Electric Definition and 87 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.

View More On Wikipedia.org
  1. T

    Misc. Looking for entry level DIY ideas

    I'm looking for a way to use these batteries that is safe and also useful. I've looked into buy inverters to turn them into portable battery packs but am out of my depth and don't want to create a device with serious potential fire hazards without thoroughly understanding the ins and outs and...
  2. M

    Charge density on the surface of a conductor

    I have tried to solve the problem by setting as a condition that the electric field inside the conductor has to be 0, but in this way I have two unknowns (σ1 and σ2):
  3. bluesteels

    Electric field / Gauss's Law --

    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
  4. 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...
  5. J

    Electric current calculation

    According to the circuit in the figure; Can you calculate the values of the currents I1, I2, and I3. Can you send me a detailed solution to understand?
  6. DerbisEternal

    Two Charged Balls on Strings

    Given the total angles in the x direction, I set up this: (mg/cos(x))*sin(x)-Fe=0 then isolated for x: mgtan(x)=(kq^2)/(2*sin^2x) sin^2(x)*tan(x)=(kq^2)/(2mg) From here I am stuck. How do I go forward when x is contained in two different trig functions on the left?
  7. G

    Electric field and electric potential exercise

    a) \vec{F}=\vec{E}\cdot q \phi =\oint \vec{E}d\vec{S}=\oint \vec{E}d\vec{S}=\underbrace{\oint \vec{E}d\vec{S}}_{\textrm{FACES } \perp}+\underbrace{\oint \vec{E}d\vec{S}}_{\textrm{FACES } \parallel}=0+\oint EdS\cdot \underbrace{\cos 0}_1= E2S \dfrac{Q_{enc}}{\varepsilon_0}=\phi \left...
  8. B

    Electric Fields: calculate the resultant force

    Summary:: I try to find the resultant force on "q". I think I have to find the value of Q, but I'm not sure. I Know F1 = k|q * 2Q| / 3² and F2 = k|q * Q| / 2² Hi, this is my first post on this forum I hope I posted in the right section. I try to find the resultant force on "q". I think I...
  9. G

    Gauss-Theorem on a solid dielectric sphere

    The load system formed by the point load and the load distribution generates two regions in space corresponding to r<1m and r>1m, i.e. inside and outside the sphere. Given the symmetry of the distribution, by means of the Gaussian theorem we can find the modulus of the field at a distance r from...
  10. Eucliwood

    Theoretical vs measured electrical resistance: Percent error relation

    Mentor Note -- Thread moved from the technical forums, so no Homework Template is shown. So, we've conducted an experiment on resistors in a circuit. The theoretical calculation was based of on E-24 series color band table and the measured resistance of the resistor was measured by a meter...
  11. Aryamaan Thakur

    Electric potential at the edge of a thin charged circular plate

    My question might sound stupid to you but please clear my confusions. I'm taking an circular arc like element on the plate. That arc has a radius of 'r' (AB) and the radius is inclined at an angle 'θ' with OA (∠OAB). The area between arc of radius r and r+dr is dA. dA = 2θr.dr The charge on...
  12. G

    Electric dipoles

    What is the convention? Because the field lines leave the positive charges and enter the negative ones, do not they?
  13. F

    Is Electric armour feasible with current technology?

    I read about electric armor (also known as dynamic armor or electric reactive armor) that can protect armored vehicles from shaped charges of anti-tank weapons and I want to know if its feasible today. according to wikipedia: [Moderator: please don't do this without a link. The link is The link...
  14. Cathr

    Finding Fresnel coefficients from the interface conditions

    Homework Statement We have an incident electric field, and there are two cases: 1) the field is polasised perpendicularly to the incidence plane (TE) 2) polarised in the plane (TM) Here I must be able to correctly apply the limit conditions, to find the Fresnel formulas that give the...
  15. José Ricardo

    About the efficiency of engines

    if we had an entire car made of Starlite (a material that was created resistant to 18032 °F). Would the efficiency of the combustion engine be close to that of the electric and that of the electric would be almost 100% efficient? https://en.wikipedia.org/wiki/Starlite
  16. J

    Power required to compress air in a gas turbine

    I'm looking for advice on how much power is required to compress air in a gas turbine engine - parameterised by degree of compression and mass flow. Normal gas turbine engines have exhaust turbine(s) on the same shaft as the air compressors. They bleed some of the exhaust energy to drive the...
  17. Captain Levi

    Someone help explain electric dipole situation

    Ok so she says that electric dipoles are of opposite charge but equal magnitude at 3:40. But then at 5:33 she shows 2Q with -Q, at that point the magnitude of the 2Q particle wouldn't be equal to the -Q so they wouldn't be electrical dipoles right?
  18. H

