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. Moara

    Electric field of a charged cube

    Tried to use gauss law but there isn't any usefull symmetry that I have seen. Also tried to integrate the field due to small charges over the whole cube, didn't work too since the integral were too much complicated.
  2. callie123

    How easily can a high amperage electric fence be shorted out?

    Researching for a Scifi novel that depends heavily upon electricity...something I don't know much about! Any input would be appreciated! My situation: Somebody is trying to sneak through a high powered electric fence. Is it at all feasible to short out the fence somehow -- like, connecting it...
  3. A

    Acceleration of an electron due to Magnetic and Electric fields

    I figured that we would simply add up the forces acting on the electron (the electric force Fe and the magnetic force Fb) and then equate this to the given acceleration multiplied by the mass of the electron like so. vector Fe + vector Fb = (mass of electron) (vector acceleration) since vector...
  4. G

    Electric Dipoles: Convention & Field Lines

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

    Help with negative charges in an electric field.

    How can a negative charge move towards a position of a higher electric potential from lower potential but lose electric potential energy?From my understanding, I understand that for a positive charge, it must lose potential energy from the electric field as work is done by the electric force in...
  6. ybisno

    Given Electric field, find the charge densities

    Hi. Need help with physics homework. I was able to separate each term and find sigma from the second term and possibly lambda from the first term. Not sure how to approach the third term. (attached attempt at question)
  7. ybisno

    Given Electric Field, Find the charge densities.... (Electrostatics)

    Hi. Need help with physics homework. I was able to separate each term and find sigma from the second term and possibly lambda from the first term. Not sure how to approach the third term. (IMAGE ATTACHED)
  8. A

    Electric Potential across charging battery.

    Homework Statement [/B] A car battery with a 12v emf and an internal resistance of .040 ohms is being charged with a current of 50A. A.) What is the potential difference across the terminals? B.) The rate of energy dissipation in the battery Pr. C.) the rate of energy conversion to chemical...
  9. Shohel chowdhury

    Cancellation of the electric field from opposite charges

    Electric field of opposite charges, cancel out each other, is it right?
  10. fight_club_alum

    Uniform charge density and electric potential

    Homework Statement A charge Q is uniformly distributed along the x-axis from x = a to x = b. If Q = 45 nC, a = –3.0 m, and b = 2.0 m, what is the electric potential (relative to zero at infinity) at the point, x = 8.0 m, on the x axis? a . 71 V b. 60 V c. 49 V <-- correct answer d. 82 V...
  11. J

    Electrical Electric Hot Water Heater 2000 watt 220 volt run on 110 volt

    Will a hot water heater element that is rated 220 volt AC by 2000 watts when only applying 110 volt AC just put out 1000 watt instead?
  12. fight_club_alum

    Electric Potential slowing a charged particle to a stop

    Homework Statement A particle (mass 6.7 × 10–27 kg, charge 3.2 × 10–19 μC) moves along the positive x-axis with a speed of 4.8 × 105 m/s. It enters a region of uniform electric field parallel to its motion and comes to rest after moving 2.0 m into the field. What is the magnitude of the...
  13. W

    Working with Electric Field E, not Vector Potential A

    We commonly have E and B defined as: But how can I work in electric field E, instead of vector potential A?
  14. M

    Calculate number of turns for an electric heater

    Homework Statement Need to calculate, how many turns of nichrome wire do I need on a cylinder to make a heater with resistance of 40 Ω. Wire diameter = 1mm Cylinder radius = 2.5cm R = 40 Ω Wire diameter = 1mm Correct answer - 200 turns Homework Equations R = ρ*l/S R = resistance ρ = specific...
  15. M

    Calculate the energy in a capacitor's electric field

    Homework Statement Capacitor has a charge of 0.008C. Capacity is 2 μF. Need to calculate energy of electric field. Answer: 32J Homework Equations E = q2/2*C The Attempt at a Solution This seems right equation, but instead of 32J I get 16J.. any ideas?
  16. tinesi

    Voltage, electric field and potential energy for concentric shells

    1. Homework Statement the a shell is charged Va=120v shell b is grounded, Vb=0V What is the voltage in the center of shells (vo)? The electric field in the center of shells? The potential energy in the center of shells? Homework Equations Vr=Va+(1/r-1/a)/(1/a-1/b)Vab (from integrals) though I...
  17. solzonmars

    Electric field outside a spherical shell?

    If a charge is put inside a spherical shell, why is the electric field outside the shell independent of the location of the charge? Gauss's law could find that the net flux is independent, but not each individual field? Is this something about the surface charge density being independent of...
  18. S

    Electric resistivity and friction

    In the situation of a magnet moving towards a flat sheet of copper; why doesn't the copper gain angular moment as the electrons move in concetric circles? The electrons are experiencing friction as they move through the copper.
  19. J

    Can Electric & Magnetic Fields Coexist?

