What is Gauss' law: Definition and 339 Discussions

In physics and electromagnetism , Gauss's law, also known as Gauss's flux theorem, (or sometimes simply called Gauss's theorem) is a law relating to the distribution of electric charge to the resulting electric field. In its integral form, it states that the flux of the electric field out of an arbitrary closed surface is proportional to the electric charge enclosed by the surface, irrespective of how that charge is distributed. Even though the law alone is insufficient to determine the electric field across a surface enclosing any charge distribution, this may be possible in cases where symmetry mandates uniformity of the field. Where no such symmetry exists, Gauss's law can be used in its differential form, which states that the divergence of the electric field is proportional to the local density of charge.
The law was first formulated by Joseph-Louis Lagrange in 1773, followed by Carl Friedrich Gauss in 1813, both in the context of the attraction of ellipsoids. It is one of Maxwell's four equations, which forms the basis of classical electrodynamics. Gauss's law can be used to derive Coulomb's law, and vice versa.

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  1. H

    I Gauss' law applied on a four-dimensional surface

    in a 4D plane or on a four-dimensional surface can gauss law be used?
  2. A

    Gauss' law: find the electric field

    Homework Statement A long, thin, straight wire of length 1.3 m has a positive charge 4.1 × 10-8 C distributed uniformly along it. The electric field created by this wire at a radial distance 3.2 cm has a magnitude of ε= 8.85E-12 Homework Equations I think I need to use E= q/(4πr^2ε) but I...
  3. Wrichik Basu

    Finding electric flux using Gauss' Law

    Say you have a hollow cylinder, whose one side is open. Now, you pace a positive charge ##Q## at the centre of this open end (such that it is just inside the cylinder). How much should be the flux coming out from the closed end? I just thought of this problem. In order to use Gauss' Law, we...
  4. Conductivity

    Permittivity in Gauss' law and Ampere's law

    In the derivation of the electric field inside a non conducting sphere, We still use the permittivity of free space even though we are in a medium. The same applies for ampere's law in a solid wire. http://physics.bu.edu/~duffy/semester2/c15_inside.html...
  5. SothSogi

    I Is my attempt to derive Gauss' law correct?

    Hi there. I am trying to derive Gauss's law from the divergence. I would like to know if it is correct: The divergence is defined as (I saw this on Fuller & Byron "Mathematics of classical and quantum physics") ##...
  6. S

    Apparent disagreement between Coulomb's Law and Gauss' Law

    This is probably my misunderstanding, so please clarify. In a region of empty space, there are two point charges with the charges+Q and -Q. Exactly in the middle of the two charges (distance r from both charges) is point P, colinear with the centers of both charges. A Gaussian surface that...
  7. Conductivity

    Is Gauss' Law for Magnetism Proven by Magnetic Field Lines?

    We took today in a lecture gauss' law for magnetism which states that the net magnetic flux though a closed shape is always zero (Monopoles don't exist). The professor explained/proved it as following (Since it needs math theorems): Draw any shape. From the fact that any magnetic field line that...
  8. Ignitia

    How Does Gauss' Law Apply to a Spherical Conducting Shell with a Central Charge?

    Homework Statement A point charge q=−5.0×10−12 C is placed at the center of a spherical conducting shell of inner radius 3.5cm and outer radius 4.0 cm. The electric field just above the surface of the conductor is directed radially outward and has magnitude 8.0 N/C. (a) What is the charge...
  9. F

    How Does Gauss' Law Apply to an Insulated Cylindrical Shell and Rod System?

    Homework Statement Question ==== An infinitely long insulating cylindrical rod with a positive charge ##\lambda## per unit length and of radius ##R_1## is surrounded by a thin conducting cylindrical shell (which is also infinitely long) with a charge per unit length of ##-2\lambda## and radius...
  10. lawsonfurther

    Applying Gauss' Law for Calculating Work Req'd to Move Charge

    Homework Statement A capacitor has two square plates that are d apart. Each plate is L×L. The capacitor is initially uncharged. (a)Calculate the work required to move q of charge from one plate to the other. (b)Calculate the work required to move an additional q of charge from one plate to the...
  11. Likith D

    Gauss' law for uniformly charged space

    the problem: Say we have the entire space uniformly charged. Then, the E field experienced by any point is zero, from symmetry.* But, it means that for any Gaussian surface, the flux though it is zero even though the charge enclosed is clearly not. Gauss' law seems to disagree with symmetry, but...
  12. Lucas Silva