    Speed/acceleration calculations for an Electric motorcycle

    Good day all, This is my first post here, hope you all are able to help me out here. I am thinking about converting an old Suzuki GS500E from an internal combustion engine to an electric motor. At the moment I am having some difficulties with the physics side of things, I would like to...
  19. J

    Applying Kirchoff's loop rule

    Homework Statement Homework Equations Kirchoff's Rule The sum of all V = 0 The Attempt at a Solution [/B] I think I'm having a problem determining the current at r_2 and R_3. I had originally thought the currents at both resistors would be I_3, writing E_2 — r_2 I_3 — R_3 I_3 — I_1 R_1 = 0...
  20. A

    Could a spacecraft refuel from the atmosphere?

    https://phys.org/news/2018-03-world-first-air-breathing-electric-thruster.html If it dipped into the atmosphere temporarily on an elliptical orbit, could the air gathered be stored for a long flight? Then maybe get more fuel from another planet's atmosphere or moon for the return trip?
  21. sam charlton

    Supercapacitors for dummies?

    Hello, what is the consensus on using super capacitors to power a 500w electric bike motor. cheap and innovative alternative to li-po batteries or explosion between thighs waiting to happen? the plan is to create something like this: i will use a 24V motor...
  22. sam charlton

    Problem with a dimmer switch

    Hello, I'm currently constructing an electric bicycle using a 500w 24v motor, 2X24v 7ah batteries (maybe 4 later on). I bought a 24v 30a dimmer switch to use as a "throttle". During the intitial test (on a table, not on the bike!) It worked absolutely fine for 2 minutes, but then began to smoke...
  23. D

    Magnitude of the Electric Field at the Following Distances

    Homework Statement The figure below shows a spherical shell with uniform volume charge density ρ = 1.87 nC/m3, inner radius a = 15.0 cm, and outer radius b = 2.60a. [Reference Picture] What is the magnitude of the electric field at the following radial distances? Homework Equations...
  24. P

    Emitting one or two opposite charges along the x-axis

    Let's consider that I have an emitter that can emit both negative and positive electric charges. Here let's consider only scenarios with two particles (one negative and one positive) that start initially at the tip of some electrode, where one or both the charges will separate from at the same...
  25. G

    Electric field integral: Convergence where ρ is nonzero

    Hi. I know how to use Gauss' Law to find the electric field in- and outside a homogeneously charged sphere. But say I wanted to compute this directly via integration, how would I evaluate the integral...
  26. T

    Engineering Solving Circuit Diagram

    Homework Statement [/B] A screenshot with everything given Homework Equations No idea The Attempt at a Solution No idea I'm not sure how to solve this or where to look for a solution. I was given this yesterday and have a test tomorrow. The professor has not gone over this at anytime...
  27. jlmccart03

    Calculate electric potential from a graph

    Homework Statement A region of space has a non-uniform electric field that points in the +x-direction and has magnitude as shown in the figure (Figure 1) As a reference point, take the potential at the origin to be -140 V . Calculate the electric potential at x=3.0m. Express your answer to two...
  28. jlmccart03

    Finding the magnitude of electric field

    Homework Statement A uniform electric field exists in the region between two oppositely charged parallel plates 1.59 cmapart. A proton is released from rest at the surface of the positively charged plate and strikes the surface of the opposite plate in a time interval 1.50×10−6 s . Find the...
  29. ckcurtis

    500cc 50hp electric motor swap

    Hi, I own a 1993 ex500 with that is having engine problems, I would like to swap the motor for one that is has more or equal power. The best specs I can come up with are these the motor puts on the rear wheel, HP 50, Torque 31 ft-lbs, top speed 130mph, I am looking into getting a DC-liquid...
  30. G

    Does current flow back to the power plant through the ground?

    Hi. I fear I might not have understood some fundamental concepts about electric power transmission. So we have "neutral" which is brought to Earth potential. Does this mean the electrical circuit from the power plant over highly conductive aluminium cables to my home closes back to the power...
  31. Kelsi_Jade

    Design a series RLC filter for 10kHz

    Homework Statement Design a series RLC filter for 10kHz using an 0.01mF capacitor. Homework Equations / 3. The Attempt at a Solution how would the circuit actually look if drawn out here? [/B]
  32. W

    A question on E Flux and Fields

    Homework Statement 1. The field for an infinite charged sheet is found to be σ/2ε0. If we place 2 infinite sheets of opposite charge above one another, we say that the field in between the sheets is σ/ε0 due to the superposition of individual fields. Why can't we say the same for a situation...
  33. P

    Does the first maxwell equation apply only....

    For static electric fields? does it apply also for a generic electric field? Let's say, moving charges inside a closed surface? If there are charges accelerating in a closed surface a part of the electric field is due to the charges, and a a part is due to the fact that the charges acceleration...
  34. jlmccart03

    Find ratio of diameter of two Cylindrical Resistors?

