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. R

    Simple Electric field question -- Charged sphere

    Homework Statement A sphere with a charge of -3.5 x 10^-9 C and a radius of 1.0x10^-2 m is located at the origin of a coordinate system. What is the electric field 1.75 x 10^-2 m away from the center of the sphere along the positive y axis? Homework Equations e = kQ/r^2 The Attempt at a...
  2. D

    Electric Field of a cube with a rod

    Homework Statement The electric field at 2 cm from the center of long copper rod of radius 1 cm has a magnitude ##3 \frac{N}{C}## and directed outward from the axis of the rod. (a) How much charge per unit length exists on the copper rod? (b) What would be the electric flux through a cube of...
  3. T

    Electric field of a ring:integrate over dq or ds?

    Hi people, I was reading on my textbook on electromagnetism (Halliday) about using integral to field the electric field of a charged ring (1D) at a point P located on an axis perpendicular to the ring's plane. The ring is uniformly charged. The book (and my professor) both breakdown each element...
  4. RJLiberator

    EM: Electric field, Two thin rods uniform line charge

    Homework Statement Two identical thin rods of length L carry the same uniform line charge distribution (charge per unit length) of . If the two rods are collinear (aligned along the same line), with a distance of d between their nearest ends, calculate the Coulomb force (magnitude and...
  5. D

    Electric field of a positive plate

    Homework Statement There is a large positively charged plate whose charge density is ##\sigma = 2.0 × 10^{-5}\frac{C}{m^2}##. What is the electric field at a point P, that is not enclosed between the plates. Homework Equations For an infinite sheet: $$\vec E = \frac{\sigma}{2\varepsilon_0}\hat...
  6. K

    Deriving the energy density of the Electric Field

    Homework Statement Taken from Purcell Problem 1.33 Consider the electric field of two protons a distance b apart. The potential energy of the system ought to be given by U=∫E2dv. Let E1 be the field of one particle alone and E2 that of the other. Evaluate ε0∫E1⋅E2dv. Set one of the protons...
  7. D

    Particle traveling towards a plate with an Electric Field

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  8. N

    Finding the Charge on an Ion in a Zero Electric Field

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  9. D

    Electric Field between Two Thin Conducting Plates

    Homework Statement Two thin conducting plates, each 25.0 cm on a side, are situated parallel to one another and 5.0 mm apart. If ##10^{-11}## electrons are moved from one plate to the other, what is the electric field between the plates?Homework Equations $$\vec E(P) = \frac{1}{4\pi...
  10. W

    Calculating electric flux when given a charge (Gauss)

    Homework Statement A charge Q=5.14 nC is located at the center is located at the center of a Gaussian sphere of radius R=10.0 cm . The sphere lies within a uniform upward electric field E=2100 NC The net outward electric flux through the sphere is What? Second problem (bonus round!) A...
  11. Z

    Coulomb's force - magnitude of the electric force

    Homework Statement Show that the magnitude of the electric force on each ball is given by Fe = mgtanθ/ (cosα+ sinαtanθ) where θ = arcsin(x2/L) α = arcsin((y2-y1)/r) r = √((x2-x1)^2+(y2-y1)^2) This is a question from my coulomb's law lab, where 2 styrofoam balls where charged, one was hung on a...
  12. 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...
  13. B

    Electric field in an infinite layer

    Homework Statement In the layer ##0<z<a## there is a uniform and constant density of charge ##\rho>0##. In the layer ##-a<z<0## the density of charge is ##\rho<0##. What is the total electric field in the space?The Attempt at a Solution By the Gauss law I find that if ##z \geq a## or ##z \leq...
  14. R

    Finding electric potential of two concentric rings

    Homework Statement Two concentric spheres have radii a and b with b>a. The region between them is filled with charge of constant density p. The charge density is zero everywhere else. Hence, find the electric field of all points , then find the electric potential. 2. Homework Equations [/B]The...
  15. anorlunda

    The Perry Report on USA Electric Power

    Find the full text here Staff Report to the Secretary on Electricity Markets and Reliability I really like this report, it's right up my alley. It is professionally done. Every assertion of fact is documented with citations to reputable data sources. I found nothing outrageous in the 187...
  16. C

    Lateral electric fields in a lateral electrostatic actuator

    Hello, I'm reading through section 6.2.2 of https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-013-electromagnetics-and-applications-spring-2009/readings/MIT6_013S09_chap06.pdf on page 157. I understand all the math, but I have a conceptual questions that I don't seem to...
  17. B

    Electric field generated by ions in a box

    Homework Statement A ionized gas (overall neutral) is in a cylindrical box with radius ##R## and ##h<<R##, with is main axis along ##\hat{z}## (there is acceleration of gravity ##\vec{g}=-g \hat{z}##). The ions are points: some of mass ##M## and charge ##q>0## (heavy positive ions) and some of...
  18. J

    Angle between electric and magnetic field

    1. Homework Statement Hi. This is my first question on PF so please forgive me if something's not right So I'm stuck at this question in EMT In frame1, E and B are parallel and related by E=cB. We are required to find the cosine of the angle between electric field E' and magnetic field B' in...
  19. R

    What is Electric Field on a grounded structure?

