Q: What is the magnitude of the charge of a single electron?

$$1.6 \times 10$$^{-19}$$\ \mathrm{C}$$

Q: Two stationary point charges, $$q_1 = +2$$\ \mathrm{C}$$ and q_2$ = -3\ \mathrm{C}$$, are placed $$0.5\ \mathrm{m}$$ apart in vacuum. What is the magnitude of the force between them?

$$F = 9 \times 10^9$ \times \frac{2 \times 3}{0.5^2$} = 2.16 \times 10$$^{11}$$\ \mathrm{N}$$

Question 1

Which of the following statements best describes the concept of charge conservation in physics?

Accepted Answer

Charge can be moved from one object to another, but the total charge in a closed system remains constant.

Question 2

A glass rod is rubbed with silk, resulting in the rod becoming positively charged. What happens at the atomic level?

Accepted Answer

Electrons are transferred from the glass rod to the silk.

Question 3

Which of the following materials allows both positive and negative charges to move freely?

Accepted Answer

Ionic solutions

Question 4

What is the magnitude of the charge of a single electron?

Accepted Answer

$$1.6 	imes 10$$^{-19}$$\ \mathrm{C}$$

Question 5

Two stationary point charges, $$q_1 = +2$$\ \mathrm{C}$$ and q_2$ = -3\ \mathrm{C}$$, are placed $$0.5\ \mathrm{m}$$ apart in vacuum. What is the magnitude of the force between them?

Accepted Answer

$$F = 9 	imes 10^9$ 	imes \frac{2 	imes 3}{0.5^2$} = 2.16 	imes 10$$^{11}$$\ \mathrm{N}$$

Question 6

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have free electrons that can move throughout the material.

Question 7

A positively charged rod is brought near a neutral metal sphere without touching it. What happens to the charges in the sphere?

Accepted Answer

Electrons in the sphere move toward the rod, causing polarization.

Question 8

Which equation correctly represents Coulomb's Law for the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by distance $$r$$?

Accepted Answer

$$F = k \frac{|q_1$ q_2$|}{r^2$}$$

Question 9

If a plastic rod is rubbed with fur and becomes negatively charged, what is the most likely explanation?

Accepted Answer

Electrons are transferred from the fur to the rod.

Question 10

Which of the following is NOT a property of insulators?

Accepted Answer

Positive ions are free to move.

Question 11

A student arranges four charges at the corners of a square: $$+q$$, $$-2q$$, $$+3q$$, and $$-4q. $$What is the net force on the $$+q$$ charge due to the other three?

Accepted Answer

The net force is the vector sum of the forces from each of the other three charges, calculated using Coulomb's Law.

Question 12

Which of the following best describes the difference between conductors and insulators?

Accepted Answer

Conductors allow free movement of electrons, while insulators do not.

Question 13

What is the value of the Coulomb constant $$k$$ used in Coulomb's Law?

Accepted Answer

$$k = 9 	imes 10^9$\ \mathrm{N \cdot m^2$ / C^2$}$$

Question 14

Which of the following scenarios demonstrates the quantization of electric charge?

Accepted Answer

The charge on any object is always an integer multiple of the elementary charge $$e.$$

Question 15

A charged particle experiences a force due to another nearby charge without any physical contact. What type of force is this?

Accepted Answer

Noncontact force

Question 16

Which of the following best describes the effect of distance on the electric force between two charges?

Accepted Answer

The force decreases as the distance increases, following an inverse square law.

Question 17

A saltwater solution conducts electricity because:

Accepted Answer

It contains both free positive and negative ions.

Question 18

Which of the following is the correct unit for electric charge?

Accepted Answer

Coulomb (C)

Question 19

If two like charges are placed near each other, what type of force do they experience?

Accepted Answer

Repulsive force

Question 20

Which of the following is the permittivity of free space ($$\$$varepsilon_0$$) used in Coulomb's Law?

Accepted Answer

$$\$$varepsilon_0$$ = 8.854 	imes 10$$^{-12}$$\ \mathrm{C^2$ / N \cdot m^2$}$$

Physics 208: Electric Charges, Forces, and Materials

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