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Preparation for Physics Final > Chapter 32 > Flashcards

Chapter 32 Flashcards

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1
Q

What is electrostatics?

A

Electricity at rest

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2
Q

Where do electrical forces arise from?

A

Particles in atoms

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3
Q

Who illustrated a simple model of the atom propsed in the 1900s about a positively charged nucleus surrounded by electrons?

A

Ernest Rutherford and Niels Bohr

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4
Q

What do the protons in the nucleus do to the electrons?

A

Attract electrons and hold them in orbit

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5
Q

Electrons are…

A

Attracted to protons but repel other electrons

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6
Q

What is charge?

A

The fundamental electrical property to which the mutual attractions ot repulsiosns between electrons or protons is attributed.

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7
Q

Electons are _________charged

A

negatively

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8
Q

Protons are __________charged

A

positively

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9
Q

Neutrons have _______charge and….

A

No; are neither attracted nor repelled by charged particles

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10
Q

Facts about atoms

A

1). Every atom has a positively charged nucleus surrounded by negatively charged electrons
2). All electrons are identical; that is, each has the same mass and the same quantity of negative charged as every other electron
3). The nucleus is omposed of protons and neutrons (except for for hydrogen which has no neutrons). All protons are identical. All neutrons are identical. A proton has nearly 2000 times the mass of an electron, but its positive charge is equal in magnitude to the negative charge pf an electron. A neutron has slightly greater mass than a protons and has no charge.
4). Atoms have as many electrons as protons, so a neutral atom has zero net charge.

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11
Q

The fundamental rule at the base of all electrical phenomena is…

A

that like charges repel and opposite charges attract

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12
Q

How was the term “opposites attract” orginally coined?

A

By public lecturers who traveled abput by horse and wagon to entertain people by demonstratinf the scientifc marvels of electricity.

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13
Q

Examples of opposites attract

A

Charging and discharging pith balls.
- Pith, a light spongy plant tissue, were coated with aluminium paint so their surfaces would conduct electricity. When suspended from a silk thread, such a ball would be attracted to a rubber rod just rubbed with cat’s fur but then the two made contact, the force of attraction would change to a force of repulsion. The ball would be repelled by the rubber rod but attracted to a glass rod that had just been rubbed with silk.

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14
Q

Nature provides how many kinds of charges?

A

two

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15
Q

What type of charge do electrons and protons have?

A

Electric

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16
Q

In a neutral atom, there are…

A

as many electrons as protons

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17
Q

In a neutral atom, what is the net charge?

A

There is none. The total positive charge balances the total negative chargeexactly.

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18
Q

If an electron is removed from from a neutral atom, what happens?

A

The atom is no longer neutral.

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19
Q

If the atom has one more positive charge (proton) than negatively charge then what is it called?

A

Positively charged

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20
Q

What is a charged atom called?

A

An ion

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21
Q

How is a positive ion made?

A

It is has a net positive charge and has lost one or more electrons

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22
Q

How is a negative ion made?

A

It has a net negative charge, it has gained one or more electrons.

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23
Q

What is matter made put of?

A

Out of atoms

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24
Q

What are atoms made out of?

