Title: ELECTROSTATICS
1ELECTROSTATICS
2Outline
- Electric Force, Electric fields
- Electric Flux and Gaub law
- Electric potential
- Capacitors and dielectric (Electric storage)
3The physics of charged objects
- Study of electricity aims to understand the
interaction between different charged objects.
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4The physics of charged objects
- Study of electricity aims to understand the
interaction between different charged objects.
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5Structure 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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6Structure of Matter
- Neutral atom electron Positive ion
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7Structure of Matter
- Fundamental building blocks of the matter are
atoms.
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8Structure of Matter
- Neutral atom electron negative ion.
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9ELECTRICALLY CHARGING OBJECTS
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neutral object
10ELECTRICALLY CHARGING OBJECTS
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positive object
11ELECTRICALLY CHARGING OBJECTS
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negative object
12Charging by Induction
- In metals outer atomic electrons are not bound to
any atoms (electron see).
13Charging by Induction
- In metals outer atomic electrons are not bound to
any atoms (electron see).
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14Charging by Induction
15Electric Polarization
- Same atoms have weakly bound electrons.
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16Electric Polarization
- Same atoms have weakly bound electrons.
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17Electric Polarization
18The Electric Force
19Coulombs Law
- Quantifies the electric force between two charges.
20Coulombs Law
- Quantifies the electric force between two charges.
21Coulombs Law
- Quantifies the electric force between two charges.
22Electric Force Field
- Gravitational force field
23Electric Force Field
Q
24Electric Force Field
Q
q
25Electric Force Field
- Definition of Electric field
26Electric Force Field
- Definition of Electric field
27Electric Force Field
28Electric Force Field
- The electric field due to a number of source
charges is given by the expression
29Electric Force Field
30Electric Force Field(Linear distribution of
charge)
31Electric Force Field(Linear distribution of
charge)
32Electric Force Field(Linear distribution of
charge)
33Electric Force Field(Surface distribution of
charge)
da
34Electric Force Field(Surface distribution of
charge)
da
35Electric Force Field(Surface distribution of
charge)
da
36Electric 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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37Electric 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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38Electric 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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39Electric 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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40Electric Dipole
- Water molecules are electric dipoles
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41Exercise 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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45Exercise 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.
46q
q
y
47Vector Flux
48Vector Flux
49Vector Flux
50Electric Flux
51Electric Flux
52Gaubs Law
53Gaubs Law
54Gaubs Law
55Gaubs Law
56Gaubs Law
57Exercise 3
dE
R
L
s
r
58Solution
59Solution
- Infinitesimal area of disk
60Solution
- Infinitesimal area of disk
61Solution
- Y-component of E-field element
62Solution
63Solution
- Y-component of E-field element
64Solution
- Y-component of E-field element
65Solution
- Y-component of E-field element
66Solution
- Y-component of E-field element
67Two Oppositely charged Parallel Plates (Capacitor)
s
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68Two Oppositely charged Parallel Plates (Capacitor)
s
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69Exercise 4
r
L
70Electric Potential
Charge with potential
Q
q
71Electric Potential
Source charge generates a potential at this
position
Q
72Electric Potential
73Electric Potential
74Electric Potential
75Electric Potential
Electric potential at position P due to a system
of N source charges is given by
76Electric Potential
77Electric Potential
78Electric Potential
79Two Oppositely charged Parallel Plates (Capacitor)
s
-s
V
-V
80Two Oppositely charged Parallel Plates (Capacitor)
81Capacitors and di-electrics
- Capacitors store electric potential energy
Battery
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83Capacitors and di-electrics
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84Capacitors and di-electrics
85Capacitors and di-electrics
- We can therefore express the voltage across the
capacitor plates as follows
86Exercise 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). -
87Capacitors and di-electrics
88Capacitors and di-electrics
- Di-electric material inside a parallel Electric
field.
89Capacitors and di-electrics
- Di-electric material between parallel capacitor
plates.
90Capacitors and di-electrics
- Di-electric material between parallel capacitor
plates.
91Capacitors and di-electrics
- Di-electric material between parallel capacitor
plates.
92Capacitors and di-electrics
- Di-electric material between parallel capacitor
plates.
93Capacitors and di-electrics
- Di-electric material between parallel capacitor
plates.