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Physics Theory > Ch17 Static Electrisity > Flashcards

Ch17 Static Electrisity Flashcards

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1
Q

Define static electricity:

A

Electric charge held by a charged insulator

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2
Q

Define electrostatic charge:

A

A property of an object that causes it to attract/repel other objects with charge

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3
Q

Define positive charge:

A

The type of electric charge carried in the nucleus of an atom

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4
Q

Define negative charge:

A

The type of electric charge carried by electrons

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5
Q

Define neutral:

A

Having no overall positive/negative charge

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6
Q

Define electrical conductor:

A

Is substance that allows the flow of electrons (electric current)

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7
Q

Define electrical insulator:

A

The substance that inhibits the flow of electrons (electric current)

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8
Q

Define electric field:

A

Region of space in which an electric charge will experience a force

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9
Q

Define coulomb (C) :

A

The SI unit for electric charge

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10
Q

Define proton:

A

A positively charged particle found in the atomic nucleus

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11
Q

Define electron charge:

A

The electric charge of a single electron

-1.6 x 10^-19 C

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12
Q

Define proton charge:

A

The electric charge of a single proton
+=1.6 x 10^-19 C

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13
Q

What generates static electricity?

A

Friction

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14
Q

What are the 2 types of static electricity?

A

Positive charge
Negative charge

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15
Q

Give 3 statements about the forces that the electric charges exert on one another:

A

1) 2 positive charges will repel each other
2) 2 negative charges will repel each other
3) a positive and negative charge will attract each other

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16
Q

What is the difference between magnetism and static electricity?

A

Magnetism arises from magnetic poles
Static electricity arises from electric charges

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17
Q

Give 2 characteristics and 1 example of resin:

A

1) good insulator
2) easily becomes electrostatically charged

Ex. Amber (resin from trees that harden and become fossilized)

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18
Q

How does an object obtain an electrostatic charge:

A

→ when an object gains electrons, it becomes negative

→ when an object loses electrons, it becomes positive

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19
Q

Why do you need two different materials to gain static electricity?

A

When two different poorly conducting materials are rubbed together (or even touch) they can each gain an opposite static electric charge. This is because materials differ in how tightly they bind surface electrons.

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20
Q

What happens if you rub ** two of the same materials** together?

A

If you rub two identical materials together, they are both going to gain and lose electrons at the same rate. The net difference in electrons is going to remain zero. There won’t be an imbalance, and you won’t have a static electric charge.

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21
Q

Why don’t metal object stay charged?

A

Metals are electrical conductors, which means electrons can move through them and the metal doesn’t stay charged

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22
Q

Why can charge move through conductors but not through insulators?

A

In insulators, electrons are tightly bound to their atoms
In conductors, some of the electrons are free to move between atoms (free electrons)

Ex. When you rub a polythene rod, gain electrons from the cloth and so becomes negatively charged. The electrons cannot move through the polythene, so the end which was rubbed remains charged
IN CONTRAST
When a copper rod is rubbed electrons are also transferred by friction, but these electrons are free to move, so they flow through the rod, through your hand and into earth. This means that the copper does not become charged.

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23
Q

When can a metal object be charged?

A

When it is held by an insulating handle
In this case, the charge will spread even through the conductor

24
Q

Why can the charged object affect other objects even without touching it?

A

Because there is an electric field around the charged object

25
Q

Are electric electric field lines oming into a positive charge or negative charge?

A

Positive charge

26
Q

What is Coolum named after?

A

Charles-Augustine de Coulomb, a French physicist

27
Q

What does the force between two charged objects depend on?

A

→ how big there charges are
→ how far apart they are

28
Q

How are electrons held to atoms?

A

Electrons, negatively charged, or held on by the attraction of the positively charged nucleus of the atom

29
Q

What is the electron cloud?

A

The space around the nucleus where electrons are likely to be found

30
Q

What does elementary charge (e)?

