Question 1

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

Accepted Answer

Electrons are transferred from one object to another due to the breaking of molecular bonds, resulting in one object becoming positively charged and the other negatively charged.

Question 2

A glass rod is rubbed with silk and then 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 3

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

Accepted Answer

In conductors, charge resides only on the outer surface, while in insulators, charge can reside in the interior.

Question 4

A neutral atom becomes a positive ion when:

Accepted Answer

It loses one or more electrons.

Question 5

Which law states that the net charge of an isolated system remains constant?

Accepted Answer

Conservation of charge

Question 6

Two point charges, $$q_1$$ and $$q_2$$, are separated by a distance $$r. $$According to Coulomb’s Law, what is the magnitude of the force between them?

Accepted Answer

$$F = \frac{1}{4\pi\$$varepsilon_0$$} \frac{|q_1$ q_2$|}{r^2$}$$

Question 7

A metal sphere is charged by contact with a charged rod. What happens to the charge on the sphere?

Accepted Answer

The sphere acquires the same type of charge as the rod.

Question 8

Which of the following is true about the force between two charges as the distance between them increases?

Accepted Answer

The force decreases as the square of the distance increases.

Question 9

A charged rod is brought near, but does not touch, a neutral metal sphere. What happens to the charges in the sphere?

Accepted Answer

The charges in the sphere redistribute, causing one side to become more positive and the other more negative (polarization).

Question 10

Three charges are placed at the corners of a right triangle: $$q_1 = -50$$\ \mathrm{nC}$$, q_2$ = +50\ \mathrm{nC}$$, and $$q_3 = +30$$\ \mathrm{nC}$$. What is the net force on q_3$ due to the other two charges?

Accepted Answer

The net force is found by vector addition of the forces from $$q_1$$ and $$q_2$$ using $$F = k \frac{|q_1$ q_3$|}{r^2$}$$ and $$F = k \frac{|q_2$ q_3$|}{r^2$}.$$

Question 11

A small glass bead of mass $$15\ \mathrm{mg}$$ and charge $$+10\ \mathrm{nC} is $$placed $$1.0\ \mathrm{cm}$$ below a plastic sphere charged to $$-10\ \mathrm{nC}. $$Will the bead leap upward? (Assume $$g = 9.8\ \mathrm{m/s^2$}$$ and $$k = 8.99 	imes 10^9$\ \mathrm{N\cdot m^2$/C^2$$}$)

Accepted Answer

Yes, because the electrostatic force exceeds the gravitational force.

Question 12

Which of the following best describes the result of charging by induction?

Accepted Answer

A neutral object becomes charged without direct contact with the charging object.

Question 13

If two identical metal spheres are touching and a positively charged rod is brought near them (but not touching), then the spheres are separated and the rod is removed, what are the final charges on the spheres?

Accepted Answer

One sphere is negatively charged and the other is positively charged.

Question 14

Which of the following is the value of the fundamental unit of charge $$e$$?

Accepted Answer

$$e = 1.60 	imes 10$$^{-19}$$\ \mathrm{C}$$

Question 15

Which of the following is NOT a property of electric charge?

Accepted Answer

Electric charge can be created or destroyed in an isolated system.

Question 16

A neutral rod is brought near a charged electroscope. What happens to the leaves of the electroscope?

Accepted Answer

There is no effect because the rod is neutral.

Question 17

Which of the following best explains why a charged rod can attract small pieces of paper?

Accepted Answer

The electric field of the rod induces a separation of charge in the paper, causing attraction.

Question 18

If a plastic rod is rubbed with wool and then brought near a metal sphere connected to the ground, what happens?

Accepted Answer

Electrons flow from the sphere to the ground, leaving the sphere positively charged.

Electric Charge and Coulomb’s Law: Fundamental Concepts and Experiments

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