Chapter 16 Additional Conceptual Questions

Electrically neutral objects cannot exert an electrical force on each other, but they can exert a gravitational force on each other.

• True

• False

If two objects are electrically attracted to each other

• both objects must be negatively charged

• one object must be negatively charged and the other object must be positively charged

• the objects could be electrically neutral

• both objects must be positively charged

• None of the above statements are absolutely true

A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallicsphere that is insulated from ground. It is allowed to touch the sphere for a few seconds, and thenis separated from the sphere by a small distance. After the rod is separated, the rod

• is attracted to the sphere

• feels no force due to the sphere

• is repelled by the sphere

A negatively-charged plastic rod is brought close to (but does not touch) a neutral metal sphere that is connected to ground. After waiting a few seconds, the ground connection is removed (without touching the sphere), and after that the rod is also removed. The sphere is now

• positively charged

• negatively charged

• neutral

X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y?

• X is neutral and Y is positive

• Both X and Y are negative

• X is positive and Y is neutral

• X is negative and Y is positive

• Both X and Y are neutral

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

• sphere #1 carries negative charge and #2 carries positive charge

• spheres #1 and #2 both carry positive charge

• spheres #1 and #2 both carry negative charge

• spheres #1 and #2 are still uncharged

• sphere #1 carries positive charge and #2 carries negative charge

A negatively-charged rod is brought close to (but does not touch) two neutral spheres that are in contact with each other but insulated from the ground. If the two spheres are then separated, what kind of charge will be on the spheres?

• The sphere near the charged rod becomes negative and the other one becomes positive

• Both spheres become positive

• The spheres do not get any charge

• Both spheres become negative

• The sphere near the charged rod becomes positive and the other one becomes negative

Two tiny beads are 25 cm apart with no other charges or fields present. Bead A carries 10 μC of charge and bead B carries 1 μC. Which one of the following statements is true about the magnitudes of the electric forces on these beads?

• The force on A is 10 times the force on B

• The force on B is 100 times the force on A

• The force on A is exactly equal to the force on B

• The force on B is 10 times the force on A

• The force on A is 100 times the force on B

Two very small plastic balls of equal mass are released from rest. One of them carries +10 μC of excess charge and the other one carries +1μC of charge. No other charges or fields are present. Which of the following statements are true about them as they move away from each other? (There may be more than one correct choice.)

• The acceleration of the 1-μC ball is 10 times that of the 10-μC ball

• The balls always have accelerations of equal magnitude

• The acceleration of the 10-μC ball is 10 times that of the 1-μC ball

• The acceleration of the balls keeps increasing

• The speed of the balls keeps increasing

In outer space, a positive charge q is released near a positive fixed charge Q, as shown in the figure. As q moves away from Q, what is true about the motion of q? (There may be more than one correct choice.)

• It will move with constant acceleration

• It will move with increasing speed

• It will move with increasing acceleration

• It will move with decreasing speed

• It will move with decreasing acceleration