What is Electric: Definition and 1000 Discussions

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. D

    I Charged black hole - static electric field lines

    Where do the static electric field lines appear to originate from a charged black hole, non rotating, Reissner–Nordström metric? I've had a number of qualified physicists say they appear to come from the center of the black hole, but people on these forums have said that doesn't make sense...
  2. A

    Electric Potential vs Electric Potential Energy

    So in my physics textbook a problem is stated. We are given an external electric field directed downwards of 150N/C. We are then told that an electron is released in the electric field and it moves upwards 520m. Finally we are asked to calculate the change in electric potential energy of the...
  3. Benjamin

    Calculating Electric Field from Force on a Point Charge

    Homework Statement What is the electric field at a point when the force on a 1.20 µC charge placed at that point is = (3.0 î -5.0 ĵ) × 10-3 N? Homework Equations E = KQ/d^2 The Attempt at a Solution I'm having trouble visualizing the question. I attempted to draw it out, but its not making...
  4. G

    What is the Simplified Equation for a Uniform Electric Field?

    Homework Statement [/IMG] Homework Equations See Below The Attempt at a Solution Maybe my answer is right but not simplified enough. But if it is I am having trouble seeing the mathematical equivalency. Please help. Thanks in advance!
  5. Matt Chu

    Angle of escaping electric field lines

    Homework Statement Two charges 2q and -q are located at x = 0 and x = a respectively. There are field lines extending from the positive charge and lines going inwards to the negative charge. Some of these lines go from the positive charge to the negative, but some go off to infinity from the...
  6. Brystephor

    Electric field magnitude between two charged disks problem

    Homework Statement Consider two thin disks, of negligible thickness, of radius R oriented perpendicular to the x axis such that the x axis runs through the center of each disk. (Figure 1) The disk centered at x=0 has positive charge density η, and the disk centered at x=a has negative charge...
  7. M

    How Do You Calculate Electric Field Strength and Direction?

    Homework Statement The diagram is attached. What is the strength of the electric field at the position indicated by the dot in Figure 1? What is the direction of the electric field at the position? Specify the direction as an angle measured clockwise from the positive x axis. Homework...
  8. T

    How exactly does the electric force act?

    greeting How exactly the electric force acts .The definition of force is In physics, a force is any interaction that, when unopposed, will change the motion of an object. as the electron circulates around the nucleus of the atom because of that I do not see how that force acts .
  9. G

    Help finding component of electric force

    Homework Statement [/IMG] In this problem I am trying to understand the solution for finding the net force on charge 3 due to charge 1. However, I am getting stuck already on F31x. Homework Equations F=kqq/r^2 The Attempt at a Solution I found theta by tan-1(0.5/1)=26.565degrees r= sqrt...
  10. L

    Calculate a charge distribution given an electric potential.

    Homework Statement Find the distribution of charge giving rise to an electric field whose potential is $$\Phi (x,y) = 2~tan^{-1}(\frac{1+x}{y}) + 2~tan^{-1}(\frac{1-x}{y})$$where x and y are Cartesian coordinates. Such a distribution is called a two-dimensional one since it does not depend on...
  11. M

    Electric field vector in component form

    Homework Statement A -12nC charge is located at (x,y) = (1.0cm, 0cm). What are the electric fields at the positions (x,y) = (5.0cm, 0cm), (-5.0cm, 0cm), and (0cm, 5.0cm)? Write each electric field vector in component form. Homework Equations E=k(q/r2) The Attempt at a Solution I was able to...
  12. L

    Finding the electric field between two parallel plates

    Homework Statement Hi everyone! This is the homework problem I'm struggling with! Initial velocity = 107 meters per second The particle is an electron, so: Charge = -1.6 x 10-19 coulombs Mass = 9.11 x 10-31 kilograms Homework Equations Kinematic formula x = vot + 1/2 at2 Newton's law...
  13. lawsonfurther

    Can there be an electric field inside an insulator?

    Just as the title asks, I wonder if there can be any electric field inside an insulator when a point change is placed near it. If so, why?
  14. A

    Confusion regarding Electric Potential Energy and Work

    Hi everyone. I've been doing a lot of reading regarding electric potential and electric potential energy. Unfortunately, I have a lot of confusion regarding this topic, as I keep receiving different information. My main confusion is regarding the signs, positive or negative, of work and it's...
  15. S

    Find the electric field at the point 20cm above the centre

    Homework Statement Hi guys, I was hoping I could get some help on this question! The question: "Find the electric field at the point 20 cm above the center of the square made of 4 charged rods of L = 20cm and Q=1mc each. Homework Equations I believe E = (KQ)/r^2 is the only equation needed...
  16. H

    How do you calculate Electric Potential Energy in a Square?