    Gauss' Law: Charge of a Hydrogen Atom

    Suppose the hydrogen atom consists of a positive point charge (+e), located in the center of the atom, which is surrounded by a negative charge (-e), distributed in the space around it. The space distribution of the negative charge changes according to the law p=Ce^(−2r/R), where C is a...
  13. Const@ntine

    Gauss' Law: Charged Rod & Sphere (Electric Flux)

    Homework Statement A charged, straight line/rod of infinite length has a Discrete uniform distribution of charge, has a linear density of λ and is at a distance d from a sphere with a radius of R. Find the entirety of the Electrical Flux that is caused by this charged rod, which passes...
  14. Const@ntine

    Gauss' Law: Sphere with an Opening

    Homework Statement An uncharged, unconductive, hollow sphere with a radius R of 10.0 cm, surrounds an electric charge of 10.0 μC, which is found at the beginning of the axises, in a standard cartesian system. Parallel to the z axis, a small drill with a radius r = 1.00 mm opens a hole in the...
  15. Tom MS

    Why Does Diatomic Hydrogen Form Despite Zero Net Electric Field?

    Say you had two isolated hydrogen atoms. Because of the spherical distribution of electronic charge on each hydrogen and the net charge of 0 outside each atom, wouldn't Gauss's law dictate a 0 net electric field outside each atom? If this is the case, why does diatomic hydrogen so readily form...
  16. E

    Gauss' Law for electromagnetic radiation?

    For the proof I've read that verifies transverse electromagnetic waves are consistent with Gauss' Law, there seems to be the suggestion that the magnetic and electric field at a given small length c(dt), along which the waves travel, propagate infinitely backwards and forwards in their...
  17. T

    Understanding Gauss' law: diff b/w E and D flux?

    I noticed the other day something odd in how we use Electric and Magnetic flux. The definitions I refer to are magnetic flux density (B), magnetic flux intensity (H), electric displacement field (D) or Electric field density (D) and electric field (E): B = μH ΦB = B*Area & D = εE ΦE = E*Area...
  18. N

    Using Gauss' Law to Calculate electric field near rod.

    Homework Statement No variables, just a conceptual question. Homework Equations Flux = EA = Q/ε The Attempt at a Solution Given a uniformly charged rod of FINITE length, could we use Gauss' law for electric flux to calculate the field at a point p a distance x away from the rod, so long as the...
  19. NFuller

    I Understanding Gauss's Law: Where Does the Argument Break Down?

    So, this has been bothering me for a few days and I'm having trouble understanding where the fault is. If we consider a uniform charge density ##\rho## extending through all space, then by symmetry, I would argue that ##\mathbf{E}=0## in all space. However, this does not agree with what a naive...
  20. E

    Electric field outside conductor surface

    I'm confused as to how this expression E= (δ/εo) can't be used to calculate the electric field of a perfectly flat part of a surface even farther from just above the surface.If you just extend the same cylindrical Gaussian surface used for this proof, wouldn't the field stay the same no matter...
  21. GAURAV DADWAL

    B Solving Gauss' Law Problem for Varying Electric Fields

    I WAS THINKING ABOUT A REGION OF SPACE WITH ELECTRIC FIELD ALONG POSITIVE X DIRECTION AND Varying WITH SPACE COORDINATE(x) NOW IF ONE IMAGINES A CUBE IN SPACE SUCH THAT FIELD CROSSES ITS TWO FACES AT RIGHT ANGLES ,A SIMPLE Application of...
  22. AdrianMachin

    Confusion over electric field inside a charged shell

    I've got confused over a topic in my physics textbook (Fundamentals of Physics). The textbook says if a charged particle is enclosed by a shell of uniform charge, there is no electrostatic force on the particle from the shell. I don't firmly get this, as the book uses a confusing reasoning for...
  23. G

    Gauss' Law - Electric Field for a Charged Metal Plate

    Homework Statement An infinite metal plate has a surface density of charge σL=-6μC/m² , Left side and a surface density Of load σR=+4μC/m² , in the right side. A Gaussian surface In the form of a circular cylinder, with area A 12 cm², is Located with the left side inside the plaque and a thin...
  24. S

    I Why Do We Consider External Electric Fields in Gauss' Law Calculations?