    Suppose we have an energized conductor say 10m above the ground, my understanding is that E Field at the ground will be 0 v/m. My question is, if we have say 8m tall steel tower approximately 3m from the energized conductor and grounded. What is the electrical field on this grounded steel...
  20. T

    Electric motors vs internal combustion engines

    On average, which has higher power to weight ratio between the two? So on average, if both weighed the same, which one is going to have more power?
  21. T

    How exactly does an armature spin in an electric motor?

    In an electric motor, there exists two magnetic fields where usually one of them is a permanent magnet whilst the other is an electromagnet. However, how does the magnetic fields enable the armature to rotate / spin? Also, how is the torque from the rotation of the armature transmitted to drive...
  22. C

    Motion of Charged Particles in Electric Fields

    Homework Statement This is the question: An electron at rest of mass 9.11 × 10−31 kg is accelerated through a potential difference of 350 V. It then enters some deflecting plates of 50 V with dimensions as shown. Calculate the distance x (deflection of the electron) (Charge on an electron is...
  23. Harshna

    Engineering Find Currents I1 and I2 in an Electric Circuit

    Homework Statement I need to find the currents I1 and I2 in the attached image, but am having some difficulties grasping the concepts. I am given E(t) = 338sin(t) as well as values for R, L and C. I think I know what I need to use but I am not sure how to put it all together Homework Equations...
  24. R

    Electric Current and Potential Difference

    when the external electrical potential difference is applied across the conductor ,electrons flow in the direction opposite to the current.Whether the number of free electrons in the conductor decrease?
  25. rumborak

    Magnetic field = electric field in some reference frame?

    This Wikipedia article https://en.m.wikipedia.org/wiki/Relativistic_electromagnetism seems (to me) imply that there is always a frame of reference in which a magnetic field can be rather viewed as an electric field modified by relativistic considerations. Is that always true? That is...
  26. K

    How to determine efficiencies of electric heating systems?

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  27. Wrichik Basu

    Neutral wire in electric power distribution between substations

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  28. H

    Electric field generation between anode and cathode

    Hi I'm running an experiment where I want to see the electrical field generated when I energise a submerged anode (an array consisting of 4 x stainless steel tubes spaced equidistance apart) and cathode array (similar to the anode) upstream and downstream of the flowing water tank (glass sided...
  29. T

    Questions about friction losses in an electric motor

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  30. K

    Electric Field Lines: Charge Movement and Conductor/Insulator Interactions

    1. The problem statement "If charges are free to move, the field lines will straighten and shorten as the charges move together" 2. Questions in relation to statement Are there any cases in which charges aren't free to move between two charged objects such as between conductors or insulators...
  31. S

    What is the best software for the analysis of chaos in electric circuits?

    What is the best software for the analysis of chaos in electric circuits.
  32. Pushoam

    Electric Permittivity, Magnetic Permeability & Suceptibility

    Can anyone please explain me the physical significance of these concepts?? Electric permittivity, Magnetic Permeability & suceptibility
  33. Pushoam

    Electric field inside a cavity in a dielectric

    Homework EquationsThe Attempt at a Solution A)[/B] In the spherical cavity, let me have a Gaussian Spherical Surface around the center. Applying Gauss' s Law for dielectrics, ##\oint _S\vec D⋅ d \vec a = Q_{f_{en}} ## Due to the symmetry of the problem and ## Q_{f_{en}} =0## , ## \vec D = 0...
  34. T

    Can electric motors possibly apply continuous upward force?

