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. J

    Electric and Magnetic field acting on an electron

    Homework Statement In the figure, an electron of mass m, charge − e, and low (negligible) speed enters the region between two plates of potential difference V and plate separation d, initially headed directly toward the top plate. A uniform magnetic field of magnitude B is normal to the plane...
  2. J

    What happens to the current when an electric motor slows to a halt?

    If a motor slowed to a halt, will the current go up or down
  3. L

    Calculate the charging time for my Electric Vehicle

    So cars usually specify the batteries in kWh (rather than Ah). So given that i know the kWh capacity of a car. I also know the charging effect in W (i.e. the voltage and amps in my charging station). Can I reasonably estimate the time it'll take to charge the battery? It doesn't have to be...
  4. Physics Dad

    Finding the electric field of insulated shell

    An insulating spherical shell of inner radius r1 and outer radius r2 is charged so that its volume density is given by: ρ(r) = 0 for 0 ≤ r < r1 p(r) = A/r for r1 ≤ r ≤ r2 p(r) = 0 for r > r2 Where A is a constant and r is the radial distance from the center of the shell. Find the electric...
  5. Jozefina Gramatikova

    Conducting sphere Find the electric filed for r<a,a<r<b,r>b

    Homework Statement Homework Equations The Attempt at a Solution for part ii) a<r<b E=0 I am not sure what will be the difference between the formulas for the electric field for a<r and a>b I think the formulas will look the same: The only difference that I can think of is that when r<a...
  6. A

    Electric field distribution in the brain

    I have a PhD in Molecular Neuroscience but am working on something that requires knowledge of electric field distribution in the brain. I understand that electric field intensity (V/cm) is E=(V1-V2)/d in a theoretical model (between 2 infinite plates, that are parallel and equidistant through a...
  7. D

    Electric Field of a Non-Uniformly Charged Sphere | Homework Help

    Homework Statement A solid isolated sphere with radius R has a non uniform charge which is given by ρ= Ar², with A a constant and r<R measured from the centre of the sphereHomework Equations (a) Show that the electric field outside the sphere is equal to E = (AR5)/(5ε0r²) (b) Show that the...
  8. R

    Complete screening of an Electric field?

    Hi, I have difficulty understanding the term screening. Screening is reducing of the electric field, as far as I have understood until now. 1. Why does screening occurs? Is it due to collective interaction of plasmons? 2. If we have a slow electric field, will screening occur or will it not...
  9. S

    Electric displacement field

    Hello, I'm going through electrodynamics by griffiths.. I'm unable to understand the case 1) for no free charge and 2)when curl of P(polarisation ) is zero at the boundary Then what can we comment about D the displacement field having both it's divergence and curl zero at the boundary. Please...
  10. Krushnaraj Pandya

    Potential difference in uniform electric field

    Homework Statement There is a uniform electric field=100 V/m inclined at 45 degrees with the x axis. My doubt boils to which is greater? V(0,0) or V(10√2,0) (since my answer has the wrong sign) Homework Equations All electrostatics formulas The Attempt at a Solution The work done to move a...
  11. Krushnaraj Pandya

    Electric field and potential at vertex of cube

    Homework Statement A solid non-conducting cube of side l and uniformly distributed charge q, has electric field E and potential V at one of its vertex, imagine this cube to be made of 8 smaller cubes of side l/2. if one such cube is removed, find the new field and potential at the point where...
  12. Mirza Danish Baig

    Electric field between conducting and non-conducting sheets

    Homework Statement Two infinite sheets of charges are placed parallel to each other. If the sheet on the left is non conducting and have a uniform charge density 3(sigma) and the one on the right is conducting and has a uniform charge density (sigma). If the area on both plates is 1m^2 then...
  13. Muhammad Usman

    Capacitor Electric Field in a Dielectric?

    Hi, I was reading the capacitor and its operation and it is written there that when the DC is applied to the capacitor it becomes open circuit. The main mechanism behind this phenomena is explained as below:- "When DC voltage is applied the charge started accumulating on the plates of the...
  14. S

    Fundamental confusion about THREE-PHASE electric power setup

    Homework Statement Hello to everyone who's reading. :) I hope I posted this in the right place; while this is not exactly a homework problem, I am trying to improve my understanding of the background information before proceeding with course-style problems. This post is because I'm trying to...
  15. F

    Basic question about current in an electric circuit

    Let's say we have a basic electric circuit consisting of a battery with some potential difference, and a loop of wire. The wire loop also has some segment with a higher resistance. Now since there is a potential difference, the free electrons will move to make the circuit equipotential. The...
  16. shahbaznihal

    Spatial dependence of induced Electric field

    The Faraday's law and Lenz's law together give you, $$\xi = -\frac{\partial\phi_B}{\phi t}$$ or put another way,$$\vec{\nabla} \times \vec{E} = -\frac{\partial \vec{B}}{\partial t}$$. My question, I am just asking to make sure, the spatial dependence of ##\vec \nabla \times \vec E## will be the...
  17. 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...
  18. D

    Why electric field is always perpendicular to equipotential?