    According to Gauss Law, we only consider charges which are inside the surface to produce net flux. We disregard the charges outside the surface because they produce zero net flux (as the electric field lines enter the surface and leave the surface producing zero net flux) My question is, since...
  25. Arman777

    Gauss' Law: Charge distribution on concentric spherical surfaces

    Homework Statement A metallic sphere of radius a is placed concentrically with a metallic spherical shell with inner radius b and outer radius c. The sphere has a total charge of 2Q and the shell has a total charge of 3Q. (a) What is the charge distribution? Specifically, what is...
  26. grandpa2390

    Gauss' Law -- Clarification about using the equation please

    Homework Statement I keep getting confused about this part of Gauss' law. Is the da on the left side the surface area of the the Gaussian surface? and on the right side when I am integrating. I say that q = the charge density multiplied by something. Is that something surface area of the...
  27. J

    Charge on a cavity wall and Gauss' law

    Homework Statement An isolated conductor has a net charge of +14.0 × 10- 6 C and a cavity with a particle of charge q = +4.30 × 10-6 C. What is the charge (a) on the cavity wall and (b) on the outer surface? Homework EquationsThe Attempt at a Solution So I understand that B is just adding the...
  28. A

    B How to find the appropriate area in Gauss' law

    Knowing that Gauss' law states that the closed integral of e * dA = q(enclosed)/e naut, how would you find exactly what A is in any given problem? I know it varies from situation to situation depending on the geometry of the charge. For instance, I know that for an infinite wire/line of...
  29. J

    Electric field inside a sphere

    I'm confused with the electric field inside a sphere. The book said that E=keQr/a^3 While one of the properities of electrostatic equilibrium mentioned that the E-field is zero everywhere inside the conductor. Are there any exceptional cases? Thanks in advance.
  30. pesslovany

    Application of Gauss' law - point charge in hollow sphere

    Firstly I appologize, that I am not native english speaker and I don't study physics(but cybernetics we are getting just some general knowledge about physics), but hopeffuly I will write this right. Homework Statement We know that inside of a conductive object is protected from influence of...
  31. G

    Faraday cage from Gauss' law alone?

    Hi. Is it possible to derive the properties of a Faraday cage from Gauss' law alone? I found some "derivations" which I find rather unconvincing since they somehow conclude from a vanishing flux that the E field must vanish as well. Some slightly more elaborate derivations use a combination of...
  32. G

    I Differential form of Gauss' law: All three terms the same value?

    Hi. Is the Maxwell equation $$\nabla\cdot\vec{E}=\frac{\rho}{\varepsilon_0}$$ even true in the stronger form $$\frac{\partial E_i}{\partial x_i}=\frac{\rho}{3\cdot\varepsilon_0}\enspace ?$$ I guess not, since I haven't found a source suggesting this. But shouldn't the isotropic electric field...
  33. D

    I Solving Gauss' Law Problem: Zero E Field?

    Lets consider a hollow sphere with charge +q and than a larger hollow sphere that encloses it with -q, so two spheres one inside the other. Now we use draw an even larger Gaussian sphere that encloses both of these, ∫EdA = Qinclosed/ ∈_0 the total enclosed charge is +q + -q = 0 so ∫EdA = 0 E...
  34. stephen8686

    B How does Gauss's Law relate to E=(2kλ)/r for an infinite line of charge?

    I was looking for a derivation of E=(2kλ)/r for an infinite line of charge. I understood that you need to use Gauss's Law and a cylinder around the line. When looked it up, I found this: http://www.vizitsolutions.com/portfolio/gausslaw/lineCharge.html He starts out with ∫E⋅dA=4πq. I have never...
  35. Blockade

    Need help in Electric Flux within a cube with Gauss' Law

    Homework Statement I need help in figuring out if I have done this problem correctly. From what I understand ∫E * dA = E*A, where E is the electric field and A is the area of a side. My biggest concern is if I can plug in the length "L" for the "x" and "z" variables within "E = -5x * E0/L i +...
  36. twist.1995

    Electric field discontinuity in a spherical shell?

    Homework Statement Lets say, there is a non-uniform charge distribution, given as in a spherical shell that has a cavity with radius a and the radius b to the outer surface. I am wondering if the field is discontinuous just on the surface of this sphere. Homework Equations...
  37. G

    Uniform E field for spherical shell.

