Q: A neutral lithium atom has 3 protons, 4 neutrons, and 3 electrons. If it loses one electron, what is the net charge of the resulting ion?

$$+1.602 \times 10$$^{-19}$$\ \mathrm{C}$$

Question 1

Which of the following statements best describes the principle of charge conservation?

Accepted Answer

The algebraic sum of all electric charges in any closed system is constant.

Question 2

A neutral lithium atom has 3 protons, 4 neutrons, and 3 electrons. If it loses one electron, what is the net charge of the resulting ion?

Accepted Answer

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

Question 3

Which material would best serve as an insulator in an electrical circuit?

Accepted Answer

Glass

Question 4

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

Accepted Answer

The force decreases by a factor of 4.

Question 5

A point charge $$q = -8\ \mathrm{nC} is $$located at the origin. What is the direction of the electric field at the point $$(1.2, -1.6)$$ meters?

Accepted Answer

Toward the origin

Question 6

Which of the following equations correctly expresses the magnitude of the electric force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

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

Question 7

A small object of mass $$3.80\ \mathrm{g}$$ and charge $$-18.0\ \mu\mathrm{C} is $$suspended motionless above the ground in a uniform electric field. What is the magnitude of the electric field required to balance the weight of the object?

Accepted Answer

$$E = \frac{mg}{|q|}$$

Question 8

Which of the following best describes the behavior of electric field lines for a positive point charge?

Accepted Answer

They radiate outward from the charge.

Question 9

If two identical positive charges are placed at the vertices of an equilateral triangle and a negative charge of equal magnitude is placed at the third vertex, what is the direction of the net electric force on one of the positive charges?

Accepted Answer

Away from the other positive charge and toward the negative charge

Question 10

A laser printer uses the principles of electrostatics to operate. Which of the following best explains how it works?

Accepted Answer

It uses the attraction and repulsion between charged particles to transfer toner to paper.

Question 11

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

Accepted Answer

Charges move freely in conductors but not in insulators.

Question 12

A charged rod is brought near a neutral metal ball, causing the ball to become charged without direct contact. What is this process called?

Accepted Answer

Charging by induction

Question 13

Which of the following is the correct expression for the electric field $$E at a $$distance $$r$$ from a point charge $$Q$$?

Accepted Answer

$$E = \frac{1}{4\pi\$$varepsilon_0$$} \frac{|Q|}{r^2$}$$

Question 14

A water molecule is an example of which of the following?

Accepted Answer

An electric dipole

Question 15

Which of the following best describes the direction of the force on a negative test charge placed in an electric field?

Accepted Answer

Opposite to the direction of the electric field

Question 16

If the product $$q_1$$ $$q_2 in $$Coulomb’s law is negative, what can be said about the force between the two charges?

Accepted Answer

The force is attractive.

Question 17

A thin stream of water bends toward a negatively charged rod. What will happen if a positively charged rod is placed near the stream?

Accepted Answer

It will bend in the same direction.

Question 18

Which of the following is the correct formula for the torque $$	au on an $$electric dipole $$\vec{p} in a $$uniform electric field $$\vec{E}$$?

Accepted Answer

$$	au = \vec{p} 	imes \vec{E}$$

Question 19

Which of the following is NOT a rule for drawing electric field lines?

Accepted Answer

Field lines can cross each other.

Electric Charge and Electric Field: Fundamental Concepts and Applications

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