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The final mock (Physics) > Unit 4.2 Electrostatic Fields (No escape velocity & distance approach) > Flashcards

Unit 4.2 Electrostatic Fields (No escape velocity & distance approach) Flashcards

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1
Q

What does electrostatically charging an object involve?

A

Redistribution, addition or removal of electrons

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2
Q

What are the 2 ways to charge and object?

A
  • Charging by friction
  • Charging by induction
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3
Q

What is charging by friction?
(4-way)

A
  • Process of friction generates energy
  • … to remove some electrons from the surface
  • … of the material and place them
  • … onto the duster
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4
Q

What is charging by induction?
(2-way + 2-way)

A
  • Electrons redistribute themselves on the leaves
  • … of the electroscope
  • Positive charge induced on the
  • … top plate of the electroscope
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5
Q

Examples of everyday charging?
(Just know that one)

A
  • Lightning clouds
  • Hair n stuff
  • Christmas jumper
  • Comb??
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6
Q

What is the 2 principles of electrostatics?

A
  • Like charges repel
  • Unlike charges attract
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7
Q

Show me like charges repel?
(2 light things)

A
  • Positive to a positive repel
  • Negative to a negative repel
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8
Q

Show me unlike charges attract?

A

Positive to a negative attract each other

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9
Q

Define induction in general?

A

When it’s not touching

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10
Q

Define conduction in general?

A

When it’s touching

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11
Q

Explain gold-leaf electroscope

A

Later

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12
Q

Explain electric field lines for a positive point charge?

A

Arrows directed away from center

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13
Q

Explain electric field lines for a negative point charge?

A

Arrows directed towards the center

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14
Q

What would u see for electric field lines if there’s a positive point charge near a negative point charge?
(2-way + 3-way)

A
  • Arrows from positive point charge
  • directed towards negative point charge
  • The direction of the arrows some are straight
  • Others are curved
  • Based on closeness
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15
Q

How would u increase electric field lines curve strength?
(2 things)

A
  • Decrease distance
  • Increase quantity of point charges
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16
Q

Diagram of field between 2 parallel plates?

A

Whiteboard if u need it

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17
Q

Explain electric field between 2 oppositely charged parallel plates?
(1 + 2-way + 1 thing)

A
  • Field lines = straight & parallel to one another
  • ∴ field’s strength uniform throughout
  • … except edges
  • At edges = field strength slightly less
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18
Q

What happens to the field if u increase the quantity?
(2 comparisons)

A
  • Magnitude doubles if u add 1 (+2Q)
  • Magnitude triples if u add 2 (+3Q)
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19
Q

What would happen to the field for ‘unlike point charge’
(Field between two point charges)
(2 things)

A
  • Attraction
  • Basically looks like magnet directions/arrows
    (u should probably draw it)
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20
Q

What would happen to the field for ‘like point charge’
(Field between two point charges)
(2 things + 2-way)

A
  • Repel
  • Similarities for less curves
  • Likewise to negative version
  • …. but arrows towards negative
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21
Q

What’s the jig with field for ‘like point charge’?
(1 thing + 3-way)

A
  • It has a point where the field is zero
  • Due to vector lines at these points…
  • are equal and in opposite direction
  • ∴ they cancel out
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22
Q

Diagram for the field ‘like point charge’
(Field between two point charges)

A

Whiteboard

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23
Q

What does the density of field lines indicate?

A

Its relative strength of the field

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24
Q

What does the direction of the field line indicate?
(3-way)

A
  • Direction of the force
  • experienced by a small positive charge
  • placed in that position
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25
Q

How do u calculate the strength of a charges’ (Q) field (E)?
(2-way + 1 way?)

A
  • Place a positive test charge q
  • in the field
  • Measure force acting on it
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26
Q

Electric field strength equation?
(Analogous to capacitance version O_o)
(NOT IN DATA BOOKLET)

A

E = f/q

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27
Q

Define E
(Electric field strength equation)

A

… The electric field strength
(NC-1)

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28
Q

Define f
(Electric field strength equation)

A

Force
(N ig?)

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29
Q

Define q
(Electric field strength equation)

A

Charge
(C)

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30
Q

Electric field strength equation expressed in words?

A

Electric field strength = Force/Charge

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31
Q

Definition of the electrical field strength?

A

Force per unit charge

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32
Q

The 2 different units for E (electrical field strength)?

