Electric Definition and 1000 Threads

Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others.
The presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges is an electric current and produces a magnetic field.
When a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. If the charge moves, the electric field would be doing work on the electric charge. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is typically measured in volts.
Electricity is at the heart of many modern technologies, being used for:

Electric power where electric current is used to energise equipment;
Electronics which deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies.Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. The theory of electromagnetism was developed in the 19th century, and by the end of that century electricity was being put to industrial and residential use by electrical engineers. The rapid expansion in electrical technology at this time transformed industry and society, becoming a driving force for the Second Industrial Revolution. Electricity's extraordinary versatility means it can be put to an almost limitless set of applications which include transport, heating, lighting, communications, and computation. Electrical power is now the backbone of modern industrial society.

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  1. S

    B Electric flux density and confusion about units

    My general understanding of electric flux density is 'electric flux per unit area'. This gives the SI unit N/C. But According the formula of electric flux density, D=eplison*E, the SI unit is C/m^2. How come the dimension in both cases not matching if both are true?
  2. S

    B Electric flux -- Which of these three definitions is correct?

    I have read three definitions of electric flux in textbook which is confusing me.. 1. Electric flux is the number of electric lines passing through any area of a surface. 2. Electric flux is the number of electric lines passing through unit area per second held perpendicularly. 3. Electric flux...
  3. J

    Are EMF Radiation Levels in Electric Cars Safe?

    What is power of EMF radiation inside of electric cars? What is frequency range, ELF?
  4. bluesteels

    Why Doesn't the E*A Equation Work for Electric Flux in This Case?

    Electric Flux = E*A = 5*6(0.05)^2. when i look up at other sources they use Electric flux = q/ (8.854*10^-12 [this is e]) equation but I am confused on why the E*A equation don't work. The answer is 0.02Nm^2/C
  5. V

    Electric field due to a charged infinite conducting plate

    As shown in figure below, the electric field E will be normal to the cylinder's cross sectional A even for distant points since the charge is distributed evenly all over the charged surface and also the surface is very large resulting in a symmetry. So the derived formula should also apply to...
  6. maayan_aloni

    I Exploring Oscillating Electric Fields for Dipolar Molecules

    Hi all! I was wondering, Is it possible, given a specific dipolar molecule, to create the perfect oscillating electric field so as to heat it and not, i.e. the water around it? What I'm basically asking is could there exist a specific microwave just for X and not all dipolar molecules without...
  7. LCSphysicist

    Electric force due to a moving charge

    I am having some problems involving the force that a source moving with speed v along the x-axis would exert on a test charge at the x axis. Moving to the frame of the source charge, we got that the electric field it exerts is $$E' = kq/x'²$$ Now, moving back to the lab frame, and considering...
  8. V

    B Why does charge oscillate in an electric dipole antenna?

    Picture: Energy source => LR Oscillator => Transformer => Transmission line => Electric dipole antenna => traveling wave Why would the charge even oscillate in the antenna as opposed to building up in the antenna? The transmission line + antenna is not a closed circuit right?
  9. VVS2000

    I Electric field due to polarized object

  10. Z

    Understanding the electric force felt by the charges on a sphere

    A thin shell in reality doesn't have zero thickness. Consider the image below, showing a cross-section of a small portion of the shell: Here we are considering a more general case in which we have electric fields of magnitude ##E_1## and ##E_2## on each side of the shell. Gauss's Law...
  11. F

    Engineering Find the electric field intensity due to a point, line, and plane

    Question: My attempt: Could someone please confirm my answer?
  12. F

    Engineering Calculating the charge if the electric field density = 0

    Question: Relevant Equations: My attempt: Could someone please confirm my solution?
  13. Z

    On which objects can we apply Gauss' Law to find the electric field?

    What am I missing? I also don't get the title of the section: "Charge distributions with enough symmetry for Gauss's Law". I thought Gauss's Law was valid for any closed surface enclosing a charge. I don't understand what "enough symmetry" means in the title above. I get that with symmetry...
  14. Z

    Electric field is constant around charged infinite plane. Why?

    Using Gauss's Law By using a symmetry argument, we expect the magnitude of the electric field to be constant on planes parallel to the non-conducting plane. We need to choose a Gaussian surface. A straightforward one is a cylinder, ie a "Gaussian pillbox". The charge enclosed is...
  15. Z

    Calculate the electric field due to a charged disk (how to do the integration?)

    I am interested in particular in the second integral, in the ##\hat{r}## direction. Here is my depiction of the problem: As far as I can tell, due to the symmetry of the problem, this integral should be zero. $$\int_0^R \frac{r^2}{(x^2+r^2)^{3/2}}dr\hat{r}$$ I don't believe I need to...
  16. Z

    Electric field created by two charged circular arcs?

