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Flashcards in Electrostatics Deck (81):
1

What is electricity

name give to a wide range of electrical phenomena

- phenomena associated with the presence and flow of electric charges

2

give 3 examples of electrical phenomena

- lightning
- static electricity
- electrical currents

3

Define electrical force

positive and negative particles are pulled together by the enormous attraction of the electrical force

4

Define electrostatics

branch of physics that deals with phenomena and properties of stationary electric charges

5

Symbol of electric charge

Q

6

Units of electric charge

C; coulombs

7

Define electric charge

Physical property of matter that causes it to experience a force when near other electric charges

8

What are the two types of electric charge

positive
negative

9

true or false; what the charge is called is the result of a choice made by Benjamin Franklin. Could have been the other way around as well

true

10

true or false; mass is always positive

true

11

define elementary charge

the smallest possible unit or charge

12

symbol of elementary charge

e

13

amount of e?

1.602 * 10^-19 C

14

What is the charge of an electron

-e

15

what is the charge of a proton

+e

16

true or false; matter is composed of atoms

true

17

true or false; positively charged nucleus surrounded by negatively charged electrons

true

18

Define the CHARGE of an object

the sum of all the elementary charges contained in the object

19

What is the expression of charge

Q= ne - mp = e(n-m)

20

What does n stand for?

number of protons

21

what does m stand for?

number of electrons

22

Describe a negative charge

more electrons than protons
Qn

23

Describe a positive charge

more protons than electrons
Q>0
n>m

24

true or false; the charge of an electron is equal in magnitude but opposite in sign tot eh charge of a proton

true

25

true or false; like charges repel

true

26

true of false; opposite charges repel

false; they attract

27

What are charged atoms called?

ions

28

What does an object experience when it is charged?

it experiences a force around it

29

true or false; an electrically charged object has an excess or deficiency of some number or electrons

true

30

true or false; a charge must be a whole number multiple of elementary charges

true

31

When is an electron considered not charged/ neutral

when equal amounts of protons and electrons are present

32

what are electrons and protons made of/

quarks

33

State the conservation of charge

Net electric charge can neither be created or destroyed
- electric charge in the universe is conserved

34

true or false; electrons can flow from one object to another but no new electrons are created and no electrons are destroyed

true

35

what does charging mean

a process of moving electrons; transferring electrons from one place to another

36

What does it mean by electric force

force experienced by an ELECTRIC CHARGE when near other electric charges

37

true or false; electric force is some 10^36 times stronger than gravity

true

38

true or false; protons don't move due to their massiveness because they are tightly bound to the nucleus

true

39

What are the 3 types of charging

1.) charging by friction
2. charging by contact
3.) charging by induction

40

What does charging by friction mean?

electrons are transferred by friction when one material rubs against another

41

Define electron affinity

eagerness of a material to take electrons

42

true or false; gravity (mass) is always attractive

true

43

How come when you walk on a wool rug then touch a door knob you feel a mild of electric shock?

this is because the excess electrons you have gathered desperately wants to move from you to the doorknob;
the shock you feel is a result of millions of electrons flowing away from your hand

44

What does charging by contact mean?

electrons are transferred when a charged object touches a neutral object

45

Which of the charges below are possible for an object?
a.) +2e
b.) -2e
c.) +5368 e
d.) -5.368 e

All of them except d, because charges are quantized

46

What does charging by induction mean?

electrons can be moved even without physical contact

47

Give an example of charging by induction

-two neutral objects touching each other
-negative charge brought close to one object
-electrons repelled and wants to get as far away as possible
- now separate the objects, one will be positive and the other one negative
- remove the original charged object, left with two charged objects

48

give an example of charging by friction

rubber is more electrons affinite than animal fur and hence rubbing a balloon on a cat or human hair results in electrons transferring form the cat to the balloon, The balloon becomes negatively charged while the cat becomes positively charged

49

Give an examples of charging by contact

Positive charge attracts electrons from the neutral object; both are positive afterwards (vice versa if negative; both negative afterwards)

50

During a thunderstorm clouds can become charged as pictured below. How will this influence the charge on earth?

this will induce a positive charge onto the Earth due to the negatively charged underside of the cloud

51

What are the 2 forces that govern everything in your life?

electric force
gravitational force

52

true or false; almost all the forces we experience in fay to day life are because of the EM force

true

53

true or false; atoms are 99.99% empty space

true

54

true or false; when we touch a table; the electrons in our hands get closer and closer the electrons of the table and start to repel

true
- nothing ever touches anything (due to repulsion of electric force)
- but the table still feels solid

55

Why don't electrons collapse into the nucleus of an atom?

Electrons are waves rather than particles. In particular, electron waves solve the Schrodigner equation and the solutions tell what is the probability that the electron is some distance from the core. this probability turns out to be zero at the core

56

What does the Schrodinger equation solve?

the probability that the electron is some distance from the core

57

Why don't protons fly out of the nucleus? Shouldn't they repel each other?

strong interactions: short range force that glues protons and neutrons together. Aprrox. 100 times stronger than the electromagnetic force; but only short range

58

What is Coulombs law?

electric force depends on the charges and their separation

59

What is the expression of Coulomb's law?

F = k q1*q2/ d^2
d: separation
q1: charge 1
q2: charge 2
k: constant 9*10^9 Nm^2/C^2

60

what does k stand for in Coulombs law?

9*10^9 Nm^2/C^2

61

What does F stand for in Coulombs law?

electric force

62

how to calculate gravitational force using Coulombs law

F = G m1*m2/d^2
d: separation (m)
m1: mass of object 1
m2: mass of object 2
G: constant 6.7 * 10^-11 m^3/ (kg*s^2)

63

What is the Van de Graaf generator

a device that can store a large static charge

64

why does when touching a Van de Graaf generator ones hair stand up?

charge accumulated on the generator migrates into the person. This makes individual hair strands charged. Because the sign of the charge they posses is identical, they repel each other; they want to get as far away from each other as possible, and to do so they stand up

65

What is an electric field?

property that describes the space surrounding charged particles
- aura surrounding charges particles

66

How can particle 1 push particle 2 since they do not touch?

P1: sets up an electric field
P2: "knows" about particle 1 because it is affected by the electric field set up by particle 1

P1 pushes P2, not by touching ti, but by means of the electric field produced by P1

67

true or false; electric field has a magnitude and a direction

true

68

What does magnitude mean?

force per unit charge.

69

expression of electric field magnitude

E= F/q

70

What are the units of electric field magnitude

N/C = v/m

71

What indicates the direction of magnetic field

arrows (+) ---> (-)

72

What are electric field lines

- a pictorial description of an electric field
- field lines NEVER cross

73

true or false; positive charge moves along the line

true

74

true or false; negative charge moves against the line

true

75

true or false; electric fields can be shielded (blocked) by certain materials whilst gravity cannot

true

76

What shields an electric field?

by a material where electrons are free to move (conductor)
- always so in metals

77

true or false; in electrostatics, the electric field inside a metal object is always zero

true

78

true or false; the electric field inside a conductor is not zero ONLY IF AN ELECTRIC CURRENT FLOWS INSIDE THE OBJECTS

true

79

why does electric shielding occur

the internal electric field exactly cancels the external electric field; test charge would not move anywhere E=0

80

What happens when internal electric field does not equal zero

the free moving electrons would pack to one edge which would raise the internal electric field; continues until the internal electric field exactly cancels the external field; equilibrium

81

What is a faraday cage?

hollow enclosure formed by conducting material or a mesh of such material
- electric shielding possible surrounding an object with conducting material