A
  • NC-1
  • Vm-1 (E = v/d, capacitance version)
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33
Q

The 2 things to note for electrical field strength equation + positive test charge?
(Lil check up)

A
  • Magnitude of the field strength at any point in the field is independent of the test charge
  • The direction of the field depends upon the charge of Q which generates the field; however, a positive test charge must always be sued to define the direction
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34
Q

What equation for E in a radial field?
(In data booklet)

A

E = (1/4πε0) x Q/r2

35
Q

Define 1/4πε0
(E in a radial field equation)

A

= 9 x 109 Fm-1
A constant…. kind of.

36
Q

What’s the jig with 1/4πε0?

A

k = 1/4πε0 = 9 x 1010

37
Q

Define Q
(E in a radial field equation)

A

Charge
(C)

38
Q

Define r
(E in a radial field equation)

A

Radial distance from point charge
(m)

39
Q

What’s the ε0 known as?

A

Permittivity of free space

40
Q

For E in a radial field, what is the relationship between charge and E?

A

They’re directly proportional
(E ∝ Q)

41
Q

For E in a radial field, what is the relation between distances and E?

A

They’re inversely proportional
(E ∝ 1/r2)

42
Q

What’s the relationship between E and radial distance another example of?

A

The inverse square law

43
Q

If r doubles, what happens to E?
(Relationship between E and r)

A

E becomes 1/4 of its previous strength

44
Q

If r is halved, what happened to E?
(Relationship between E and r)

A

E becomes 4 times greater

45
Q

Combining electric fields using vector addition
(lil check up)

A

I’ll come back to it.
It’s actually a bit similar to basic physics vectors.
Tho obviously, “analogous”

46
Q

Tell me what u know so far for the combining electric fields
(Future self)

A
  • Once again, like resolving vectors
  • Tho apparently mostly u wouldn’t be needed sin + cos
  • (Horizontal & vertical components)
  • Typical equation is E = k x Q/r2
  • k obviously the constant
  • Take in consideration of what happens between + against -
  • or - against - or + against +
  • Don’t forget to square
  • In addition, finding magnitude and direction
  • I’ll stick with this
47
Q

What’s it called for if we consider force experienced by a second charge (q), place in a specific position in some rando’s field

A

Electrical field force (Coulomb’s Law)

48
Q

The typical equation for finding force in an electric field?
(Capacitance type shi)

A

F = E x q

49
Q

Therefore, the equation for the electric field force?
(In data booklet except in k terms)

A

F = k x (Q1Q2)/r2

50
Q

Define F
(Electric field force eqn)

A

Force between charges
(N)

51
Q

Define Q
(Electric field force eqn)

A

Charge
(C)

52
Q

Define k
(Electric field force eqn)

A
  • Constant of proportionality
  • Coulomb’s constant
    (Nm2C-2 aka 1/4πε0)
53
Q

Define r
(Electric field force eqn)

A

Separation of charges
(m)

54
Q

Define ε0
(Electric field force eqn)

A

Permittivity of free space
(Constant)

55
Q

Definition for Coulomb’s law?
(4-way)

A
  • Force between charges is directly proportional…
  • to the product of charges
  • and inversely proportional to
  • … the distance between charges squared
56
Q

What to take in consideration for electric field force eqn?
(2-(way) + 2 things)

A
  • For finding the charge, be aware whether it’s + or -
  • (Rules of magnets n stuff)
  • If attracting, Force = negative
  • If repelling, Force = positive
57
Q

Glad i did that hw asap

A

But now how much can I recall?
+ i forgot what i was gonna say

58
Q

Once again, now u better be sorry

A

…

59
Q

Explanation for the equation for electrical Potential Energy in terms of force/distance graph?
(1, 4-way)

A
  • In a Uniform Field,
  • area under force/distance graph
  • = work done when moving
  • charge through a distance (x)
60
Q

Hence, equation for electrical Potential Energy [in distance]?

A

△W = F △x

61
Q

Definition of potential energy?
(In terms of charge ig)

A
  • The energy required to move
  • the charge from infinity to
  • a point in a field
62
Q

However, what about electrical Potential Energy in a radial field?
(4-way)

A
  • Same principle
  • Area enclosed under…
  • force/radius represents work done
  • when charge moved from r1 to r2 (positions)
63
Q

What does the force/radius graph look like for electrical potential energy in a radial field?

