Examples of electric fields

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Depending on the geometry of the distribution of charges, different electric fields are obtained.

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Gauss's law for a surface (1)

Equation

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With Gauss's law

$\displaystyle\int_S\vec{E}\cdot\hat{n}\,dS=\displaystyle\frac{Q}{\epsilon_0\epsilon}$



for the case that the field is normal and constant on only one surface we have

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$

ID:(11456, 0)



Gauss's law for two surface (2)

Equation

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With Gauss's law

$\displaystyle\int_S\vec{E}\cdot\hat{n}\,dS=\displaystyle\frac{Q}{\epsilon_0\epsilon}$



for the case that the field is normal and constant on two surface we have

$ E_1 S_1 + E_2 S_2 = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$

ID:(11458, 0)



Gauss's law for three surface (3)

Equation

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With Gauss's law

$\displaystyle\int_S\vec{E}\cdot\hat{n}\,dS=\displaystyle\frac{Q}{\epsilon_0\epsilon}$



for the case that the field is normal and constant on three surface we have

$ E_1 S_1 + E_2 S_2 + E_3 S_3 = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$

ID:(11457, 0)



Conductor sphere with charge

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In a conducting sphere with charges, these are distributed on the surface and with it the field inside is null. Outside it behaves like a point charge that is in the center of the sphere:

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Surface of a sphere

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La superficie de una esfera es con igual a

$ S = 4 \pi r ^2$

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A single point charge

Equation

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In the case of a spherical Gaussian surface, the field is constant, so it can be calculated by

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



with the surface of a sphere

$ S = 4 \pi r ^2$



At a distance r of a load Q is equal to:

$ E_p =\displaystyle\frac{1}{4 \pi \epsilon_0 \epsilon }\displaystyle\frac{Q}{ r ^2}$

ID:(11442, 0)



Sphere with charge

Equation

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Para el caso de una superficie gausseana esférica el campo es constante por lo que se puede calcular con charge $C$, constante de campo eléctrico $C^2/m^2N$, constante dieléctrica $-$, electric eield $V/m$ and surface $m^2$ mediante

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



con la superficie de una esfera con pi $rad$, radius of a circle $m$ and superficie $m^2$

$ S = 4 \pi r ^2$



A una distancia r de una esfera de carga Q de radio R es igual con pi $rad$, radius of a circle $m$ and superficie $m^2$ a:

$ E_f =\displaystyle\frac{1}{4 \pi \epsilon_0 \epsilon }\displaystyle\frac{Q}{ r ^2}\theta( r - R )$

ID:(11443, 0)



Loaded infinite wire or cylinder, in vacuum

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In a conductor wire or cylinder with charges, these are distributed throughout the object, behaving like a long chain of point loads aligned on the axis:

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Surface of a cylinder

Hypothesis

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The surface of a cylinder of radius r and height h is calculated according to:

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Linear load density

Equation

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La densidad lineal de carga se calcula como la carga dividida por la carga que contiene el conductor lineal con es:

$ \lambda = \displaystyle\frac{ Q }{ L }$

ID:(11459, 0)



Infinite wire

Equation

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In the case of a cylindrica Gaussian surface, the field is constant, so it can be calculated by

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



with the surface of a cylinder

$ S =2 \pi r h $



and the linear density

$ \lambda = \displaystyle\frac{ Q }{ L }$



At a distance r of a load per length \lambda is equal to:

$ E_w =\displaystyle\frac{1}{2 \pi \epsilon_0 \epsilon }\displaystyle\frac{ \lambda }{ r }$

ID:(11444, 0)



Infinite conducting cylinder

Equation

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Para el caso de una superficie gausseana cilíndrica el campo es constante por lo que se puede calcular con charge $C$, constante de campo eléctrico $C^2/m^2N$, constante dieléctrica $-$, electric eield $V/m$ and surface $m^2$ mediante

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



con la superficie de un cilindro con

$ S =2 \pi r h $



y la densidad lineal con charge $C$, conductor length $m$ and linear charge density $C/m$

$ \lambda = \displaystyle\frac{ Q }{ L }$



A una distancia r de un cilindro infinito de radio R con carga por largo \lambda es con charge $C$, conductor length $m$ and linear charge density $C/m$ igual a:

$ E_c =\displaystyle\frac{1}{2 \pi \epsilon_0 \epsilon }\displaystyle\frac{ \lambda }{ r }\theta( r - R )$

ID:(11445, 0)