    I have some understanding, but I'm not sure about how accurate it is: Electrostatic force is given by F = qE, where F and E are both vector quantities. If the dot product of either side and the displacement vector Δs along an equipotential line is taken, the equation becomes F⋅Δs = qE⋅Δs. F...
  19. J

    B Electric Field in Accelerating Elevator

    According to an inertial observer the electric field of a charged ball sitting on the floor of an accelerating elevator is contracted more than the elevator is contracted. So the inertial observer concludes that an observer inside the elevator will measure that the Coulomb-force from the ball is...
  20. S

    Is Griffiths' formula for electric dipole radiation correct?

    Hello! I am reading Griffiths derivation for the electric dipole radiation (actually my question would fit for the magnetic dipole radiation too). He considers 2 charged balls connected by a wire with charge going back and forth between them. Now, when he calculates the vector potential he uses...
  21. M

    Electric racing -- Custom 4WD Electric Race Car Advice Please

    [Mentor's note: two threads on the same topic have been merged] I live here in Stephenville, TX and currently going to Tarleton for Civil engineering. A bit rusty and new to electrical components. But anyways, here in town lawnmower racing is kind of a big event. Many of us have 600cc crotch...
  22. 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...
  23. A

    Electron speed and acceleration in an electric field

    Hi everyone, I often work on a SEM, a type of microscope which is based on electron acceleration between an electron source and the sample you are working on. For this reason and since a few weeks I was wondering how an electron (in term of speed) behaves in a constant and linear electric field...
  24. Zahid Iftikhar

    Electric Potential midway between a pair of equal opposite charges

    Hi I need help to understand how electric potential could be zero at the center of two equal but opposite charges. It seems, there is a no field free region anywhere inside the space between the charges. If I move a test charge from negative to positive charge or otherwise, there seems to be no...
  25. José Ricardo

    Understanding Electric Car NOS to How it Works

    How works a "NOS" of a electric car?
  26. A

    Changing electric field generating magnetic field

    I would very much appreciate a clarification on what is meant by a changing electric field in the context of statements such as 'a changing electric field creates a changing magnetic field'. My question is does the electric field actually need to reverse as a lot of examples show where two...
  27. M

    Work in a uniform electric field

    I need a little help here when calculating the work done in a uniform electric field on a positive charge to move it from point a at higher potential to point b at lower potential that means the charge is going towards the negative plate we first use V = - ED and then we have a...
  28. T

    An electric current in a wire occurs when....

    An electric current in a wire occurs when... A. electrons move in the wire as a result of getting pushed along from a neighboring electron. B. electrons move in the wire as a result of the repelling force from the negative battery terminal and the attractive force from the positive battery...
  29. Z

    Electric Field Outside of a Ring of Charge in the X-Y Plane

    If I try to calculate the electric field in the x-y plane of a ring of charge resting at the origin on the x-y plane, I keep getting zero. I start with Coulomb's Law. $$ dE(r) = \frac{1}{4\pi\epsilon}\frac{dq}{r^2} = \frac{\lambda R}{4\pi\epsilon}\frac{d\theta}{r^2},$$ in which ##\vec R## is...
  30. S

    Why is Electric Field Below an Infinite Plane 0? Exploring Griffiths' Result

    Hello! I am reading about image charges for an infinite plane and a charge above the plane. In the book I am reading (Griffiths) the author says (and uses this results several times) that the field below the plane is 0. How do we know this? The method of the mirror charges gives the V above the...
  31. A

    Electricity and Magnetism Electric Field Problem

    1. Problem Statement: Find positions on the x-axis for the charges Q1 = -1 C and Q2 = +3 C so that the electric field is zero at x = 0. Homework Equations :[/B] I'm thinking I need to use Coulomb's law for this one. I'm just having trouble figuring out where to start. Coulomb's states E=kQ/r^2...
  32. CDL

    Electric Flux through the Face of a Cube

    Homework Statement Griffiths' Introduction to Electrodynamics problem 2.10, Homework Equations Gauss' Law, ##\int_{S} \textbf{E}\cdot \textbf{dS} = \frac{Q_{\text{enc}}}{\epsilon_0}##[/B]The Attempt at a Solution It seems reasonable that the flux through the shaded surface and the front...
  33. 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...
  34. P

    Magnitude of the electric field at equator (measured in kV)

    Hi there Only known variables include the solar flux on the Earths atmosphere at the equator is 1.5 kWm^ -2. I've calculated the total energy from the Sun as 4 x 10^26 W, but can't seem to get to a calc of the mag of electric field at equator (measured in kVm^-2).
  35. A

    Quantum Field Theory. Electric discharge

    How work triboelectricity in QFT? Materialists exchange electrons as well as in classical theory?
  36. M

    How to Implement Piecewise Time-Varying Electrode Surface Potential in Comsol?