A

A curve

64
Q

In addition, how would u gain the area in the force/radius graph?
(Electrical Potential Energy in a radial field)

A

Count the squares…

65
Q

Thus, the equation of our line for electrical Potential Energy in a radial field?

A

F = k x q1q2/r2

(ofc k = 1/4πε0</sub)

66
Q

BUT ULTIMATELY, the actual equation for the electrical Potential Energy in a radial field?
(In data booklet)

A

PE = Q1Q2/4πε0r

better way for this, k constant.

67
Q

Explain what it means by infinity?
(Electrical Potential Energy in a radial field)
(4-way)

A
  • The zero energy reference but as…
  • Electric Fields,
  • can be attracting/repelling
  • either max. or min. PE
68
Q

What would it mean if the field is attractive?
(Electrical Potential Energy in a radial field)
(4 things)

A
  • Q1Q2 is -‘ve
  • PE = negative
  • Maximum PE at ∞
  • Work to move charge in field is greatest towards ∞
69
Q

What would it mean if the field is repulsive?
(Electrical Potential Energy in a radial field)
(4 things + 1 optional special)

A
  • Q1Q2 is +’ve
  • PE = positive
  • Minimum PE at ∞
  • Work to move charge in field is lowest to ∞
  • Like a spring pushed down…
70
Q

Explain what the electrical potential (VE) due to a point charge is?
(4-way)
(Electrical Potential (VE of a position)

A
  • The work done in…
  • bringing a unit positive charge from
  • infinity to that point
  • in the field
71
Q

Equation for Electric Potential (volt)?
(JC-1)
(Electrical Potential (VE) of a position)

A

V = W/Test q

72
Q

Data booklet edition for equation for Electric Potential (volt)?
(Electrical Potential (VE) of a position)

A

W = q △VE

73
Q

Derive expression for Electrical Potential V using equation for electrical PE in radial field?
(3 by 3 step)
(Electrical Potential (VE) of a position)

A
  • VE = PE/q
  • PE = k x Q1Q2/r
  • Hence, VE = k x Q/r
74
Q

[Useful] way to imagine potential (work done per unit charge)?
(2-way)

A
  • Imagine a “potential surface”
  • created by a point charge
75
Q

Surface of zero potential would be?
(Potential wells and hills)

A

Flat surface

76
Q

Explain the positive charge in terms of…
(Potential wells and hills)
(a thing + 3-way + a things)

A
  • Creates potential “hill”
  • +’ve work done must be done to move
  • a +’ve test charge closer to it
  • “as tho u’re moving it up a hill”
  • +’ve work done when against electric force
77
Q

Explain the negative charge in terms off…
(Potential wells and hills)
(a thing + 3-way + a things)

A
  • Creates a potential “well”
  • -‘ve work done to move…
  • a +’ve test charge closer to it
  • “as tho u’re moving it down a well”
  • -‘ve work done when moving with electric force
78
Q

What’s electrical potential (VE) of a position similar to?
(1 imp + 3-way)

A
  • Like PE of a charge in a field
  • Electrical Potential (VE) of a point in a field is:
  • negative in an attractive field
  • positive in a repulsive field
79
Q

How to find resultant potential at point x if multiple charges is present?
(1 thing but optionals if u want)

A

i.e. Q1, -Q2 Q3
- Algebraic sum of the potentials
- Resultant V at X = V1 - V2</sub< + V3

80
Q

Sketch and label how potential varies with distance for both a positive and negative charge (graph)

A

Stage is yours

81
Q

Gradient for [how potential varies with distance (graph)]?
(3-way)

A
  • Gradient of graph = rise/run = △VE/△r
  • VE = k x Q/r
  • ∴ gradient = k x Q/r2 = E
  • but ultimately, gradient = -E
82
Q

How’s that the gradient for [how potential varies with distance (graph)]?
(4-way)

A
  • Direction given by charge producing field
  • Negative charge producing -E (inwards)
  • Positive charge producing +E (outwards)
  • ∴, gradient = -E
83
Q

It’s like, I forgot I had physics
SO, what’s left?:

A
  • Escape velocity in electrical fields
    (as much as i’d start this first…. it’s already a major sell that I didn’t do the previous work ¬.¬)
84
Q

I have a choice:
- Make notes for escape velocity in electrical fields
- Boycott, start the real revision

A

The final mock (Physics) (7 decks)

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