    Is it possible for an electric motor to exist (based on our current understanding) which is capable of applying continuous upward force upon an object, enabling that object to fly or lift above the air?
  35. Pushoam

    Electric field due to a uniformly polarized cylinder

    Homework Statement Homework EquationsThe Attempt at a Solution Uniform polarization : ##σ_b = \vec P ⋅ \hat n ## Taking ## \vec P = P \hat x ~and ~ \hat n = \hat s ~, ~ σ_b = P \cos \phi ## Let's take a strip of width R dΦ at an angle Φ. This strip will be equivalent to a rod of linear...
  36. R

    Electric field of an infinitely long charge carrying wire

    Homework Statement Find the electric field of an infinitely long straight wire of charge ## \lambda## C/m at a point ##r= ix+jy## Homework Equations ##\int E.da = \frac {Q}{\epsilon_0}## ##E= \frac{\int dq}{4\pi\epsilon_0 r^2} ##r The Attempt at a Solution Drawing a cylindrical gaussian...
  37. Pushoam

    Sketching the electric field of a bar electret

    Homework Statement Homework Equations ##σ_b = \vec P ⋅\hat n The Attempt at a Solution The polarized system could be transformed into two charged discs S1 and S2 of radius a kept at a distance L. The discs S1 and S2 have surface charge densities -P and P respectively. A) For L>>a, In...
  38. A

    Electric field in leaky capacitor model

    Hi everyone. I need to calculate E-field(AC source / DC/ point charges) in leaky capacitor( epsilonr= a dielectric with relative permittivity and finite conductivity). But I do not how to calculate or write the equations for them. any idea or reference is very welcome.
  39. T

    What determines the maximum weight an electric motor can lift?

    What determines the maximum amount of weight an electric motor can lift / move for its size? So assuming the electric motor weighs a specific amount, what would be the limiting factor to how much weight it can move / lift for the weight it weighs?
  40. E

    Electric Field Intensity of a line on bisecting plane

    Homework Statement A very thin, finite, and uniformly charged line of length 10 m carries a charge of 10 µC/m. Calculate the electric field intensity in a plane bisecting the line at ρ = 5 m. Homework EquationsThe Attempt at a Solution Not sure why I'm not getiting this but I've been at this...
  41. Blank_Stare

    Electric conductivity loss due to weather on electric fence wire?

    Greetings Denizens!, I'm building a small "zapper" for the purpose of keeping critters away from a deer feeder. Other than volts and amps ratings, I believe it is, for all intents and purposes an electric fence, just in a unique configuration (shape, not electrical specs - those are within the...
  42. spareine

    Sketch of the electric field of a laser beam

    I am trying to sketch the electric field E in snapshot of a linearly polarized laser beam. Is it correct that the E vectors bend from vertical to longitudinal near the cylindrical surface of the beam, and that all field lines within a half wave segment are closed loops?
  43. C

    Electric field strength between charged plates help

    Homework Statement Homework EquationsThe Attempt at a Solution E=kq/d2 how do I involve the kinetic energy K in the equation?
  44. Domenico94

    Electric cars -- Does periodic coasting help efficiency?

    Hi. I'm a student of electrical engineering, and I've always been interested in the idea of electrical cars, so I came up with a question: let's suppose we want to have a normal trip with car, and then we're not interested in going so fast with it. When we are driving in this condition, it isn't...
  45. C

    Electric circuits -- Finding the V-I characteristics of a light bulb

    Homework Statement Homework EquationsThe Attempt at a Solution I know Ammeter and bulb goes in series and Voltmeters in parallel. But am I supposed to connect the voltmeter to the little arrow on the potential divider, or just across the bulb?
  46. davidge

    Can quantum mechanics be used to explain electric current in materials?

    Electric current can be studied using classical electromagnetism. In that case, the explanation is that there is a net flow of free electrons through a wire, say. Looking more close on the situation, what happens is that there is a difference on the energy level of some atoms and electrons can...
  47. C

    Electric field strength between charged plates

    Homework Statement Homework EquationsThe Attempt at a Solution E=kq/r2 so when the distance increase E should decrease? I know this is wrong, but can someone explain why? Thanks
  48. N

    Can electric energy be directly measured?

    I expect that power monitors directly measure the current, voltage change, and maybe phase to directly calculate current power use. Can electric energy directly be measured, or do meters just calculate power, and integrate it to obtain energy?
  49. A

    Understanding Electric Field Lines: An Introduction to E Bar and Tangent Vectors

    Hi, I'm reading the textbook and there is my image. http://imgur.com/a/9BqHm It says "The field vector E bar is tangent to the electric field line at each point". I might want to ask what "tangent" means in this sentence? Sorry to ask that stupid question.
  50. A

    Electric field of AC source

    Hello everybody I got really confused. I want to calculate the Electric-Field of an alternating current source( Sine(wt)). I do not know what is its equation. I need to run it in Matlab to get a result. Can you please give me some hints? I need to write the equation to calculate the E-field in...
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