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ELECTROSTATICS

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ELECTROSTATICS Outline Electric Force, Electric fields Electric Flux and Gaub law Electric potential Capacitors and dielectric (Electric storage) The physics of ... – PowerPoint PPT presentation

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Title: ELECTROSTATICS


1
ELECTROSTATICS
2
Outline
  • Electric Force, Electric fields
  • Electric Flux and Gaub law
  • Electric potential
  • Capacitors and dielectric (Electric storage)

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The physics of charged objects
  • Study of electricity aims to understand the
    interaction between different charged objects.


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The physics of charged objects
  • Study of electricity aims to understand the
    interaction between different charged objects.



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Structure of Matter
  • Fundamental building blocks of the matter are
    atoms.

- electrons
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neutral neutrons
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protons
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Structure of Matter
  • Neutral atom electron Positive ion

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Structure of Matter
  • Fundamental building blocks of the matter are
    atoms.

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Structure of Matter
  • Neutral atom electron negative ion.

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ELECTRICALLY CHARGING OBJECTS

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neutral object
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ELECTRICALLY CHARGING OBJECTS

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positive object
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ELECTRICALLY CHARGING OBJECTS

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negative object
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Charging by Induction
  • In metals outer atomic electrons are not bound to
    any atoms (electron see).











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Charging by Induction
  • In metals outer atomic electrons are not bound to
    any atoms (electron see).


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Charging by Induction
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Electric Polarization
  • Same atoms have weakly bound electrons.

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Electric Polarization
  • Same atoms have weakly bound electrons.

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Electric Polarization
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The Electric Force
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Coulombs Law
  • Quantifies the electric force between two charges.

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Coulombs Law
  • Quantifies the electric force between two charges.

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Coulombs Law
  • Quantifies the electric force between two charges.

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Electric Force Field
  • Gravitational force field

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Electric Force Field
Q
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Electric Force Field
Q
q
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Electric Force Field
  • Definition of Electric field

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Electric Force Field
  • Definition of Electric field

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Electric Force Field





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Electric Force Field
  • The electric field due to a number of source
    charges is given by the expression

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Electric Force Field
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Electric Force Field(Linear distribution of
charge)
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Electric Force Field(Linear distribution of
charge)
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Electric Force Field(Linear distribution of
charge)
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Electric Force Field(Surface distribution of
charge)
da
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Electric Force Field(Surface distribution of
charge)
da
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Electric Force Field(Surface distribution of
charge)
da
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Electric Dipole
  • Electric dipole consists of a pair of point
    charges with equal size but opposite sign
    separated by a distance d.


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Electric Dipole
  • Electric dipole consists of a pair of point
    charges with equal size but opposite sign
    separated by a distance d.


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38
Electric Dipole
  • Electric dipole consists of a pair of point
    charges with equal size but opposite sign
    separated by a distance d.


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39
Electric Dipole
  • Electric dipole consists of a pair of point
    charges with equal size but opposite sign
    separated by a distance d.


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40
Electric Dipole
  • Water molecules are electric dipoles



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41
Exercise 1
  • A point charge q -8.0 nC is located at the
    origin. Find the electric field vector at the
    point x 1.2 m, y -1.6 m

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Exercise 2
  • An electric dipole consists of a positive charge
    q and negative charge q separated by a distance
    2a, as shown in the figure below. Find the
    electric field due to these charges along the
    axis at the point P, which is the distance y from
    the origin. Assume that ygtgta.

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q
q
y
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Vector Flux
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Vector Flux
49
Vector Flux
  • Definition of flux

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Electric Flux
51
Electric Flux
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Gaubs Law
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Gaubs Law

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Gaubs Law

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Gaubs Law

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Gaubs Law

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Exercise 3
dE
R
L
s
r
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Solution
  • Coulombs Law

59
Solution
  • Infinitesimal area of disk

60
Solution
  • Infinitesimal area of disk

61
Solution
  • Y-component of E-field element

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Solution
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Solution
  • Y-component of E-field element

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Solution
  • Y-component of E-field element

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Solution
  • Y-component of E-field element

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Solution
  • Y-component of E-field element

67
Two Oppositely charged Parallel Plates (Capacitor)
s
-s
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Two Oppositely charged Parallel Plates (Capacitor)
s
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Exercise 4
r


















L
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Electric Potential
Charge with potential
Q
q
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Electric Potential
Source charge generates a potential at this
position
Q
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Electric Potential
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Electric Potential
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Electric Potential
75
Electric Potential
Electric potential at position P due to a system
of N source charges is given by
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Electric Potential
  • Potential difference

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Electric Potential
  • Potential difference

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Electric Potential
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Two Oppositely charged Parallel Plates (Capacitor)
s
-s
V
-V
80
Two Oppositely charged Parallel Plates (Capacitor)
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Capacitors and di-electrics
  • Capacitors store electric potential energy

Battery

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83
Capacitors and di-electrics

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Capacitors and di-electrics
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Capacitors and di-electrics
  • We can therefore express the voltage across the
    capacitor plates as follows
  • Hence

86
Exercise 3
  • A parallel-plate capacitor has an area of A
    2 cm2 and a plate separation of d 1mm.
  • Find its capacitance. (answer 1.77pF)
  • If the plate separation of this capacitor is
    increased to 3 mm, find the capacitance. (answer
    0.59 pF).

87
Capacitors and di-electrics
  • Capacitors in Parallel

88
Capacitors and di-electrics
  • Di-electric material inside a parallel Electric
    field.

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Capacitors and di-electrics
  • Di-electric material between parallel capacitor
    plates.

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Capacitors and di-electrics
  • Di-electric material between parallel capacitor
    plates.

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Capacitors and di-electrics
  • Di-electric material between parallel capacitor
    plates.

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Capacitors and di-electrics
  • Di-electric material between parallel capacitor
    plates.

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Capacitors and di-electrics
  • Di-electric material between parallel capacitor
    plates.
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