Question 1

Which of the following best explains why lightning occurs during a thunderstorm, as seen in the first image?

Accepted Answer

Lightning is the result of a sudden discharge of static electricity between clouds and the ground, due to the buildup of opposite charges.

Question 2

In the second image, students are touching a metal sphere and their hair stands up. Which principle is best demonstrated here?

Accepted Answer

The students' hair stands up because the metal sphere distributes excess charge over its surface, causing like charges to repel each other.

Question 3

A typical car battery, as shown in the fourth image, is an example of which type of material?

Accepted Answer

Conductor

Question 4

Which equation correctly represents Coulomb’s Law for the force between two point charges?

Accepted Answer

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

Question 5

If two charges are separated by a distance $$d$$ and the force between them is $$F$$, what will the force be if the distance is tripled?

Accepted Answer

$$\frac{1}{9}F$$

Question 6

A sphere of radius $$4.22\ 	ext{cm}$$ and uniform surface charge density $$+12.1\ \mu	ext{C}/	ext{m}^2$$ exerts an electrostatic force of $$46.9 	imes 10$$^{-3}$$\ 	ext{N} on a $$point charge of $$+1.95\ \mu	ext{C}. $$Which formula would you use to find the separation between the point charge and the center of the sphere?

Accepted Answer

$$F = k \frac{Qq}{r^2$}$$

Question 7

Which of the following statements about electric field lines is FALSE?

Accepted Answer

The field is always zero where there are no field lines.

Question 8

A metal ball hangs from the ceiling by an insulating thread and is attracted to a positively charged rod held near it. What must the charge of the ball be?

Accepted Answer

Negative or neutral

Question 9

If a conductor is charged by induction and then grounded, what charge remains on the conductor after the grounding wire and the inducing rod are removed?

Accepted Answer

Positive

Question 10

Which of the following best describes the electric field inside a conductor when charges are at rest?

Accepted Answer

The electric field is zero.

Question 11

A 4 C charge is placed in a uniform electric field and feels a force of 12 N. If a 6 C charge is placed at the same point, what force will it feel?

Accepted Answer

18 N

Question 12

Which of the following is TRUE about the force experienced by a proton and an electron released 1 m apart?

Accepted Answer

Both experience the same magnitude of force.

Question 13

If the electric field at a certain distance from a point charge is $$E_0$$, what is the electric field if both the charge and the distance are doubled?

Accepted Answer

$$\frac{1}{2}E_0$

Question 14

Which of the following best describes the distribution of excess charge on a conductor?

Accepted Answer

Excess charge is distributed over the surface.

Question 15

According to Gauss’s law, what is the total electric flux through a closed surface with no enclosed charge?

Accepted Answer

Zero

Question 16

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

Accepted Answer

Coulomb

Question 17

If two balls with charges +Q and +4Q are separated by 3R, where should you place another charged ball Q0 on the line between the two charges such that the net force on Q0 will be zero?

Accepted Answer

Closer to +Q, at a distance R from +Q and 2R from +4Q.

Question 18

Which of the following materials is most likely to act as a conductor?

Accepted Answer

Copper

Question 19

What happens to the force between a proton and an electron as they move closer together?

Accepted Answer

It gets bigger.

Question 20

Which of the following statements about Gauss’s law is FALSE?

Accepted Answer

All electric field lines are perpendicular to the surface.

Electric Charges, Forces, and Fields (Chapter 19) – Study Notes

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