Question 1

Which of the following statements best describes the behavior of electric charges according to Coulomb's law?

Accepted Answer

The electric force between two charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them: $$F = k_e \frac{|q_1$ q_2$|}{r^2$}.$$

Question 2

A plastic rod is rubbed with wool and then brought near small pieces of paper. The paper is attracted to the rod. What is the best explanation for this phenomenon?

Accepted Answer

The charged rod induces a separation of charge in the neutral paper, resulting in an attractive force.

Question 3

Which of the following materials is most likely to allow charge to move freely through it?

Accepted Answer

Copper, because it is a conductor.

Question 4

If a glass rod rubbed with silk is brought near a plastic rod rubbed with wool, what will happen?

Accepted Answer

The rods will attract each other because they have opposite types of charge.

Question 5

A neutral metal sphere is touched by a negatively charged plastic rod. What happens to the sphere?

Accepted Answer

The sphere acquires a net negative charge due to the transfer of electrons.

Question 6

Which of the following best describes the process of charging by friction?

Accepted Answer

Electrons are transferred from one object to another, resulting in one object becoming negatively charged and the other positively charged.

Question 7

Which of the following is true about the electric field created by a positive point charge?

Accepted Answer

The electric field points radially outward from the charge at all points in space.

Question 8

A student touches a charged rod and finds that it no longer attracts small pieces of paper. What is the best explanation for this observation?

Accepted Answer

The rod has been discharged by transferring its excess charge to the student.

Question 9

Three identical metal spheres have charges of $$+4\ \mathrm{nC}$$, $$-2\ \mathrm{nC}$$, and $$-1\ \mathrm{nC}$$, respectively. Spheres P and Q are touched together and then separated. Next, Q and R are touched together and separated. What is the final charge on sphere R?

Accepted Answer

$$-0.5\ \mathrm{nC}$$

Question 10

Which of the following statements about conductors and insulators is correct?

Accepted Answer

In conductors, electrons are free to move throughout the material, while in insulators, electrons are tightly bound to their atoms.

Question 11

A positively charged glass rod is brought near a neutral metal sphere. What happens to the charges in the sphere?

Accepted Answer

Electrons in the sphere are attracted toward the rod, causing the side near the rod to become negatively charged.

Question 12

Which of the following best explains why lightning is an example of electrostatics in nature?

Accepted Answer

Lightning is caused by the buildup and sudden discharge of electric charge between clouds and the ground.

Question 13

Which of the following is a consequence of the law of conservation of charge?

Accepted Answer

The total electric charge in an isolated system remains constant.

Question 14

A neutral atom becomes a positive ion when:

Accepted Answer

It loses one or more electrons.

Question 15

Which of the following best describes the difference between charging by conduction and charging by induction?

Accepted Answer

Charging by conduction involves direct contact and transfer of electrons, while charging by induction does not require contact.

Question 16

Which of the following equations correctly gives the magnitude of the electric field $$E$$ created by a point charge $$q at a $$distance $$r$$?

Accepted Answer

$$E = k_e \frac{|q|}{r^2$}$$

Question 17

A student claims that a neutral object cannot be attracted to a charged object. Which of the following best refutes this claim?

Accepted Answer

A charged object can induce a separation of charge in a neutral object, resulting in attraction.

Electrostatics: Electric Charges and Forces

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