chp 23,24,25

The insulating solid sphere in the previous Example 24.5 has the same total charge Q and radius a as the thin shell in the example here. Consider the electric fields due to the sphere (Esphere), the shell (Eshell), and a point charge Q (EQ). Rank the strength of the electric fields due to these three charged objects at the same three points ('1' represents the object with the strongest, '2' for the next in strength and so on. For example, you can have the triad {3, 1, 2} as your answer, or {2, 1, 2} if the shell is strongest while the sphere and the point charge have equal strengths.): (a) r a {2,2,1} /{1,1,1} /{2,1,1} {1,1,2}/{1,2,3} (b) r a {1,1,1}/ {2,3,1} / {1,2,1} {2,1,1}/{2,2,1}

(a) r a {1,1,1} (b) r a {2,3,1}

Three are brought close to each other, two at a time. When objects A and B are brought together, they attract. When objects B and C are brought together, they repel. From this, we conclude which of the following? (Select all that apply.) 1. We need to perform additional tests to determine information about the charges on the objects. 2. All three of the objects possess charges of the same sign. 3. Objects A and C possess charges of the same sign. 4. One of the objects is neutral. 5. Objects A and C possess charges of opposite sign.

1. We need to perform additional tests to determine information about the charges on the objects.

Many types of molecules may be modeled as dipoles. For example, two molecules modeled as simple dipoles are aligned on the x-axis, as shown. Each dipole consists of a positive charge q and negative charge -q, separated by a distance d. The distance between the centers of the two dipoles is x. Considering the forces due to all four charges, the net force of one dipole on the other will be which of the following? a. it depends on the relative distances d and x b. attractive c. zero d. repulsive

B. attractive

Object A has a charge of +2 µC, and object B has a charge of +6 µC. Which statement is true about the electric forces on the objects? FAB = -3FBA FAB = -FBA 3FAB = -FBA FAB = FBA 3FAB = -FBA FAB = 3FBA Correct: Your answer is correct.

Correct: Your answer is correct.correct FAB = -FBA

Two point charges, q1 = +q and q2 = -2q, are fixed at positions on the x-axis, as shown below. If you were to place a third point charge somewhere so that the force on it would be zero, you should place that charge at which location? a. on the x-axis in between the two charges b. off of the x-axis c. on the x-axis to the right of the two charges d on the x-axis to the left of the two charge

D.on the x-axis to the left of the two charge

Which of the following statements about electric field lines associated with electric charges is false? Electric field lines can be either straight or curved. Electric field lines can form closed loops. Electric field lines begin on positive chares and end on negative charges. Electric field lines can never intersect with one another.

Electric field lines can form closed loops.

In a charge-free region of space, a closed container is placed in an electric field. Which of the following is a requirement for the total electric flux through the surface of the container to be zero? a The requirement does not exist -- the total electric flux is zero no matter what. b The field must be uniform. c The container must be oriented in a certain way. d The container must be symmetric.

a The requirement does not exist -- the total electric flux is zero no matter what.

If more electric field lines are leaving a gaussian surface than entering, what can you conclude about the net charge enclosed by that surface? a. The surface must enclose a positive net charge. b.The surface must enclose a negative net charge. c. Not enough information is given to decide.

a. The surface must enclose a positive net charge.

A spherical balloon contains a positively charged object at its center. As the balloon is inflated to a greater volume while the charged object remains at the center, what does the electric potential at the surface of the balloon do? a. remain the same b decrease c. increase What does the the electric flux through the surface of the balloon do? a. remain the same b decrease c. increase

b and a

As illustrated in the figure below, an electric field is produced on the axis of a uniformly charged ring of radius a and total charge Q, at point P a distance x away from the center of the ring. If the charge Q is then spread uniformly into a disk of the same radius at the same location, the electric field at point P a distance x away from the center of this disk will be which of the following? a.less than for the ring b.greater than for the ring c.impossible to determine d. the same as for the ring

b.greater than for the ring

Suppose you have a sphere of radius 1.00 m that carries a charge of +1.00 µC at its center. The radius of the sphere is changed to 0.500 m. What happens to the flux through the sphere and the magnitude of the electric field at the surface of the sphere? a. The flux and field both increase. b The flux increases and the field decreases. c The flux decreases and the field remains the same. d The flux and field both decrease. e The flux remains the same and the field increases. f The flux decreases and the field increases.

e The flux remains the same and the field increases.

Two charged conducting spheres of different radii are connected by a conducting wire, as shown in Figure 25.25. Which sphere has the greater charge density? a larger sphere b smaller sphere

smaller sphere

If you rub an inflated balloon against your hair, the two materials attract each other, as shown in Figure 23.3. The amount of charge present in the system of the balloon and your hair after rubbing is ______________ the amount of charge present before rubbing.

the same as

A negative charge moves in the direction of a uniform electric field. Does the potential energy of the charge increase or decrease? a decrease b increase Does it move to a position of higher or lower potential? a lower potential b higher potential

{1.}correct increase {2.}correct lower potential