    The strategy will be to figure out what ##dq##, ##\hat{r}_{dq,p}##, and ##r_{dq,p}## are, plug them into the expression for ##d\vec{E}_{p_r}##, then integrate over ##d\vec{E}_{p_r}## to obtain ##\vec{E}_{p_r}##, the electric field at ##P## due to the arc on the right. Then I will repeat the...
  17. M

    B Is a Battery-Electric Vehicle Really More Efficient Than a Gas Car?

    I read that a kg of gas provides about 13kWh (47.5MJ) of energy and that burning a kg of gas emits about 3.15 kg of CO2. So presumably a gas-powered engine emits 3.15/13 or about .242kg of CO2 per kWh of work, right? According to the EIA, the US electric grid emits about 0.85lb or 0.386kg of...
  18. F

    I Electric field of uniformly polarized cylinder

    Hi all, I have a doubt when calculating the electric field of a uniformly polarized cylinder P along its longest axis. The cylinder has length L and radius a. Using Gauss's law: $$\int D\cdot ds = \rho_{f} =0 \, \, (eq .1)$$ The electric field inside of cylinder would be: $$E =-...
  19. Hamiltonian

    The Net Electric Field Inside a Dielectric

    The net Electric field(inside the dielectric): $$E_{net} = \frac{1}{4\pi \varepsilon_0 \varepsilon_r} \frac{q}{r^2}$$ $$\vec E_{net} = \vec E_{applied} - \vec p$$ where p is the polarization vector. let charge ##q_{-}## be present on the inner surface of dielectric and ##q_{+}## on the outer...
  20. Dezzi

    Electric field problem -- Repulsive force between two charged spheres

    I attempt to solve the problem in the picture below.
  21. O

    How to wind a brushless motor (number of windings per stator)

    Hi folks, I'm searching for information/procedure and also calculations/equations on how to correctly wind a stator on a (general or DC 3-phase) brushless motor? I.e. how to wind a copper wire X number of times around the stators, and thus get the desired performance/force that is required...
  22. R

    Electrostatics help please -- Electric field, potential

    Hello, any answers appreciated: 'Two spheres are 5 m apart. Sphere 1 has a charge of -20 mC and sphere two has a charge of -50 mC. (a) Find the strength of the electric field at the sphere's halfway point. (b) Find the electric potential at the halfway point
  23. A

    Conductivity and Electric Field relationship

    Okay so this is how it looks like,and there are the given values; a) I've tried it like this. So I now this formula $$ E = \frac{J}{\sigma} $$ where sigma is the conductivity value. Now to get E we need this formula; $$ U = \int_{l}{} E \ ds ] $$ Now to get U we can use the ## U = \frac{P}{I}...
  24. LCSphysicist

    Intensity and electric field amplitude

    Hello. I am having some trouble to understand the resolution of this question. We could easily try to calculate the electric field relative resultant at the screen. The problem i am having is about the amplitude of the electric field: Generally, we have that the intensity part dependent of the...
  25. patric44

    A problem in graphing electric field lines

    hi guys our instructor asked us to try to graph the projection of the electric field intensity at a certain point p(x,y) , for two charges q+-q located at (-a,0) , (a,0), Now starting with the equation $$\frac{dy}{dx} = \frac{E_{y}}{E_{x}}$$ after transforming this equation I got...
  26. A

    I Drude model with and without an electric field

    Why in the Drude model without e-field no energy is transfer by electrons to ions, but when there is an e-field electrons transfer energy to ions ?
  27. Narayanan KR

    Orientation of Electric Fields in a Bucking Coil Setup

  28. A

    Finding the value of the electric charge

    Hello! I am susposed to find the force of q3.The problem is given as in the picture ; Now we are given a hint,and it says the following: "First calculate the forces of the individual charges on q3. The superposition principle says that you can then simply add these forces vectorially to get...
  29. mohammed

    Solving Electric Field Vector Problems Using Gauss's Law

    I'm preparing for exam but it seems I can't find problems similar to this on the internet. Here I will apply Gauss's law on the electric field vector to get the charge density. but the problem is that I can't find similar examples on the internet that uses direct vectors on Maxwell's equations...
  30. Ugnius

    Electrostatic potential and electric field of three charges

    So I started with b) and it there was no q2 this would seem reasonable I was wanted to ask , what effect does q2 have on potential of these two charges? Because it has to be given for a reason.
  31. Shreya

    Variation of Electric Field at the centre of Spherical Shell

    My approach is thus: the shell will have induced charges if it's conducting resulting in E at the centre of shell(though flux at centre will be 0). For non conducting spheres there can be no induction only polarization of dipoles, therefore the E field at centre will remain 0. Is my approach...
  32. M

    I Build Setup to Create Electric Damping Force

    Hello! Is it possible to build a setup (containing time dependent and independent electric fields), such that a charged particle will feel a force proportional to its velocity i.e. ##ma = -\alpha v##?
  33. guyvsdcsniper

    I Electric Potential -- Is my understanding correct?

