Q: Given two point charges, $$q_1 = +2$$\ \mu\mathrm{C}$$ and q_2$ = -3\ \mu\mathrm{C}$$, separated by $$0.5\ \mathrm{m}$$, what is the magnitude of the force between them? Use $$k = 8.988 \times 10^9$\ \mathrm{N\,m^2$/C^2$$}$.

$$F = k \frac{|q_1$ q_2$|}{r^2$} = 8.988 \times 10^9$ \frac{2 \times 10$$^{-6}$$ \times 3 \times 10$$^{-6}$$}{0.25} = 0.216\ \mathrm{N}$$

Question 1

Which of the following statements best describes the Law of Conservation of Charge?

Accepted Answer

The net charge in an isolated system is conserved; charge cannot be created or destroyed.

Question 2

A bird is flying east at $$8\ \mathrm{m/s}$$ while the wind is blowing north at $$6\ \mathrm{m/s}. $$What is the bird's ground speed?

Accepted Answer

$$\sqrt{8^2$ + 6^2$} = 10\ \mathrm{m/s}$$

Question 3

When a rubber rod is rubbed with fur, what happens to the rod?

Accepted Answer

It gains electrons and becomes negatively charged.

Question 4

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

Accepted Answer

Coulomb (C)

Question 5

A neutral lithium atom has 3 protons, 4 neutrons, and 3 electrons. What is its net charge?

Accepted Answer

$$0$$

Question 6

Which of the following best explains why a charged object can attract a neutral insulator?

Accepted Answer

The charged object induces a separation of charge within the insulator, creating attraction.

Question 7

Given two point charges, $$q_1 = +2$$\ \mu\mathrm{C}$$ and q_2$ = -3\ \mu\mathrm{C}$$, separated by $$0.5\ \mathrm{m}$$, what is the magnitude of the force between them? Use $$k = 8.988 	imes 10^9$\ \mathrm{N\,m^2$/C^2$$}$.

Accepted Answer

$$F = k \frac{|q_1$ q_2$|}{r^2$} = 8.988 	imes 10^9$ \frac{2 	imes 10$$^{-6}$$ 	imes 3 	imes 10$$^{-6}$$}{0.25} = 0.216\ \mathrm{N}$$

Question 8

Which of the following is true about conductors and insulators?

Accepted Answer

Conductors allow easy movement of charge, while insulators do not.

Question 9

A glass rod is rubbed with silk. After rubbing, the glass rod becomes:

Accepted Answer

Positively charged because it loses electrons.

Question 10

Which equation correctly expresses Coulomb’s Law for 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 11

If a neutral atom gains two electrons, what is its resulting charge?

Accepted Answer

$$-2e$$

Question 12

A metal ball is brought near a negatively charged rod but does not touch it. What happens to the charges in the metal ball?

Accepted Answer

Electrons in the ball are repelled, causing one side to become positively charged and the other negatively charged.

Question 13

Which of the following best describes the direction of the electric force between two like charges?

Accepted Answer

The force is repulsive and points away from each other.

Question 14

A charge $$q_1 is $$located at $$(0,0)$$ and $$q_2 at$$ $$(0,3)$$ meters. What is the vector from $$q_1 to$$ $$q_2$$?

Accepted Answer

$$(0,3)$$

Question 15

If $$q_1 = +1.5$$ 	imes $$10^{-3}$$\ \mathrm{C}$$ is at (0$$,0)$$ and q_3$ = +0.2 	imes 10$$^{-3}$$\ \mathrm{C} is at$$ $$(-1.2, 0)$$, what is the magnitude of the vector $$\vec{r}_{13}$$ from $$q_1 to$$ $$q_3$$?

Accepted Answer

$$1.2$$

Question 16

Which of the following is the correct value for the charge of a single electron?

Accepted Answer

$$-1.602 	imes 10$$^{-19}$$\ \mathrm{C}$$

Question 17

A positively charged glass rod is brought near a small piece of paper. The paper is attracted to the rod. What is the best explanation?

Accepted Answer

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

Question 18

Which of the following best describes the process of charging a conductor by induction?

Accepted Answer

A charged object is brought near the conductor, causing charge separation, and then the conductor is grounded to allow charge transfer.

Electric Charge and Coulomb’s Law: Foundations of Electrostatics

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