Conceptual Physics - Chapter 32: Electrostatics

Front 1

The charge of an electron is

Back 1

negative

Front 2

Atomic nuclei of almost all elements consist of

Back 2

protons and neutrons

Front 3

Two like charges

Back 3

repel each other

Front 4

Protons and electrons

Back 4

attract each other

Front 5

The fundamental force underlying all chemical reactions is

Back 5

electrical

Front 6

Electrical forces between charges are strongest when the charges are

Back 6

close together

Front 7

Coulomb's law says that the force between any two charges depends

Back 7

• directly on the size of the charges

• inversely on the square of the distance between the charges

(A and B)

Front 8

Two charges are separated by a certain distance. If the magnitude of each charge is doubled, the force on each charge is

Back 8

quadrupled

Front 9

When the distance between two charges is halved, the electrical force between the charges

Back 9

quadruples

Front 10

The net charge of a nonionized atom

Back 10

is zero

Front 11

A positive ion has

Back 11

more protons than electrons

Front 12

Conservation of charge means that

Back 12

• the total amount of charge in the universe is constant

• no experimentalist has even seen a single charge destroyed by itself

• electrons by themselves can be neither created nor destroyed

• charge can be neither created nor destroyed

(all of the above)

Front 13

If you comb your hair and the comb becomes positively charged, your hair becomes

Back 13

negatively charged

Front 14

To say that electrical charge is conserved means that no case has ever been found where

Back 14

net charge has been created or destroyed

Front 15

A difference between electrical forces and gravitational forces is that electrical forces include

Back 15

repulsive interactions

Front 16

The common hydrogen atom consists of

Back 16

one proton and one electron

Front 17

In a good insulator, electrons are usually

Back 17

tightly bound in place

Front 18

Objects can be charged by

Back 18

• induction

• friction

• touching

(all of the above)

Front 19

Charge carriers in a metal are electrons rather than protons, because electrons are

Back 19

• relatively far from a nucleus

• loosely bound

• lighter

(all of the above)

Front 20

To be safe in the unlikely case of a lightning strike, it is best to be inside a building frame with

Back 20

steel

Front 21

A conductor differs from an insulator in that a conductor has

Back 21

• NOT more protons than electrons

• NOT faster-moving molecules

• NOT more electrons than protons

• NOT more electrons than an insulator

(NONE of the above)

Front 22

Much electronic equipment contains transistors and diodes that are made from semiconductors.

Semiconductors

Back 22

• can be very good insulators

• can conduct electricity

• contain helpful impurities

(all of the above)

Front 23

A negatively charged rod is brought near a metal can that rests on a wood table. You touch the opposite side of the can momentarily with your finger. The can is then

Back 23

positively charged

Front 24

An electroscope is charged positively, as shown by foil leaves that stand apart. As a negatively charged rod is brought close to the electroscope, the leaves

Back 24

move closer together

Front 25

Lighting bolts occur between

Back 25

clouds and the ground

clouds

(both A & B)

Front 26

To charge an object by induction, the process of grounding

Back 26

may or may not occur

Front 27

When a charged cloud passes overhead, the ground below is charged by

Back 27

induction

Front 28

Bring a charged object near a conductor and then momentarily touch the conductor. This demonstrates charge by

Back 28

induction

Front 29

A rubbed balloon will stick to a wooden wall, which demonstrates charge

Back 29

polarization

Front 30

Electrical polarization occurs when

Back 30

charge distribution in a neutral molecule separates

Front 31

The reason a charged balloon will stick to a wall is that

Back 31

induced opposite charges in the wall are closer than other wall charges

Front 32

The charge distribution in some molecules is permanently separated into positive and negative regions. Such molecules are called

Back 32

electric dipoles

Front 33

Two charged particles held close to each other are released. As they move, the force on each particle increases. Therefore, the particles have

Back 33

opposite signs

Front 34

Two charged particles held close to each other are released. As the particles move, the velocity of each increases. Therefore, the particles have

Back 34

charges that cannot be determined

Front 35

A positive charge and a negative charge held near each other are released. As they move, the force on each particle

Back 35

increases

Front 36

Two charged particles held near each other are released. As they move, the acceleration of each decreases. Therefore, the particles have

Back 36

the same sign

Front 37

How many different kinds of force would act on a proton placed in both an electric field and a gravitational field

Back 37

two

Front 38

The SI unit of charge is the

Back 38

coulomb

Front 39

Particle A has twice as much charge as particle B. Compared to the force on particle A, the force on particle B is

Back 39

the same

Front 40

The electrostatic force between two charges located 8 meters apart is 0.10 N. What will the force be between these charges when they are located 2 meters apart