    Homework Statement Two cylindrical resistors are made from the same material and have the same length. When connected across the same battery, one(A) dissipates twice as much power as the other(B). Find ratio of dA/dB. Homework Equations P = VI = V2/R = I2R Area of cylinder = 2πrh + 2πr2 The...
  35. jlmccart03

    Total energy within a specific region.

    Homework Statement A cubical region 1.0 m on a side is located between x=0 and x=1 m. The region contains an electric field whose magnitude varies with x but is independent of y and z: E=E0(x/x0), where E0 = 32 kV/m and x0 = 6.0 m . The answer needs to be in μ J. Find the total energy in this...
  36. Cocoleia

    Electric field above a charged square loop

    Homework Statement Homework Equations The Attempt at a Solution I have the complete solutions for this problem, I just don't understand them: This is the first part. I don't understand what r' is, or how we found it. Otherwise I understand the concept of the problem just not the details...
  37. theideasmith

    Difference in potential energy of two charge configurations

    Chapter 24, Question 61 Given two configurations, ##C_1##, ##C_2## of ##N## point charges each, determine the smallest value of ##N## s.t. ##V_1>V_2##. ##C_1##: ##N## point charges are uniformly distributed on a ring s.t. the distance between adjacent electrons is constant ##C_2##: ##N-1##...
  38. fuvest

    Electrical Circuit Problem / Electric Potential Difference

    Homework Statement In the following picture, the absolute value of the difference in electric potential, between points A and B is: A)5V B)4V C)3V D)1V E)0V Homework Equations E =qV V = iR The Attempt at a Solution I have no idea where to start on this one, just started my electric...
  39. jlmccart03

    Electric Flux confusion and help

    Homework Statement I have three questions spanning three different situations, but each deal with the single concept of electric flux. Problem 1: Write an expression for the net electric flux through the entire surface in terms of the area vectors and the electric field E. Problem 2...
  40. W

    Electric Fields and Flux

    Homework Statement Not so much of homework questions but more to do with clarifying concepts: 1. How do i assess whether or not field lines emitted by charged objects (i.e uniformly charged cube) are both perpendicular to their surfaces uniform? This is in relation to taking the E of ∮φ = EdA...
  41. Abwi

    Electric force between two spheres

    Homework Statement [/B] Find the electric force between the two spheres. Sphere r=b-a has a volumetric density of p=K, where K is a constant Sphere r=a has a volumetric density of p=θ*r Homework Equations As you can see the sphere of radius 'a' doesn't have a uniform electric field because...
  42. Denny Lai

    Combining 2 AC power suppy

    As per the diagram, how do i change the wiring of the equipment on the outside to achieve my desired setup?
  43. L

    Really confused about voltage and some other quetions

    Please explain how or why (I have zero knowledge in physics).. 1. is Voltage the energy required by the elctrostatic forces between 2 points to move a certain quantity of charge between them? 2. Why is it called potential difference? Does this have to do with the difference in potential energy...
  44. T

    Electrostatics/Electric Field Question

    Homework Statement What is the magnitude E of the electric field at point P? Throughout this part, express your answers in terms of the constant k, defined by k = 1/(4πE0) To solve this question, I am trying to walk through the hint process. Question 1: Find the magnitude dE of the electric...
  45. K

    Diesel Electric Locomotive formula

    What formulas do Diesel Electric Locomotive manufactures use when designing new Locomotives? Are there any good books on the subject? Locomotive meaning train engine. I want to understand freight engine designs not passenger. Thank you, Kevin
  46. T

    Curvature of electric field around center of a quadrupole

    Hello all. I am working on a research project involving the Stark effect and its application in molecular guides and came across a bit of math in a paper that I don't understand. In this paper http://arxiv.org/abs/physics/0310046 there is an equation in the introduction concerning the electric...
  47. M

    Difference between electric, electrical and electrostatic

    Homework Statement Is there a difference between electric, electrical and electrostatic force? Homework Equations The Attempt at a Solution I used them interchageably. Is it incorrect?
  48. S

    B Question about the math involved in E-field calculations

    When calculating the electric field from a point above a line of charge using coulomb's law, the integral that comes up is of the form \int { \frac { dx }{ { x }^{ 2 }+{ a }^{ 2 } } } . But if the point we were asked for is right in the middle, the horizontal (cosine) components cancel out...
  49. 1

    Discharging capasitors and it's general electrical propertie

    It's just that I've never properly sorted this confusion of mind, so i would like to sort it out so it 2 different capacitors are in series with a resistor: (let's say 0.15F, 0.45F, 150M ohm) 1. both current and voltage drops exponentially 2. capacitance on capacitors remain same over time? 2...
  50. Elvira

    Calculate the temperature based on Resistance

    Hello experts... I have an experiment pool boiling. The test section filled with DI water, and use thin flat copper as the heater that connected to the power supply. I want to ask how to measure or calculate the heater temperature if I only have the resistance, voltage and current data reading...