere. It is allowed to touch the sphere for a few seconds, and then is separated from the sphere by a small distance. A fter the rod is separated, the rod A) feels no force due to the sphere. B) is attracted to the sphere. C) is repelled by the sphere.

C) is repelled by the sphere.

Four charged particles (two having a charge +Q and two having a charge - Q) are distributed on 19) the xy-plane, as shown below. Each charge is equidistant from the origin. The voltage is zero at infinity. The voltage at location P, which is on the z axis, is A) positive. B) negative. C) zero. D) impossible to determine based on the information given.

C) zero.

If two macroscopic objects are electrically attracted to each other, A) both objects must be positively charged. B) both objects must be negatively charged. C) one object must be negatively charged and the other object must be positively charged. D) None of the above statements are absolutely true.

D) None of the above statements are absolutely true.

A n electron is initially moving to the right when it enters a uniform electric field directed upwards. Which trajectory shown below will the electron follow? A) Trajectory W B) Trajectory X C) Trajectory Y D) Trajectory Z

D) Trajectory Z

The capacitance of a capacitor depends on A) the potential difference across it. B) the energy stored in it. C) the charge on it. D) More than one of these E) None one of these

E) None one of these

The electrical force between two objects depends on A) the distance between the two objects. B) the mass of the two objects. C) the charge of the two objects. D) A ll of the above E) Two of the above

E) Two of the above

Two uncharged metal spheres, #1 and #2, are mounted on insulating support rods. A third metal sphere, carrying a positive charge, is then placed near #2. Now a copper wire is momentarily connected between #1 and #2 and then removed. Finally, sphere #3 is removed. In this final state A) spheres #1 and #2 are still uncharged. B) sphere #1 carries negative charge and #2 carries positive charge. C) spheres #1 and #2 both carry positive charge. D) spheres #1 and #2 both carry negative charge. E) sphere #1 carries positive charge and #2 carries negative charge

E) sphere #1 carries positive charge and #2 carries negative charge

A positive test charge q is released near a positive fixed charge Q. As q moves away from Q, it will move with A) increasing acceleration. B) constant acceleration. C) constant velocity. D) decreasing acceleration

HAS PICTURE D) decreasing acceleration

X and Y are two uncharged metal spheres on insulating stands, and are in contact with each other. A positively charged rod R is brought close to X as shown in figure 1. Sphere Y is now moved away from X (figure 2). The final charge states of X and Y, respectively, are A) neutral and neutral. B) negative and positive. C) positive and neutral. D) neutral and positive.

HAS PICTURE B) negative and positive.

Suppose a region of space has a uniform electric field, directed toward the right, as shown in the 24) figure. Which statement is true?

The voltage at points A and B are equal, and the voltage at point C is lower than the voltage at point A.

Two equal and opposite charges a certain distance apart are called an electric "dipole." A positive test charge +q is placed as shown, equidistant from the two charges. Which diagram below gives the direction of the net force on the test charge?

answer is pictures

Two identically charged balls are a certain distance apart. The vectors in the diagram below show the magnitude and direction of the electrostatic force on each ball. Suppose the charge on the left ball is now doubled (represented by two plus signs). Which diagram below best represents the forces that now act on the two balls?

answer is pictures

The diagram shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: i. The charge on P is smaller than the charge on Q. ii. The electrostatic force on P is smaller than that on Q. Which of the above statements are true? A) Only i B) Only ii C) Both i and ii D) Neither i nor ii

has picture A) Only i

Four charged particles (two having a charge +Q and two having a charge - Q) are distributed as shown below. Each charge is equidistant from the origin. In which direction is the net electric field at the point P, which is on the y axis? A) directly left (negative x direction) B) directly up (in the positive y direction) C) upwards, toward the right D) upwards, toward the left E) The net field is zero, so there is no direction.

has pictures D) upwards, toward the left

A proton is accelerated from rest through a potential difference V0 and gains a speed v0. If it were 28) accelerated instead through a potential difference of 2V0, it would gain a speed: A)8v0 B)2v0 C)v0 2 D)4v0

v0sqrt2