    Four identical particles, each having charge q and mass m, are accelerated from rest at the vertices of a square of side L. How fast is each particle moving when their distance from the center of the square doubles? I used the Conservation of Energy => Kf= -deltaU = Ui-Uf 4(mv^2 /2) = kq^2...
  17. B

    Calculate final velocity of electric particle

    Homework Statement A particle of mass 7.3 × 10−5 g and charge 24 mC moves in a region of space where the electric field is uniform and is 6.3 N/C in the x direction and zero in the y and z direction. If the initial velocity of the particle is given by vy = 4.1 × 105 m/s, vx = vz = 0, what is...
  18. starstruck_

    Calculating electric field strength

    Homework Statement A cylinder of radius R= cm 1.2 and length L= 51 cm has a charge Q=2.3 μC spread uniformly along its surface (and not on its flat ends). a) Calculate the electric field strength a distance d=4 mm from the cylinder’s surface (not near either end) b)Calculate the electric...
  19. R

    Electric field at the surface of a spherical shell?

    What is the value of electric field at the surface of a spherical shell?
  20. C

    Electric field between two cylinders in a vial

    Homework Statement Hello everyone, I am writing here regarding a doubt I have about electric fields. Our set up consists on two rod shape electrodes in a cylindrical glass vessel separated by 6 mm from each other, with one of the electrodes grounded (electrodes dimensions: 0.5 mm diameter and...
  21. F

    Which creates an electric field -- charge or a charged particle?

    wich creates an electric field charge or a charged particle (electron)
  22. F

    The difference between electric field and electrical charge

    what is difference between electric field and electrical charge?
  23. Hiero

    Does the superposition of electric fields not hold for moving charges?

    If a single point charge is moving, then the component of the electric field normal to the motion is larger (by the gamma factor) than if the charge were stationary. Now consider an infinite line of charges (with a small separation, the same between each charge). If the whole line is moving...
  24. lawsonfurther

    Electric Field Lines: Midpoint Between 2 Charges

    I notice from the classic electric field line diagram of two positive charges that there is no field line going along the line segment joining those two charges. So I wonder whether that is true or it's just a way that you can't show all the field lines in the diagram but it actually exists. (I...
  25. B

    Electric field in a capacitor with multiple dielectrics

    Hi, I am trying to understand capacitors and have come across the example in the attached image. What I would like to understand is how to calculate the electric field at some distance x within the capacitor. With x>>R , x<R and x=R . The image is of two circular disks as the...
  26. S

    Liquid crystals: dielectric torque and electric torque

    Dear Members, I was reading a tutorial on ferroelectricity of liquid crystals, underneath is the excrept: "For ferroelectric materials, in addition to the dielectric torque, the electric torque will have a term due to the linear coupling between the spontaneous polarization" Could someone...
  27. C

    Can an axisymmetric electric field be created without charges?

    That is, a field that accelerates charges in opposite directions on each side of an axis. I was thinking about interference of similarly polarized waves traveling in opposite directions (so that electric field peaks and valleys overlap but magnetic field adds constructively) - would there be an...
  28. H

    If r=0 then will the electric charge of two points=infinity?

    I found that the electric field at r=0 equals infinity. What if two negative charges were put infinitely close together so the electric field was infinite, then would the charge of those two points be -infinity as well?
  29. H

    Can We Develop a Material to Block Electric Fields Like Mu-Metal Blocks Magnetic Fields?

    Is it possible to create a material that will block an electric field like mu-metal blocks magnetic fields?
  30. Pushoam

    What is the relationship between induced emf and induced electric field?

    Homework Statement Homework EquationsThe Attempt at a SolutionThe emf gets induced due to the changing flux. The flux through the rod remains 0. So, there is no induced emf. I don’t know how to calculate induced electric field. But as there is no induced emf, so there is no induced...
  31. J

    Electric field intensity at a distance

    Homework Statement Homework EquationsThe Attempt at a Solution The radiations from the bulb spread radially outwards such that "Power at a distance r" = Power radiated/4πr2 . If distance is unchanged and power halved then the intensity should also be halved . From this I get E' = E/2 ...
  32. J

    Electric field varying with distance

    [Moderator note: moved from general physics, no template.] This is a solved example given in the book . Could someone help me understand how amplitude of electric field has an inverse relationship with distance ? Only the very basics of EM waves are covered in the book so I would appreciate...
  33. M

    Confusion about the electric potential

    Why the negative pole of a battery is said to be of higher potential? While if we a consider a DC battery of 12V (for instance) then we have Vpn=V (positive) -V (negative)=12V whish is a positive quantity, then we should conclude that Vp>Vn in contradiction to first statement! Please illustrate...
  34. SW Dad

    UV light + electric current = boom?