A

Electrons, Protons, and Neutrons

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25
How does an imbalance happen?
Adding or removing electrons
26
The innermost electrons in an atom are bound...
Very tightly to the oppositely charged atomic nucleus
27
The outermost electrons of many atoms are...
Very loosely and can be easily dislodged
28
What does the amount of energy that is required to tear an elecrron away from an atom depend on?
On the differnt substance
29
Electrons are held more firmly in fur than rubber. T or F/
False Example). Electrons transfer from the fur to the rubber rod. The rubber then has an excess of electrons and is negatively charged. THe fur, in turn, has a deficiency of electrons and is positively charged.
30
If you rub a glass of plastic rod with silk, what happens? Why?
The rod becomes positively charged. The silk has a greater affinity for electrons than the glass or plastic rod. Electrons are rubbed off the rod and onton the silk.
31
An object that has unequal numbers of electrons and protons is...
electrically charged
32
What does the principle of conservation of charge state?
ELectrons are neither created nor destroyed but are simply transferred from one material to another.
33
Does the principle of conservation of charge apply to every event, whether large-scale or at the atomic and nuclear level?
Yes
34
A case of the creation or destruction of net electric charge has been found. T or F
False
35
Any object that is electrically charged has an ________or _________ of some whole number of _________.
excess; deficiency; electrons
36
Can electrons be divided into fractions of electrons?
No
37
What does it mean when we state that electrons cannot be divided into fractions of electrons?
That the charge of the object is a whole-number multiple of the charge of an electron.
38
The electrical force between any two objects obeys...
A similar inverse-square relationship with distane
39
What is Coulomb's law?
The relationship among electrical force, charges, and distances, discovered by French physicist Charles Coulomb (17-36-1806) in the 18th century
40
Coulomb'a law states that for __________ particles or objects that are _______compared with the _________between them, the ________between the _______varies ________as the product of the _________and ________as the square of the ________between them.
charged; small; distance; force; charges; directly; charges; inversely; distance.
41
What is the SI unit of charge?
Coulomb (C)
42
What is the charge of 1C?
6.24 billion billion( 6.24 x 10^18) electrons
43
How much does 6.24 billion billion( 6.24 x 10^18) electrons power?
A 100-W lightbulb i about 1 sec
44
The proportionality constand k in Coulomb is similar to...
G in Newton's law of gravity
45
Is it always true that electrical forces balance out for astronomical and everyday objects?
No
46
What often happens when two or more atoms are close together?
They share electrons
47
The negative electrons of one atom may at times...
Be closer to the neighboring atom's positive nucleus than they are to the average location of the neighbors electrons. Then the attractive force between these charges is greater than the repulsive force.
48
Are electrons more easily moved in some materials than others?
Yes
49
What is unique about the outer electrons of the atoms?
They are not anchored to the nuclei of particular atoms, but are free to roam in the material
50
What are concuctors?
Materials through which electric charge can flow
51
Why are metals good conductors for the motion of electric charges and heat?
Their electrons are "loose"
52
How do the electrons in rubber and glass act?
Their electrons are tightly bound and remain with particular atoms. They are not free to wander about to other atoms in the material.
53
What are Insulators?
Poor conductors of electricity and heat
54
What does whether a substance is classified as a conductor or an insulator depend on?
How tightly the atoms of the substance hold their electrons
55
Electrons move ______in good ___________and _____in good _____________.
easily; conductors; poor; insulator
56
How can all substances be arranged?
In order of their ability to conduct electric charges. The conductors are at the top of the list and the insulators at the bottom of the list.
57
How much bigger is the conductivity of a metal than glass?
A million trillion times greater.
58
How will charges flow in a common household appliance cord?
Charges will flow through several meters of wire to the aplliance, and then through its electrival network, and then back through the return wire rather than flow directly across from one wire to the other through the tiny thickness of rubber insulation.
59
Can some materials, like germanium and silicon, be good insulators in their pure crystalline form but increase tremendously in conductivity when even one atom in ten million is replaced with an impurity that adds or removes an electron from the crystal struture?
Yes
60
What are semiconductors?
Materials that can be made to behave sometimes as insulators and sometimes conductors
61
Atoms is a semiconductor...
Hold their electrons until given small energy boosts. This occurs in photovoltaic cells that convert solar energy into electrical energy.
62
What makes up transistors?
Thin layers of semiconducting materials sandwiched
63
What do transistors ampilfy?
Electric signals and act as electric switches to control current in circuits - with very little power.
64
What are two ways that electric charge can be transferred?
Friction and by contact
65
What happens when we stroke a cat's fur and hear the crackle of sparks and more?
Electrons are being transferred by friction when one material rubs against another.
66
What happens when a charged rod is palced in contact with a neutral object?
Some charge will transfer to the neutral object, charging by contact.
67
Through, charging by contact, if the object is a good conductor..........
The charge will spread to all parts of its surface b/c the like charges repel each other
68
Through, charging by contact, if the object is a poor conductor..........
The extra charge will stay close to where the object was touched
69
If a charged object is brought near a conducting surface, even w/o physical contact...
Electrons will move in the conducting surface
70
If the uncharged insulated metal spheres touch each other...
they form a single noncharged conductor.
71
If a negatively charged rod is held near a sphere...
Electrons in the metal are repelled by the rod, and excess negative charge has moved on to another sphere, leaving the first sphere with excess positive charge
72
Induced
The charge on the two spheres has been redisturbed
73
Induction
The charging of an object w/o direct contact
74
Charges that repel each other...
Have a conducting path to a practically infinite reservoir for electric charge - the ground
75
Grounding
When we allow charges to move off (or onto) a condutor by touching it
76
How does charging by induction occur during thunderstorms?
The negatively charged bottoms of clouds induce a positive charge on the surface of Earth below. Benjamin Franklin was the first to demonstrate this in his famous kite-flying experiement.
77
What did Franklin discover?
That charge flows more readily to ot from sharp points.
78
What did Franklin invent?
The first lightning rod
79
If the lightning rod is placed above a building connected to the ground...
The point of the rod collects electrons from the air, preventing a large buildup positive charge on the building by induction.
80
What is the primary purpose of the lightning rod?
To prevent a lightning discharge from occuring.
81
Is charging by induction restricted to conductors?
No
82
Charge polarization can occur in...
insulators that are near a charged object
83
When a charged rod is brought near an insulator...
There are no free electrons to migrate throughout the insulating material. There is a rearrangement of the positions of charges within the atoms and molecules themselves
84
What does it mean when we say an atom or molecule is electrically polarized?
One side of the atom or molecule is induced to be slightly more positive or negative than the opposite side.
85
If the charged rod is negative then...
The positive side of the atom or molecule is toward the rod and the negative side of the atom or molecule is away from it.
86
What does an object that clings to the charged object ans suddenly flies off indicate?
That charging by contact has occurred.
87
If you rub a balloon on your arm and stick on the wall, what does that indicate?
The charge on the balloon induces an opposite surface charge on the wall. The charge on the balloon is slightly closer to the opposite induced charge than to the charge of the same sign.
88
Many molecules are...
Electrically polarized in their normal states. For example, H2O. The distribution of electric charge is not perfectly even.
89
Electric dipoles
There is a little more negative charge on one side of the molecule on the other.
90
What are three ways objects are electrically charged?
1). By friction, when electrons are transferred by friction from one object to another. 2). By contact, when electrons are transferred from one object to another by direct contact without rubbing. A charged rod placed in contact with an uncharged piece of metal, for example, will transfer charge to the metal. 3). By induction, when electrons are cause to gather or disperse by the prescence of nearby charge (even without physical contact). A charged rod held near a metal surface, for example, repels charges of the same sign as those on the rod and attracts opposite charges. The result is a redistribution of charge on the object without any change in its net charge. If the metal surface is discahrged by contact, with a finger for example, then a net charge will be left.
91
What happens to the three ways objects are electrically charged when the object is an insulator...
Then a realignment os charge rather then a migration of charge occurs.

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