    For light it is said it has no volume and also it it waves of electric and magnetic field. But for electric and magnetic field you need space? So can they both be at the same time?
  20. H

    The effect of an external substance on the electric force between two charges

    How does the force between the two opposite charge change if we place a substance (conductor, insulator, ...) between them? It seems that the force between the two charges doesn't change but the total force on each charge increases because of the superposition of the original field of the other...
  21. A

    What is the electric field of a point charge?

    Assuming the point charge lies at the origin, what is the electric field at the origin? Zero or undefined?
  22. JD_PM

    Average electric field over a spherical surface

    Homework Statement I was working out problem 4, chapter 3 of Introduction to Electrodynamics by Griffiths: a) Show that the average electric field over a spherical surface, due to charges outside the sphere, is the same as the field at the centre. b) What is the average due to charges inside...
  23. 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...
  24. A

    -qEx for a vertical spring in a constant Electric field

    A massless spring of spring constant k = 13 Newtons per meter hangs purely vertically. A 20 Newton, 5(10-3) Coulombs charged particle is attached to the spring and released from rest. Besides all this, there is also a constant, external Electric Field of 9000 Newtons per Coulomb pointing...
  25. Boltzman Oscillation

    I GR: Electric & Magnetic Effects - Consequences

    So I just learned that in general relativity Magnatic and Electric fields are dependent on the observer. What are some consequences as a result?
  26. L

    What Is the Magnitude of the Electric Field Between Parallel Plates?

    Homework Statement An electron is projected with an initial speed v0 = 4.65×106 m/s into the uniform field between the parallel plates in (Figure 1). The direction of the field is vertically downward, and the field is zero except in the space between the two plates. The electron enters the...
  27. D

    Calculate Electric Potential from Non-uniform Linear Charge

    Homework Statement "A rod of length L lies along the x-axis with its left end at the origin. It has a non-uniform charge density λ=αx where α is a positive constant. a) What are the units of α? b) Calculate the electric potential at A. Homework Equations Linear charge density: λ = Q/L where Q...
  28. CharlieCW

    Finding electric potential using Green's function

    Homework Statement We have two semi-infinite coplanar planes defined by z=0, one corresponding to x<0 set at potential zero, and one corresponding to x> set to potential ##V_0##. a) Find the Green function for the potential in this region b) Find the potential ##\Phi(r)## for all points in...
  29. H

    Electric arc: How to calculate the required voltage for a light bow?

    <Moderator's note: Moved from a homework forum.> Calculate the required voltage to produce a electric arc between 2 iron nails (distance: 3cm). I´ve read in the internet that you need 1 kV per mm. But how can I calculate this value, that I need 1kV per 1mm?
  30. J

    Electric Potential and Field Diagram - True/False

    Homework Statement Four charges are arranged at the corners of a square as shown in the figure. Q1 is at (-L/2,L/2), Q2 is at (L/2,L/2), point a is at the origin and Q1=Q2=-Q3=-Q4. Which of the following statements correctly describe the electric field E and the potential at points a,b and c...
  31. M

    Electric Fields from Linear Charges

    Homework Statement Am amount of charge Q is uniformly spread over a semi-circle of radius R whose center is located a distance A from the origin. What point charge would have to be placed at the origin so that the E field at the center of the circle is 0? (The open end of the semi-circle is...
  32. D

    Dependence of an electric field on distance

    Homework Statement A proton located several proton diameters away from a small charged object carrying charge q is subject to an electric field of magnitude E. As the proton moves a distance d along the x-axis away from the object, the electric field magnitude drops to E/4. If the charged...
  33. martinbandung

    Calculating Electric Field at Point A from Uniformly Charged Arc

    Homework Statement Find electric field at Point A its an arc with uniform density= lamda https://drive.google.com/file/d/14cBqE2dMe_w0nb9LtPG0h1cUOrzGWt6g/view?usp=sharing the problem Homework Equations E=intergal dq/r^2 The Attempt at a Solution I've tried using wolfram and cosine rule to...
  34. J

    Batteries and the electric field inside a wire

    I have a question what does create a electric filed inside coducting wire? And is it the same field trought the whole wire? Thanx for answers.
  35. Mutatis

    Find the electric field at an arbitrary point

    Homework Statement A distribution of charge with spherical symmetry has volumetric density given by: $$ \rho(r) = \rho_0 e^{ \frac {-r} {a} }, \left( 0 \leq r < \infty \right); $$ where ##\rho_0## and ##a## is constant. a) Find the total charge b) Find ##\vec E## in an arbitrary point...
  36. ino

    Find the electric field at the point P on a right triangle

    Homework Statement https://www.physicsforums.com/threads/find-the-electric-field-in-the-point-p-of-a-right-triangle.965285/#post-6125768 knowing that the three charges are equal and that the angles of the triangle are 90°, 45°, 45°. Homework Equations The Attempt at a Solution I tried...
  37. german_cargo

    Need motor help with Electric Power Brush project for clearing snow

    I'm in the snow removal business and am unhappy with my snow plow on residential driveways. I am going to fabricate a light duty power brush for my vehicle, and I am going to power it with an electric motor and battery pack for quiet operation and relative simplicity. The demands on this power...
  38. Zack K

    What Is the Electric Field of a Curved Rod at the Origin?

