Electrostatics Short notes | Electromagnetics - Electronics and Communication Engineering (ECE) PDF Download

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Electrostatics Notes
Introduction
Electrostatics is the br anch of electromagnetics that studies stationary electric
charges and their inter actions. It focuses on the forces, fields, and potentials as-
sociated with static electric charges, forming the foundation for understanding
electric circuits and electromagnetic phenomena.
K ey Concepts
• Electric Charge : Fundamental property of matter , measured in coulombs
(C), with positive an d negative types.
• Electric Field : Region around a charged object where forces are exerted
on other charges .
• Electric Potential : Energy per unit charge associated with a point in an
electric fiel d.
• Applications : Capacitors, electrostatic shielding, and analysis of charge
distributions i n electronics.
Fundamental Laws
• Coulomb’ s Law : The force between two point charges q
1
and q
2
separ ated
b y distancer :
F =
1
4p?
0
q
1
q
2
r
2
ˆ r
where ?
0
= 8.854 × 10
-12
F/m (permittivity of free space) and ˆ r is the unit
vector alon g the line joining the charges.
• Electric F ield Intensity (E) : F orce per unit charge on a test charge:
E =
F
q
=
1
4p?
0
q
r
2
ˆ r
• Gauss’ s Law : Relates electric flux through a closed surface to the enclosed
charge:
I
E·d A =
Q
enc
?
0
whereQ
enc
is the total charge enclosed b y the surface.
Electric Potential
• Potential E nergy (U ) : Energy due to the position of charges:
U =
1
4p?
0
q
1
q
2
r
1
Page 2


Electrostatics Notes
Introduction
Electrostatics is the br anch of electromagnetics that studies stationary electric
charges and their inter actions. It focuses on the forces, fields, and potentials as-
sociated with static electric charges, forming the foundation for understanding
electric circuits and electromagnetic phenomena.
K ey Concepts
• Electric Charge : Fundamental property of matter , measured in coulombs
(C), with positive an d negative types.
• Electric Field : Region around a charged object where forces are exerted
on other charges .
• Electric Potential : Energy per unit charge associated with a point in an
electric fiel d.
• Applications : Capacitors, electrostatic shielding, and analysis of charge
distributions i n electronics.
Fundamental Laws
• Coulomb’ s Law : The force between two point charges q
1
and q
2
separ ated
b y distancer :
F =
1
4p?
0
q
1
q
2
r
2
ˆ r
where ?
0
= 8.854 × 10
-12
F/m (permittivity of free space) and ˆ r is the unit
vector alon g the line joining the charges.
• Electric F ield Intensity (E) : F orce per unit charge on a test charge:
E =
F
q
=
1
4p?
0
q
r
2
ˆ r
• Gauss’ s Law : Relates electric flux through a closed surface to the enclosed
charge:
I
E·d A =
Q
enc
?
0
whereQ
enc
is the total charge enclosed b y the surface.
Electric Potential
• Potential E nergy (U ) : Energy due to the position of charges:
U =
1
4p?
0
q
1
q
2
r
1
• Electric P otential (V ) : Potential energy per unit charge:
V =
1
4p?
0
q
r
• Relation to Electric Field : E = -?V , where?V is the gr adient of the po-
tential.
K ey E quations
• Electric Field du e to Continuous Charge Distribution :
E =
1
4p?
0
Z
?( r
'
)
| r- r
'
|
2
ˆ rdV
'
where?( r
'
) is the charge density .
• Poisson’ s Equation : Relates potential to charge density:
?
2
V =-
?
?
0
• Laplace’ s Equation : Applies in charge-free regions:
?
2
V = 0
Capacitance
• Definition : Ability of a system to store charge, C =
Q
V
, measured in far ads
(F).
• Par allel Pla te Capacitor : F or plates with areaA and separ ationd :
C =
?
0
A
d
• Energy Sto red : Energy in a charged capacitor:
U =
1
2
CV
2
=
1
2
Q
2
C
Pr a ctical Consider ations
• Boundary Conditions : Electric field and potential continuity at interfaces
between dielectr ics.
• Dielectrics : Materials with permittivity ? = ?
r
?
0
, where ?
r
is the relative
permittivity , enhance c apacitance.
• Electrostatic Shielding : Conductors block external electric fields due to
zero internal fie ld in equilibrium.
• Numerical Methods : Finite element analysis or computational tools solve
complex charge di stributions.
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