    Can anyone know please know how can i impose the electrode surface potential to vary lineary and periodically with time as: E(t)= phimin+v*t for 0<=t<t0 phimax-v*(t-t0) for t0<=t<2*t0 with t0=(phimax-phimin)/v v=scan rate in V/s
  37. Zubair Ahmad

    Electric Potential: Griffith's Electrodynamics Ch.2 Ex.7 Explained

    In Griffith's electrodynamics chapter 2 example 7 he calculates potential due to a spherical shell outside it. Here E is radially outward while dr is radially inward as we are going towards the sphere hence E.dr should be negative but it is taken positive?
  38. C

    Calculating Electric Potenial Difference

    Homework Statement In a TV tube, an electric potential difference accelerates electrons from a rest position towards a screen. Just before striking the screen, the electrons have a wavelength of 1.0 x10-11m. Find the electric potential difference.[/B] Homework Equations λ = h/mv Ek = qΔV The...
  39. N

    Electric Potential Difference Problem

    Homework Statement Two charges, A (-3 C) and B (+4 C), are placed 2.40 m apart. Point X is 30 cm from A, and Point Y is 30 cm from B. What is the electrical potential difference going from X to Y? Homework Equations W = △Vq The Attempt at a Solution Teacher gave answer as 6.9 x 10^4 V I am...
  40. G

    Skin effect and electric shock question

    recently i saw a thread where skin depth was mentioned (I guess in one of my own threads) and then it got me thinking, well imagine we have a rather thick wire thick enough so that for a given frequency there is almost no current running in the middle of the wire due to skin effect. let's take...
  41. A

    How Is Electric Potential Difference Measured Without Specific Distances?

    Hello, I'm struggling to understand how the electric potential difference is measure especially when a distance is not given. For instance in Serway, on the explanation of the Van de Graaff Generator the authora write, "Van de Graaff generators can produce potential differences as large as 20...
  42. A

    Finding Equilibrium in Electric Fields of Two Charges

    Homework Statement An electric field is created by an uniform linear charge with a linear charge density is 40 nC/m. Find the potential difference between the two points, one of which is situated 5 cm from the line charge and the second at 10cm. Two charges, q and -3q, are situated at a...
  43. J

    Electric Potential of a Sphere at Different Locations

    Homework Statement A solid insulating sphere of radius a = 3.6 cm is fixed at the origin of a co-ordinate system as shown. The sphere is uniformly charged with a charge density ρ = -215 μC/m3. Concentric with the sphere is an uncharged spherical conducting shell of inner radius b = 11 cm, and...
  44. H

    Find the scalar value and direction of the electric field

    Homework Statement Two charged balls are placed in point A and B and the distance between them is 9,54cm. Each of the balls are charged with 8,0 x 10^-8 C. Find the scalar value and direction of the electric field in point C placed 5 cm from A and 6 cm from B. Homework Equations Cosine Rule...
  45. M

    How Do Electric Potential, Potential Energy, and Work Interact in Physics?

    Hello, I have a question on electric potential, potential energy and work. ##\Delta V = \frac{\Delta U}{q_o}## ##W = q_o\Delta V## ##W = -\Delta U## Example: A point A that is closer to the source charge than point B, then the electric potential difference is negative (##\Delta V = V_B -...
  46. H

    Electric Force on a Charge in a Solenoid

    Homework Statement [IMG]http://[url=https://ibb.co/dgUy6T]https://preview.ibb.co/iyqS0o/20180525_213806.jpg Since i only know the field direction, increasing go into page. Why the answer is C? Why the answer "a" ? The R and r on the pic is respected to what? Homework EquationsThe Attempt...
  47. C

    Work done per unit charge by electric field on charge

    Homework Statement Homework EquationsThe Attempt at a Solution I know the units for V is J/C so #3 and #4 are wrong. But how do I determine the signs?
  48. S

    What is the electric charge on the charged polystyrene ball?

    Homework Statement A charged polystyrene ball of mass 0.14g is suspended by a nylon thread from a fine glass spring. In the absence of any electric field the spring extends by 30mm. The polystyrene ball is then placed in an electric field that acts vertically upwards, of strength 200kV m^-1...
  49. T

    What is the direction of the electric field inside a battery?

    Outside the battery, in the conductor it is in the direction of conventional current. But what about inside? Since magnetism and electricity are related, and magnetic field inside a magnet is from South to North (outside it is North to South), i doubted for any correspondence.
  50. prodo123

    (General question)Area charge density and electric potential

    Homework Statement Sorry, the post isn't about a single homework problem but rather something that I keep getting confused on. It's about calculating the electric potential of a spherical shell of uniform charge in two different ways. Homework Equations ##\Delta V=\int_a^b -\vec E\cdot d\vec...
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