    Homework Statement A rod of charged -Q is curved from the x-axis to angle ##\alpha##. The rod is a distance R from the origin (I will have a picture uploaded). What is the electric field of the charge in terms of it's x and y components at the origin? k is ##\frac {1} {4\pi \epsilon_0}##...
  39. A

    Does the distance between substations affect the efficiency of electric trains?

    Every time I take a train I sort of think about this, so the electrified overhead wire (DC or AC) and the rails form a transmission line and the train is a load that moves along the transmission line. Let's talk about the DC case as it seems more simple, so when the train is at or near a...
  40. S

    Electric field at a point problem

    Homework Statement In the figure above, charge A is -5.00 nC, charge B is 10.0 nC, and charge C is 5.00 nC. If x = 2.10 cm and y = 4.20 cm, what is the electric field at the dot? Homework Equations E = kq/r^2 The Attempt at a Solution r = distance from A to point = sqrt(x^2+y^2) Ea = kq/r^2...
  41. J

    Theoretical models of the Earth's Electric Field?

    I am doing some research into atmospheric energy harvesting. To design a proper feasibility experiment, I need to establish some theoretical baselines. I see a lot of values for the field strength for example, tossed about from various papers. However, there does not seem to be a standard...
  42. C

    Find the electric field of a point outside sphere

    Homework Statement Find the electric field of a point outside sphere without using Gauss's law. (Do not evaluate the integral) Homework Equations Coulomb's Law Spherical Co-ordinate System The Attempt at a Solution I have attached my attempt as a picture but now I am stuck, I don't know how I...
  43. C

    Heating Effect of Electric Current-Transmit at High Voltage

    Homework Statement Why is it inefficient to use low voltage when transmitting electricity? Homework Equations P∝i2 P=Vi H=Vit P=Ri2 E/ti2=V/i These are all basically the same few formulas, but I wrote down all iterations of them. Anything from Joule's Law/Joule Heating The Attempt at a...
  44. J

    I Falling electric dipole contradicts the equivalence principle?

    Consider an electric dipole consisting of charges ##q## and ##-q##, both of mass ##m##, separated by a distance ##d##. If the dipole is given an acceleration ##a## perpendicular to its moment the total electric force on it, due to each charge acting on the other, is given approximately by...
  45. Zack K

    Change in the Electric Field Due to a Copper Wire Being Inserted

    Homework Statement A point charge of 6 × 10−9 C is located at the origin. The magnitude magnitude at ##\langle 0.6,0,0\rangle## m is 150 N/C Next, a short, straight, thin copper wire 5 mm long is placed along the x axis with its center at location ##\langle 0.3,0,0 \rangle## m. What is the...
  46. PainterGuy

    Electric field outside a parallel plate capacitor

    Hi! Could you please help me with the queries below? Thanks a lot. Question 1: My question is about the field outside the plates of parallel plate capacitor. It is said that the field(s) between positively and negatively charged plates gets added up but the field(s) outside the plates gets...
  47. Zack K

    Magnitude of an Electric Field due to a dipole

    Homework Statement A dipole is located at the origin, and is composed of charged particles with charge +e and -e, separated by a distance 2x10-10m along the x-axis. Calculate the magnitude of the electric field due to the dipole at location ##\langle 0.2\times 10^{-8}, 0, 0\rangle##m Homework...
  48. lawlieto

    I How can ΔJ = 0 for an electric dipole transition?

    Consider a multi-electron atom. (In our course we deal with alkalis mostly so that we have energy levels which are similar to the hydrogenic ones with quantum defect. I don't know if that is relevant here) Edit: l = orbital angular momentum of a single electron, L = total orbital angular...
  49. 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...
  50. I

    Model electron movement in an electric field (Magic Eye tube)

    Hello there, I'd like to model a simplified version of a "Magic Eye" tube (e.g. without the amplification triode, and for a start, 2 dimensions only), or the visible display behavior. What I'm talking about: https://en.wikipedia.org/wiki/Magic_eye_tube#Operation Here is a nicer depiction of...
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