Insulating sphere with homogeneous charge

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An insulating sphere in which charges have been homogeneously distributed, which cannot be moved because it is an insulating material, has an electric field that grows linearly inside and decreases with the inverse of the radius squared:

ID:(11450, 0)



Insulating sphere with full volume charge, exterior

Equation

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Para el caso de una superficie gausseana esférica el campo es constante por lo que se puede calcular con charge $C$, constante de campo eléctrico $C^2/m^2N$, constante dieléctrica $-$, electric eield $V/m$ and surface $m^2$ mediante

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



con la superficie de una esfera con pi $rad$, radius of a circle $m$ and superficie $m^2$

$ S = 4 \pi r ^2$



A una distancia r de una esfera aislante con carga Q en todo el volumen de radio R es con pi $rad$, radius of a circle $m$ and superficie $m^2$ igual a:

$ E_e=\displaystyle\frac{1}{4 \pi \epsilon_0 \epsilon }\displaystyle\frac{ Q }{ r ^2 }$

ID:(11446, 0)



Charge fraction

Equation

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In the case of a sphere of radius R with homogeneous charge, the Gauss surface for a smaller radius r contains a charge equal to

$ q =\displaystyle\frac{ r_i ^3 }{ R ^3 } Q $

ID:(11461, 0)



Insulating sphere with full volume charge, interior

Equation

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Para el caso de una superficie gausseana esférica el campo es constante por lo que se puede calcular con charge $C$, constante de campo eléctrico $C^2/m^2N$, constante dieléctrica $-$, electric eield $V/m$ and surface $m^2$ mediante

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



con la superficie de una esfera con pi $rad$, radius of a circle $m$ and superficie $m^2$

$ S = 4 \pi r ^2$



y la carga encerrada en la superficie gaussiana con charge $C$, encapsulated charge on Gauss surface $C$, internal radius $m$ and sphere radius $m$

$ q =\displaystyle\frac{ r_i ^3 }{ R ^3 } Q $



A una distancia r del centro de una esfera aislante con carga Q en todo el volumen de radio R es igual con charge $C$, encapsulated charge on Gauss surface $C$, internal radius $m$ and sphere radius $m$ a:

$ E_i =\displaystyle\frac{1}{4 \pi \epsilon_0 \epsilon }\displaystyle\frac{ Q r_i }{ R ^3 }$

ID:(11447, 0)



Infinite conductor plane with load

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In a conducting plane, a Gaussian surface can be defined as a cylinder. The side walls are orthogonal to the field, so the only part that contributes are the surfaces parallel to the plane:

ID:(11453, 0)



Surface charge density

Equation

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La densidad superficial de carga se calcula como la carga dividida por la superficie con es:

$ \sigma = \displaystyle\frac{ Q }{ S }$

ID:(11460, 0)



Infinite plate

Equation

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In the case of a flat Gaussian surface, the field is constant, so it can be calculated by

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



with the surface density of charges

$ \sigma = \displaystyle\frac{ Q }{ S }$



The field for an infinite plate with a charge density per area \sigma for the vacuum case (\epsilon = 1) is:

$ E_s =\displaystyle\frac{ \sigma }{ 2 \epsilon_0 \epsilon }$

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Two plates with opposite charges

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In the case of two plates with opposite charges there is a field of greater intensity between them. However, there is a minor field that can be described with field lines that emerge from one of the plates and return by giving an external turn to the opposite plate:

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Simple model for two plates with opposite charges

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To be able to calculate the field between the two plates in a simple way, it can be assumed that the external field is compensated and that most of it is only between the plates:

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Two infinity plate with opposite plates

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Para el caso de una superficie gausseana plana el campo es constante por lo que se puede con charge $C$, constante de campo eléctrico $C^2/m^2N$, constante dieléctrica $-$, electric eield $V/m$ and surface $m^2$ se calcular mediante

$ E S = \displaystyle\frac{ Q }{ \epsilon\epsilon_0 }$



con la densidad de superficie de cargas con charge $C$, charge density by area $C/m^2$ and surface of the conductor $m^2$

$ \sigma = \displaystyle\frac{ Q }{ S }$



El campo para de dos placa infinita con cargas opuestas con una densidad de carga por área \sigma para el caso del vacío (\epsilon = 1) es con charge $C$, charge density by area $C/m^2$ and surface of the conductor $m^2$:

$ E_d =\displaystyle\frac{ \sigma }{ \epsilon_0 \epsilon }$

ID:(11449, 0)



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