Back 40

1.6 N

Front 41

A 2-C charge and a 4-C charge attract each other with 10 N of force. How much will a 2-C charge and a 12-C charge attract each other when placed the same distance apart

Back 41

30 N

Front 42

Two charges separated a distance of 1.0 meter exert a 2.0-N force on each other. If the charges are pushed to a separation of 1/3 meter, the force on each charge will be

Back 42

18.0 N

Front 43

Two charges separated by a distance of 1 meter exert a 20-N force on each other. If the charges are pulled to a 2 meter separation distance, the force on each charge will be

Back 43

5.0 N

Front 44

Two charges separated by a distance of 1 meter exert a 2-N force on each other. If the magnitude of each charge is doubled, the force on each charge will be

Back 44

8.0 N

Front 45

The study of electricity at rest is electrostatics

Back 45

true

Front 46

Electrical forces are strong, but in comparison, gravitational forces are stronger

Back 46

false

Front 47

The reason electrons are attracted to protons is that electrons and protons have the same amount of charge

Back 47

false

Front 48

All electrons are identical; all have exactly the same mass and charge

Back 48

true

Front 49

The total amount of charge in the universe is constant. We have never observed a case of net creation or destruction of charge.

Back 49

true

Front 50

Coulomb's law says that the are two kinds of charges, positive and negative

Back 50

false

Front 51

Coulomb's law for electrical charges has the same mathematical form as Newton's law of gravitation

Back 51

true

Front 52

A material is a good insulator if outer electrons of atoms in the material are free to roam around

Back 52

false

Front 53

A material that is a good insulator of electricity is normally a poor conductor of electricity

Back 53

true

Front 54

Semiconductors can be made to conduct electricity and they can also be made to act like good insulators

Back 54

true

Front 55

When an object is charged by contact, electrons flow from the ground onto the object, or from the object onto the ground

Back 55

false

Front 56

When we allow charges to move onto or off a conductor by touching it with something connected to Earth, it is common to say that we are grounding it

Back 56

true

Front 57

A bolt of lightning is a result of charging by induction

Back 57

true

Front 58

An atom that is electrically polarized vibrates in only one direction

Back 58

false

Front 59

State Coulomb's law. Explain what each symbol in it stands for, and use it to find the force bewteen a 0.002-C charge and a 0.006-C charge that are 10 meters apart

Back 59

The force between two charges depends directly on the magnitude of each charge and inversely on the square of the distance between the charges. [eq1] k is the proportionality constant, q₁ and q₂ are the magnitudes of the charges, d is the distance between the charges, and F is the force between the charges. [eq2]

Front 60

List the similarities and differences between Coulomb's law and Newton's law of gravitation

Back 60

Both laws are inverse-square laws and both are directly dependent on the quantities involved; electric charge for electrical force and mass for gravitational force. The Coulomb force is about 1039 times stronger than the gravitational force. Also, the electrical force may be either attractive or repulsive.

Front 61

Calculate the electrical force between two electrons that are located on opposite sides of an ionized hydrogen atom. Use the following values for the distance and charge size.

distance = 5.3 x 10⁻¹¹ m

electron charge = -1.6 x 10⁻¹⁹ C

Back 61

= 8.2 x 10⁻⁸ N

Front 62

What is the difference between an insulator and a conductor? which would you guess copper is? Wood? Distilled water?

Back 62

A good electrical conductor is any material composed of atoms with "loose" outer electrons that are freeto move about in the material, such as copper. A good electrical insulator is a material composed of atoms that tightly bind electrons. Wood and distilled water are examples of good electrical insulators.

Front 63

Why should you not stand or sit in water when using electrical appliances? Why is it not a good idea to talk to your friend on the phone while sitting in a bath?

Back 63

Ordinary water is a conductor of current. Therefore, when using a plugged-in electrical device, you shouldnot be standing or sitting in water that is connected to Earth. If a short circuit occurs, you may be part ofthe pathway to the ground. For the same reason it is not a good idea to use the phone while taking a bath(although the voltage and current in a phone are relatively low).

Front 64

What are three ways an object can become charged? How does each work? Give examples

Back 64

Objects can become charged by friction, contact or induction.

1. In charging by friction, two objects are rubbed together, thereby transferring electrons from one object to the other.
2. In charging by contact charge is also directly transferred from one object to another object. In charging by induction, one objects momentarily grounded while a charged object is located nearby. Rubbing a rubber rod with cat's fur is an example of charging by friction. Touching the charged rubber rod to an uncharged tin can is an example of charging by contact.
3. Holding a charged rod near a tin can and touching the can with your finger is an example of charging by induction.