    Homework Statement In the figure a nonconducting spherical shell of inner radius a = 2.07 cm and outer radius b = 2.51 cm has (within its thickness) a positive volume charge density ρ = A/r, where A is a constant and r is the distance from the center of the shell. In addition, a small ball of...
  38. A

    Calculating Electric Flux Through a Rectangle with Given Electric Field

    Homework Statement Hello, A 3.60cm x 4.50cm rectangle lies in the xy-plane. What is the electric flux through the rectangle if E=(80.0i + 50k) N/C ?Homework Equations Φ = E * A =EAcos(θ) The Attempt at a Solution My attempt: First convert the rectangle units from cm to m. 4.50cm = 0.045m...
  39. A

    How Do You Calculate Electric Flux Through a Rectangle?

    Hello, The problem: A 3.60cm x 4.50cm rectangle lies in the xy-plane. What is the electric flux through the rectangle if E=(80.0i + 50k) N/C ? My attempt: First convert the rectangle units from cm to m. 4.50cm = 0.045m 3.60cm = 0.036m Find the area of the rectangle. A = 0.036m x 0.045m =...
  40. K

    Spherical Shell using Gauss' Law

    Homework Statement An insulator is in the shape of a spherical shell. The insulator is defined by an inner radius a = 4 cm and an outer radius b = 6 cm and carries a total charge of Q = + 9 C (1 C = 10-6 C). You may assume that the charge is distributed uniformly throughout the volume of the...
  41. P

    I Why does Gauss' law hold for any closed surface?

    Why does Gauss' law hold for any closed surface? and can you show this mathematically. Many thanks :)
  42. RoboNerd

    Question about problem solving approach to Gauss' Law

    Homework Statement Hi, I am studying gauss's law via this book below.[/B] http://faculty.polytechnic.org/cfletcher/Phys%20With%20Calc_Vol_2_web_pdfs_2010/i-Ch14-PCALC--GAUSS'S%20LAW.pdf On page 8, and 9, the book describes the shell method of finding the volume of the sphere and then using...
  43. F

    Gauss' Law between infinite plates

    Homework Statement The volume between two infinite plates located at x=L and x=-L respectively is filled with a uniform charge density ##\rho##. Calculate the electric field in the regions above, between and below the plates. Calculate the potential difference between the points x=-L and x=L...
  44. J

    Gauss' Law for a coaxial cable

    Homework Statement I have attached the problem Homework Equations E*A = Qenc/ E0 The Attempt at a Solution At the moment I am looking at the problem more conceptually and seeing what is happening at each point and I wanted to know If I was on the right track. r<a As all charge would...
  45. P

    What is the charge on the outer surface of the middle conductor?

    Homework Statement Three concentric hollow spherical conductors are charged as follows: the inner conductor carries charge Q, the middle conductor carries charge -2Q, and the outer conductor carries charge -Q. What is the charge on the outer surface of the middle conductor? Homework Equations...
  46. ing_it

    Intensity of an electric field near a wire -- With and without Gauss' Law

    Homework Statement We have a wire of the length L=0.2m which is uniformly charged with a linear density of Lambda = 3nC/cm. Find the intensity (E) of the electric field in point A1 whose perpendicular distance from the wire is a=0.05m. The wire is in a vacuum. Compare the intensity with the...
  47. Idyia

    B Why doesn't the flux through a Gaussian surface change with a change in shape?

    Why doesn't the flux through a Gaussian surface change, when the shape is changed? (while keeping the net charge inside it the same) Flux is the dot product of electric field and surface area, so wouldn't it change if surface area is changed?
  48. S

    I Properties of body with spherical symmetry

    I'm studing Gauss law for gravitational field flux for a mass that has spherical symmetry. Maybe it is an obvious question but what are exactly the propreties of a spherical simmetric body? Firstly does this imply that the body in question must be a sphere? Secondly is it correct to...
  49. erick rocha

    Using Gauss's Law on two separated, and infinite plates

    Homework Statement The figure shows cross-sections through two large, parallel, nonconducting sheets with identical distributions of positive charge with surface charge density σ = 1.06 × 10-22 C/m2. What is the y component of the electric field at points (a) above the sheets, (b) between them...
  50. KT KIM

    Derive the Analog of Gauss' law

    I am stuck with this (d) all the other (a),(b),(c) were just like (a) E= −∇φ (b) ∇ · E= −∇2φ (c) ∇ × E I know only very basic about Gauss' law, the problem is not from Electrodynamics course. I don't know what should I do to solve (d)
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