A

Atomic level unit of charge (charge of electrons and protons)

31
Q

Compare 1 coulomb to elementary charge

A

One coulomb is the total charge carried by 6.25 x 10^18 electrons.

32
Q

What is the physical quantity of of charge represented by?

A

Q or q

33
Q

Compare one in a elementary charge to coulomb:

A

1 e = 1,602 x 10^-19 C

34
Q

What is an atom with a charge called?

A

Ion

35
Q

Define the law of conservation of charge

A

The next quantity of charge produced in any process is zero

During any process, the net charge of the system remains constant

The net charge of the object stays constant in an isolated system

36
Q

How do conductors and insulators influence static electricity?

A

Insulators were materials such as silk or glass that could hold a static electric charge but could not conduct it from place to place, whereas conductors were materials such as metal or water which could not hold a static charge, but did conduct it.

Insulators prevent electrons from moving and the charge remains static, whereas conductors allow the electrons to move through them creating dynamic electricity

37
Q

What materials are good conductors?

A

All the metals
The graphite form of carbon

38
Q

What materials are good insulators?

A

Sulphur
quartz
paraffin wax
PVC
polythene
silk

39
Q

Name not so good insulators:

A

Paper, wool, cotton and wood
Such materials are fibrous and may hold moisture that causes them to conduct a bit
If they are thoroughly dry, they are quite good insulators

40
Q

What is an important requirement for charge to transfer?

A

Contact

41
Q

What does discharging mean?

A

A process when an object loses its net charge

42
Q

What does charging mean?

A

When charge transfers and an object gains net charge

43
Q

Name three ways for charging objects:

A

1) charging by rubbing
2) charging by conduction
3) charging by induction

44
Q

What are the two conditions necessary for charging by rubbing?

A

1) good contact
2) materials must be different

45
Q

How are the electrons removed from their atoms when the two materials are rubbed against each other?

A

No, it is not the energy for rubbing the object against each other that remove the electrons, because it is not nearly enough.

The surfaces of the two objects bond. Molecules of the opposite surfaces bond together through sharing pairs of electrons, one from each side.

46
Q

Give examples of bonding of surfaces:

A

Dress fabric clings to legs
Hard to open new plastic bag
Cling wrap sticks to everything
Plastic sleeve sticks to paper

47
Q

What causes the one material to have more pairs of electrons than the other when they separate after contact?

A

This because the one material had more electronegative molecules that attracted more pairs of electrons than the other because it attracts more strongly and ended up with excess electrons

48
Q

Quick recap: define electronegativity:

A

The measure of an atoms ability to attract shared electrons to itself

49
Q

Does the electronegative surface end up with more negative ions or positive ions?

A

Negative ions, because they contain more electrons

50
Q

Why do you have to rub the two objects together?

A

Some objects have a layer of oil or impurities so simple contact is not effective in bringing two surfaces close enough to to actually touch.
Rubbing them together, enables repeated contact and separation of surfaces

51
Q

What is polarisation?

A

When there is a charge separation in an object.
One side of the object is more positive, and the other end is more negative

52
Q

Describe polarization of a conductor:

A

When is negatively charged object is both near the conductor, the sea of electrons (in the conductor) shift slightly to the far end of the conductor, leaving the end nearest to the negatively charged object with positive charge.

This induces a net positive charge on one end and net negative charge on the far end of the conductor

53
Q

Describe polarization in an insulator:

A

If a negatively charged object is bought near an insulator, the charged object causes charge separation in each molecule of the insulator.
The shape of the molecules in the insulator changes and the end furthest from the negatively charged object is more negative and the nearer the charged object is more positive

54
Q

Define electrostatic equilibrium:

A

When there is no net motion charge within a conductor

55
Q

What is charge induction?

A

A method of charging an object without touching it

56
Q

What is required if you want to charge an object by induction?

A

Earthing

57
Q

What is the phenomenon action-at-a-distance?

A

We charged object exert electric forces on one another without touching

Physics Theory (14 decks)

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