Enrico says that positive charge is created when you rub a glass rod with silk, and that negative charge is simply the absence of positive charge. Rosetta says that negative charge is created and that positive charge is the absence of positive charge. (She has heard that Ben Franklin should have reversed the signs he associated with the charges.) Which one, if either, is correct?
a. Enrico, because there really is only one kind of charge.
b. Rosetta, because there really is only one kind of charge.
c. Neither: although no charge is present originally, both types of charge are created through friction.
d. Both: only one type of charge is created by friction at any one time.
e. Neither: both negative and positive charge are present simultaneously in all solid materials on Earth and the process described involves a transfer of charge, not the creation of charge.
[Ques. 2] Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that
a. Y has a negative charge.
b. Z has a negative charge.
c. Y has a positive charge.
d. Z is neutral (has no net charge).
e. Y is negatively charged or neutral (has no net charge).
[Ques. 3] Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that
a. Y has a negative charge.
b. Z has a negative charge.
c. Y has a positive charge.
d. Z has a positive charge.
e. Z is neutral (has no net charge).
[Ques. 4] Rubber rods charged by rubbing with cat fur repel each other. Glass rods charged by rubbing with silk repel each other. A rubber rod and a glass rod charged respectively as above attract each other. A possible explanation is that
a. any two rubber rods charged this way have opposite charges on them.
b. any two glass rods charged this way have opposite charges on them.
c. a rubber rod and a glass rod charged this way have opposite charges on them.
d. all rubber rods always have an excess of positive charge on them.
e. all glass rods always have an excess of negative charge on them.
[Ques. 5] A charge of 50-C is placed on the y axis at y = 3.0 cm and a 77-C charge is placed on the x axis at x = 4.0 cm. If both charges are held fixed, what is the magnitude of the initial acceleration of an electron released from rest at the origin?
a. 1.2 1020 m/s2
b. 1.5 1020 m/s2
c. 1.0 1020 m/s2
d. 1.8 1020 m/s2
e. 2.0 1020 m/s2
[Ques. 6] A point charge (5.0 C) is placed on the x axis at x = 4.0 cm, and a second charge (+5.0 C) is placed on the x axis at x = 4.0 cm. What is the magnitude of the electric force on a third charge (+2.5 C) placed on the y axis at y = 3.0 cm?
a. 90 N
b. 45 N
c. 54 N
d. 72 N
e. 36 N
[Ques. 7] Identical point charges Q are placed at each of the four corners of a 3.0-m 4.0-m rectangle. If Q = 40 C, what is the magnitude of the electrostatic force on any one of the charges?
a. 3.0 N
b. 2.4 N
c. 1.8 N
d. 3.7 N
e. 2.0 N
[Ques. 8] Three identical point charges Q are placed at the vertices of an equilateral triangle (length of each side = 2.0 m). If Q = 60 C, what is the magnitude of the electrostatic force on any one of the charges?
a. 25 N
b. 19 N
c. 14 N
d. 22 N
e. 16 N
[Ques. 9] Three point charges, two positive and one negative, each having a magnitude of 20 C are placed at the vertices of an equilateral triangle (30 cm on a side). What is the magnitude of the electrostatic force on one of the positive charges?
a. 69 N
b. 40 N
c. 80 N
d. 57 N
e. 20 N
[Ques. 10] Three point charges, two positive and one negative, each having a magnitude of 20 C are placed at the vertices of an equilateral triangle (30 cm on a side). What is the magnitude of the electrostatic force on the negative charge?
a. 80 N
b. 40 N
c. 69 N
d. 57 N
e. 75 N
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