    Hi, so I was hoping to get an EE's explanation for what just happened. So my son was apparently over by the light switch pointing a UV pen light at the switch. Suddenly there was very loud, gunshot-like pop, sparks flew, and I had to go reset the breaker. Maybe correlation doesn't imply...
  35. sergiokapone

    Electric field lines of a sphere in a uniform electric field

    I need to draw electric field lines of sphere in uniform electric field with LaTeX/TikZ. Can anyone show me equation of field lines in polar coordinates?
  36. M

    Electric field of two conducting concentric spheres

    Homework Statement Two conducting hollow spheres are are placed concentrically, the inner sphere have a radius ra = 5 cm and the outer sphere have a radius rb = 15 cm. The charge on the inner sphere is qa = 4 · 10−7 C and qb = −4 · 10−7 on the outer sphere. (a) Use Gauss’s law to find the...
  37. T

    Electric Field between two flat metal plates

    Homework Statement Two large, flat metal plates are held parallel to each other and separated by a distance d.· They are connected together at their edge by a metal strip. A thirt plastic sheet carrying a surface charge \sigma per unit area is placed between the plates at a distance 1/3*d from...
  38. T

    Find the x component of the Electric Field

    Homework Statement Find the general formula for the x component of the electric field if the charge density p varies only with x throughout all space. Homework EquationsThe Attempt at a Solution I started using the poisson equation \bigtriangledown \bullet \bar{E} = \frac{p}{\varepsilon_{0}}...
  39. R

    Particle motion + electric field when voltage varies

    Homework Statement Two parallel plates located at a distance "L" from each other they maintain a potential difference "V" because of a battery (as shown in the picture). Through a small hole, made in bottom plate, electrons get into system (with mass "m" and charge "-e"), with velocity "v" and...
  40. T

    Which harmonics would be observed on an electric guitar?

    Homework Statement The electric guitar radiates very little sound directly, but instead relies upon pick-ups (transducers) placed beneath the strings. Establish, showing clearly how you reach your answer, which harmonics of the open string you are likely to observe if the pick-ups are placed...
  41. VSayantan

    Current through an Ammeter in an Electric Circuit

    Homework Statement [/B] It is required to find the current through the ammeter, marked A, in the above figure.Homework Equations ##V=iR##The Attempt at a Solution I've redrawn the circuit as follows - But don't know how to obtain the value ##i_3##
  42. aatari

    Electric Fields - Electron Passing through deflecting Plates

    Hi Guys, I have attempted the question below. Please have a look at my work and let me know if everything looks fine. Any feedback would be great. 1. Homework Statement Homework Equations F = qv/d a = F/m t = d/v qv = 1/2mv^2 x = vt + 1/2 at^2 The Attempt at a Solution
  43. F

    Electric field of a current carrying conductor along its sur

    Homework Statement I am trying to figur out whether there is or isn t an Electric Field along the surface of a cylindrical current carrying wire With radius r and length L, current I and resistance R. I was trying to see if someone already asked this and i found one discussion, however where a...
  44. L

    Electric dipole EM field using Lorentz Transformation

    Homework Statement An electric dipole instantaneously at rest at the origin in the frame K' has potentials \Phi'=\mathbf{p}\cdot\mathbf{r}'/r'^3 and \mathbf{A}'=0 (and thus only an electric field). The frame K' moves with uniform velocity \mathbf{v}=\vec{\beta }c in the frame K. Show that in...
  45. E

    Why is the electric field in an ideal wire zero?

    I’ve looked at the answers given to the previous times this question has been asked, but I still don’t seem to understand how this holds in the case of a closed circuit. Here’s an explanation given before: “Think of the wire as a horizontal cylinder. If you apply an electric field pointing to...
  46. N

    Linear polarizers: angle between the electric & magnetic fields

    From wikipedia: "An electromagnetic wave such as light consists of a coupled oscillating electric field and magnetic field which are always perpendicular; by convention, the "polarization" of electromagnetic waves refers to the direction of the electric field." A polarizer is an object that...
  47. A

    Negative work and electric potential energy

    I am confused how a charge could have negative work done. To clarify, I was doing a problem earlier in which a positive charge and negative charge are moving towards each other. I used the equation work = Δv * q And when I was doing this, the change in electric potential, Δv, was negative, and...
  48. G

    What about the electric field in a circuit with resistors?

    Hi. I am having some trouble understanding what is the voltage drop in a system with resistors in series. If there is a difference of electric potential between two points in space, since electric potential is electric potential energy per charge, there is a difference in the electric...
  49. S

    Electronics DIY Electric Lighter: Building with Alligator Clips and Pencil Resistors

    I have been building a electric lighter without soldering since I don't know how to solder, so I am going to ask my brother to show me how on the weekend. Until then I've been using alligator clips, 9 volt batteries (preferably one) and graphite from pencils as a resistor. Unfortunately the...
  50. L

    I Electric currents and length contraction

    Hi people, me bother yo again! I understand that relativity theory length contraction is the explanation of magnetics fields. See the image: https://dl.dropboxusercontent.com/s/vuy69jhig3kni3n/densidadcargasencorriente.jpg?dl=0 1) In the S system, if q is moving at the same velocity than the...
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