    I have been having a hard time understanding Electric Potential and believe I finally have a grasp on what is trying to say. I wanted to right out my understanding here and hopefully have someone confirm what I am saying is somewhat accurate as I feel like when you write stuff out you tend to...
  34. F

    Engineering Wireless Electric Vehicle Charging

  35. guyvsdcsniper

    Why Does the Potential Energy Calculation for a Dipole Yield a Negative Value?

    So the change in potential energy is ∆U = Uf-Ui. Final minus initial. If i solve the above problem like this I end up with a negative value. The way the person in the attached work solved the problem, is they used ∆U = Ui-Uf. How are the switching Ui and Uf? What is it I am missing?
  36. guyvsdcsniper

    Help finding the Electric field at the center of charged arc

    I am having trouble understand where area circled in red. I get that lamda is Q/L. The charge is +Q. Length is pi/R/2. I am having trouble understanding why the length is pi/R/2? Is it because the circumference of a circle is 2*pi*R and since we have broken this problem down to just...
  37. Ugnius

    Thin Charged Isolated Rod -- Find the electric field at this point

    Hi , I've been trying to manage a solution in my head and i think I'm on the right path , i just need some approval and maybe some tips. So it's obvious I can't solve this without integration because law's only apply to point charges , and i can't shrink this object to a point as i could do with...
  38. Sagittarius A-Star

    COVID Electric field of moderate strength inactivates Covid-19 virus

    A science team from the university of Kassel (Germany) proved with a physical model, that a moderate electric field inactivates the Convid-19 virus. Source: https://www.nature.com/articles/s41467-021-25478-7 via...
  39. V

    Electric Flux for a cube problem

    I have tried to understand the solution given in the book which is as pasted below. The solution uses Gauss's Law but makes no mention of which Gaussian surface is used. The diagram that I have used to understand this problem is also given at the end. From the diagram, faces OADG, OABE and OEFG...
  40. Alex Schaller

    B Different formulas for electric flux

    I noticed that in some textbooks (Physics - Tipler) the electric flux formula is different than in other textbooks (Engineering Electromagnetics -W. Hayt) Which one should we use?
  41. V

    Dipole placed in a uniform electric field

    My understanding is that the uniform electric field ##\vec E## cannot be the net electric field since the dipole creates its own electric field as shown in first diagram below, which must superimpose with the uniform electric field. So, yes, the uniform electric field ##\vec E## around the...
  42. bob012345

    I Divergence of the Electric field of a charged circular ring

    In a previous thread* the field in a charged ring was discussed and it was shown to be not zero except at the center. In *post #45 a video is referenced that says the field diverges as one gets close to the ring and it was argued that at very close distances the field looks like an infinite line...
  43. S

    EMF due to Lorentz electric and magnetic forces

    Example of emf due to Lorentz magnetic force is motional emf. When rod PQ moves to the left, there will be downwards magnetic force acting on the positive charge in the rod PQ so point Q is at higher potential compared to point P so there will be potential difference (emf) between P and Q The...
  44. K

    Electric field in a rotating rod in a magnetic field

    The first part of the problem seems easy enough, the free electrons in the wire would move in a circle owing to an electric field that would be induced in the rod which would provide the centripetal force for the same (Please correct me if I am wrong). So we have $$eE=mω^2x$$, where e is the...
  45. P

    A Phase diagram of Carbon at large electric fields.

    I am wondering if the phase diagram of Carbon has been explored at very large electric fields. Can one make any theoretical guesses ? In specific I am interested in Pressure Vs Electric field and Electric field vs Temperature at fixed temperature and pressure respectively.
  46. bboo123

    I Exploring the Impact of Dielectrics on Electric Flux Density

    In the 7th edition of the book "Elements of Electromagnetics by Matthew N. O. Sadiku" On page 190 the author goes on to say: "We now consider the case in which the dielectric region contains free charge. If ##\rho_v## is the volume density of free charge, the total volume charge density...
  47. ZdMh

    Electric spark between person and another person/thing

    Hello All! You know sometimes you touch another person and you felt an electric spark between both of you, or sometimes with things like the door handle, etc. I moved lately to a hot and dry country where the temperature is around 40-45 Celcius degrees now in August, but since I moved here this...
  48. V

    Electric field at a point within a charged circular ring

    I have broken the ring into a top arc and a bottom arc. First, let's assume an imaginary charge of +1 C is placed at point P. We will determine the force on this unit charge from top and bottom arcs. The charges in the top arc will result in electric fields that will all cancel each other...
  49. F

    B Tangential part of the potential electric field

    Good afternoon to everybody. I have may be a stupid question according to the tangential part of the electric field near the surface of the conductor. Why is it zero? The normal part is zero on the distance of Debye cause of screening. But is this situation the same for horizontal direction...
  50. V

    Electric Field on the surface of charged conducting spherical shell

    When I look at the relevant equations, then there is no mention of field for a point on the surface of the shell, so it gets confusing. On the other hand, I feel the radial E will get stronger as we approach the surface of shell and magnitude of E will approach infinity.
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