CHAPTER 22

Question 1

Two isolated charges repel each other when approached. What can we say about these charges?

Answer 1

They have the same type of charge.

Question 2

How do you compare the charge of the
electron versus the charge of the proton?

Answer 2

The same magnitude, but opposite signs.

Question 3

Most atoms normally have a net charge
that is _________.

Answer 3

zero

Question 4

Which part of an atom is positively
charged, and which part is negatively
charged?

Answer 4

The nucleus is positively charged and the electron cloud is negatively charged.

Question 5

What is the most common net charge of
an atom?

Answer 5

Neutral

Question 6

When we say charge is conserved,
we mainly mean that charge can be
_________.

Answer 6

transferred without loss like money in a bank

Question 7

After two objects were briefy in contact,
it is determined that one of them has
n electrons in excess. What can you say
about the charge of the second object?
(There may be more than one right answer.)
Check all that apply.
A. It is missing n electrons.
B. It is less charged.
C. It is more charged.
D. It has n protons in excess.

Answer 7

It is missing n electrons, It has n protons in excess.

Question 8

What is a positive ion? What is a negative
ion?

Answer 8

A positive ion is a neutral atom that has lost one or more electrons. A negative ion is a neutral atom that has gained one or more electrons.

Question 9

What is meant by conservation of
charge?

Answer 9

Net charge cannot be created or destroyed.

Question 10

What would happen to the two balls if
one of them were kept positively charged
and the charge on the other ball were
slowly increased, making it more and
more positive?

Answer 10

The balls would begin to move farther apart.

Question 11

What would happen to the two balls if
one of them were kept positively charged
and the charge on the other ball were
slowly made increasingly negative?

Answer 11

The balls would begin to move closer together.

Question 12

What would happen to the two balls if
both of them had a non-neutral charge
and you slowly increased the mass

Answer 12

The angle of the balls with respect to the vertical would decrease.

Question 13

Coulomb’s law is most similar to which of
these laws or definitions?

Answer 13

Newton’s law of gravity

Question 14

What happens to the force between two
charges if they are moved to three times
the distance?

Answer 14

The force decreases nine times.

Question 15

How does one coulomb of charge compare with the charge of a single electron?

Answer 15

A coulomb of charge is the charge associated
with 6.25 × 10^18 electrons.

Question 16

How is Coulomb’s law similar to Newton’s
law of gravitation? How is it different?

Answer 16

Newton’s law of gravitation is attractive, whereas Coulomb’s law is attractive or repulsive. Both are proportional to the inverse square of distance.

Question 17

Why are metals good conductors of both
heat and electricity?

Answer 17

The outer shell electrons in metals are free to
move from atom to atom.

Question 18

Why are materials such as glass and rubber good insulators?

Answer 18

Electrons are tightly bound to their atoms,
making them poor conductors of heat.

Question 19

How does a semiconductor differ from a
conductor or an insulator?

Answer 19

A semiconductor is neither a good conductor
nor a good insulator - it has a middle range of
resistivity.

Question 20

What is a transistor composed of, and
what are some of its functions?

Answer 20

A transistor is made of thin layers of semiconducting materials sandwiched together. It can be a switch, an oscillator, or an amplifier.

Question 21

How does the flow of current differ in a
superconductor compared with the flow
in ordinary conductors?

Answer 21

Superconductors have infinite conductivity
(current flows forever), whereas ordinary conductors have a small resistance to the flow of electric charge.

Question 22

The large positive charge inside the shell
causes equal in magnitude charges distributed on the inner and outer surfaces
of the spherical shell. Which of the pictures best represents the charge distribution on the inner and outer walls of the
shell?
A. 1
B. 2
C. 3
D. 4
E. 5

Answer 22

4

Question 23

The large positive charge inside the shell
causes equal in magnitude charges distributed on the inner and outer surfaces
of the spherical shell. Which of the following fgures best represents the charge
distribution on the inner and outer walls
of the shell?
A. 1
B. 2
C. 3
D. 4
E. 5

Answer 23

1

Question 24

Which of the figures best represents the
charge distribution on the inner and outer walls of the conductor?
A. 1
B. 2
C. 3

Answer 24

3

Question 25

Electric charge can be transferred from one conducting body to another _________.

Answer 25

by both contact and closeness

Question 26

What happens to electrons in any charging process?

Answer 26

Electrons transfer from one place to another.

Question 27

What kind of charging occurs when you slide your body across a plastic surface?

Answer 27

Charging by friction occurs. Electrons are transferred when one object rubs against another.

Question 28

What kind of charging occurs during thunderstorms?

Answer 28

Ice crystals are charged by friction and the ground is charged by induction.

Question 29

What is the primary purpose of a lightning rod?

Answer 29

To prevent a fire caused by lightning

Question 30

The net charge on a polarized molecule is normally _________.

Answer 30

zero

Question 31

In terms of net charge, how does an electrically polarized object differ from an electrically charged object?

Answer 31

An electrically polarized object can have zero net charge, while a charged object cannot have zero net charge.

Question 32

What is an electric dipole?

Answer 32

In an electric dipole, positive and negative charges are separated on opposite sides of an object.

Question 33

Which molecule is an example of a common electric dipole?

Answer 33

A water molecule

Question 34

An electric field is ___________.

Answer 34

a vector quantity

Question 35

How is the direction of an electric field defined?

Answer 35

The direction of the field is the direction of the force on a positive test charge.

Question 36

Why is there no electric field at the center of a charged spherical metal ball?

Answer 36

Because of mutual repulsion, mobile electrons in the conductor will spread out uniformly over the outer surface of the ball, so the force and the field on a test charge at the center is zero because opposing forces balance in every direction.

Question 37

When charges mutually repel and distribute themselves on the surface of conductors, what becomes of the electric field inside the conductor?

Answer 37

The charges arrange themselves to make the field inside the conductor zero.

Question 38

Electric potential, unlike electric potential energy, is measured in units of _________.

Answer 38

volts

Question 39

A highly charged party balloon is not dangerous when it _________.

Answer 39

contains little overall energy

Question 40

The net charge on an energized capacitor is normally _________.

Answer 40

zero

Question 41

The electric field inside the dome of a highly charged Van de Graaf generator is _________.

Answer 41

zero

Question 42

When is a capacitor fully charged?

Answer 42

When voltage between the plates and the potential difference between the battery terminals have equalized

Question 43

A balloon may easily be charged to several thousand volts. Does that mean it has several thousand joules of energy? Explain.

Answer 43

No. Energy is voltage times charge, so you need a coulomb of charge to get several thousand joules of energy.

Question 44

Where is the energy stored in a capacitor?

Answer 44

The energy is stored in the electric field between the plates.