Q: A $+8\ \mu\text{C}$ charge and a $+2\ \mu\text{C}$ charge are separated by $4$ m. At what point along the line joining them is the net electric field zero?

Closer to the $+2\ \mu\text{C}$ charge, at $1.26$ m from it.

Q: A $-2.0\ \mu\text{C}$ charge and a $+6.0\ \mu\text{C}$ charge are placed $1.0$ m apart. What is the magnitude of the electric field at the midpoint between them?

$E = k \left( \dfrac{6.0 \times 10^{-6}}{0.5^2} - \dfrac{2.0 \times 10^{-6}}{0.5^2} \right)$

Question 1

Which of the following statements correctly describes the difference between gravitational and electrostatic forces?

Accepted Answer

Electrostatic forces can be both attractive and repulsive, while gravitational forces are always attractive.

Question 2

What is the SI unit for measuring electric charge?

Accepted Answer

Coulomb (C)

Question 3

Which particle has the same magnitude of charge as an electron but opposite sign?

Accepted Answer

Proton

Question 4

If an object has a net charge of $q = 4.8 	imes 10^{-19}$ C, how many excess protons does it have?

Accepted Answer

$3$

Question 5

Which process describes the removal or addition of electrons to an atom, resulting in a net charge?

Accepted Answer

Ionization

Question 6

A glass rod is rubbed with silk. What happens to the charges on the rod and the silk?

Accepted Answer

Electrons are transferred from the rod to the silk, making the rod positively charged and the silk negatively charged.

Question 7

Which of the following best describes charge quantization?

Accepted Answer

Charge is always a multiple of the elementary charge $e = 1.6 	imes 10^{-19}$ C.

Question 8

According to Coulomb’s Law, what happens to the electrostatic force between two point charges if the distance between them is halved?

Accepted Answer

The force becomes four times as strong.

Question 9

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

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

Question 10

A neutral sodium atom loses one electron. What is the resulting charge of the ion?

Accepted Answer

$+e$

Question 11

Which of the following materials is an example of an insulator?

Accepted Answer

Glass

Question 12

What is the principle of superposition as applied to electrostatic forces?

Accepted Answer

The net force on a charge is the sum of all individual forces, added as vectors.

Question 13

A point charge $Q$ creates an electric field at a distance $r$. What is the magnitude of the electric field at that point?

Accepted Answer

$E = k \dfrac{Q}{r^2}$

Question 14

If two identical positive point charges are placed at a distance $d$ apart, where is the electric field zero along the line joining them?

Accepted Answer

At infinity.

Question 15

A $5\ \mu	ext{C}$ charge is located at $(0,0)$ and a $-3\ \mu	ext{C}$ charge is at $(0,4)$ cm. What is the direction of the net force on a positive test charge placed at $(0,2)$ cm?

Accepted Answer

Downward along the y-axis.

Question 16

Which statement about charge conservation is correct?

Accepted Answer

Electric charge cannot be created or destroyed; it is always conserved.

Question 17

A $+8\ \mu	ext{C}$ charge and a $+2\ \mu	ext{C}$ charge are separated by $4$ m. At what point along the line joining them is the net electric field zero?

Accepted Answer

Closer to the $+2\ \mu	ext{C}$ charge, at $1.26$ m from it.

Question 18

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

Accepted Answer

The field points toward the charge.

Question 19

A $+10\ \mu	ext{C}$ charge is placed at the center of a square. Where should a second charge be placed so that the net electric field at one corner is zero?

Accepted Answer

At the corner diagonally opposite to the one in question.

Question 20

A $-2.0\ \mu	ext{C}$ charge and a $+6.0\ \mu	ext{C}$ charge are placed $1.0$ m apart. What is the magnitude of the electric field at the midpoint between them?

Accepted Answer

$E = k \left( \dfrac{6.0 	imes 10^{-6}}{0.5^2} - \dfrac{2.0 	imes 10^{-6}}{0.5^2} ight)$

Electricity and Magnetism: Fundamental Properties, Charge, and Electrostatics (Chapter 22 Study Notes)

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