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. H

    Determining electric field using gauss's law--different distributions

    These are the 4 distributions shown, and I have to determine which two distributions (or none at all) can use Gauss's law to determine the electric field. So electric flux = EA = Q/electric constant. Since all of them have charges, I could do something like Q/(A*electric constant) to get the...
  2. naviakam

    I Estimating Particle Number in an Electric Field

    In an electric field ##E## if the energy of charged particle (ion) is formulated as ##W=qEr## where ##r## is the distance, how the number of particles is estimated?
  3. Fikremariam

    Electric Field -- Potential between the ends of a 2 meter stick

    I tried to find the charge from the formula v=k q/r and apply it to find the field but couldn't be sure
  4. robphy

    Insights The Electric Field Seen by an Observer: A Relativistic Calculation with Tensors

    Continue reading...
  5. P

    Work done by electric field to move capacitor plate

    so the result I got is the energy lost by the field right??
  6. P

    Problem on induced electric field, electrodynamics

    The problem is shown above, the hint to solve the problem is below. See the hint if it is difficult for you to imagine what is going on. I am assuming the diagram in the hint shows what's happening when the mass is falling at terminal velocity. I have quite a few questions. 1. How do the wheels...
  7. T

    Electric field inside a charged ring

    I am just a bit confused here. Would doing this even change the electric field direction at the center at all? I'm thinking no, but a bit of direction would be appreciated. This problem is really simple, I'm just a bit confused.
  8. A

    I Electric Field seen by an observer in motion

    In Robert Wald's General Relativity textbook page 64 reads: __________________________ In prerelativity physics, the electric field ##\vec{E}## and magnetic field ##\vec{B}## each are spatial vectors. In special relativity these fields are combined into a single spacetime tensor field ##F_{ab}##...
  9. J

    Electric Potential of point outside cylinder

    Edit: Below is my work but i believe i have chosen the wrong values of the separation vector in the s direction. Any ideas as to what it should be?
  10. E

    4 (insulated) wires from electric pole for underground 3-phase service

    Hi all. This is probably a simple question, but I am hoping for some guidance on why a service would be delivered with 4 wires as seen in the image. It appears fairly common around here (northeast U.S.), if not standard, for one of the phase-conductors to be 'double-tapped' and go underground...
  11. F

    Billing System for Electric Vehicle

    Summary:: How to form an automatic billing system through Bluetooth and mobile phones? For commercial purposes, how can my system automatically signal, calculate the billing value and actually perform the billing or transfer the transaction from a credit or debit card or a bank account? [Note...
  12. T

    POTENTIAL DIFFERENCE AND ELECTRIC FIELD HOMEWORK

    I tried following the formula but it wasn’t correct. I’m sure I could get it if I had an example as I’m sure this must be a simple question for other people I was just unsure if I was doing it correct.
  13. Ibby321

    Vertical motion through an electric field

    I know that the answer is 0 J (no NET work was done) because there is symmetry to the problem and this symmetry comes from the fact that the direction of force changes, BUT I don’t know why the force changes (I have an idea; TBD below in #4). When I did this problem I thought I could find the...
  14. I

    Electric Field from a Charged Semicircular Rod

    Charge QQ is uniformly distributed along a thin, flexible rod of length LL. The rod is then bent into the semicircle shown in the figure (Figure 1).Find an expression for the electric field E⃗ E→ at the center of the semicircle. Hint: A small piece of arc length ΔsΔs spans a small angle...
  15. Costweist

    Changes in electric field lines as a result of an oscillating charge

    The last couple of days I’ve been troubled with a specific part of electromagnetism. How will electric field lines be affected by an oscillating charge? More specific, what will happen with the “amplitude” of a wave in an electrical field line as the wave propagate away from the charge? 1. Will...
  16. B

    How to create an Electric Field?

    Dear friends, First of all I have one question! As per Figure 1, how to implement electrical connection in real life which are seen inside Red Box? and what is the meaning of grounding the other terminal? Figure 1 And the second thing is that, I want to create and electric field on copper...
  17. H

    Question about the force exerted by a uniform electric field on a dipole

    I think the answe should be C as shown in the attachment.
  18. S

    Electric Charge is basic property of matter or subatomic particles ?

    In some textbooks it is given that - Electric charge is the characteristic property of matter that causes it to experience a force when placed in an electromagnetic field. and In other textbooks it is given that - Electric Charge is the property of subatomic particles that causes it to...
  19. S

    Fourier transform of electric susceptibility example

    I have not studied the Fourier transform (FT) in great detail, but came across a problem in electrodynamics in which I assume it is needed. The problem goes as follows: Evaluate ##\chi (t)## for the model function...
  20. D

    Deriving electric and vector potential

    1- Write down the complete MAXWELL equations in differential form and the material equations. 2- An infinitely extensive area is homogeneously filled with a material with a location-dependent permittivity. There are charges in the area. Give the Maxwell equations and material equations of...
  21. V

    Relationship between electric and magnetic fields

    So, basically I can follow the math deriving E/B = c from Maxwell. And I can calculate B and H from I: H = I/2*pi*r and B=uH. Easy. So, for example I take a 2000 A, 50 Hz, current and a distance of 2 meter from that current in a round conductor. H and B are set: H = 160 A/m and B = 0,2 mT...
  22. F

    Understanding the Electric Field of Two Spheres: A Scientific Approach

    I am not quite sure how to present my answer in the form of a function with relation to the distance from the centre. What I got so far is the E1 and E2, for the internal and external sphere respectively. For internal sphere, the charge is volume * 𝜌, so it is $$ \frac{4\pi r^{3}}{3} * 𝜌$$...
  23. B

    Energy within an electric field

    I am trying to calculate the energy within an electric field that is generated between two plates by a pulse but am unsure of what voltage value to use. The pulse is a sinc wave. I am assuming I can still use the equation ## E= \frac{1}{2}CV^2 ##. I know the ##V_{rms}## and ##V_{max}## which...
  24. F

    Finding Electric field E due to an arc

    I need to account for tension, weight, and repulsion. For the tension, I can draw the x and y component of Tmax and see that the x components of the 2 tensions Tmax will cancel out, and there are 2 y components of the Tmax to factor in. Weight is just F = mg, where g is acceleration due to...
  25. naviakam

    Black body radiation vs electric discharge in a gas

    Black body radiation formula contains power and exponential terms. Electric discharge in a gas results in the ion acceleration; the ion distribution comprises power and exponential terms too. Any connection between these two phenomena (i.e. black body and potential) could be established?
  26. A

    Electric Field Shielding: Does a Conductor Shield Inside?

    Hi. I was reading about conductors in electrostatic equilibrium and how it makes sense that they have zero electric field inside the material even when an external charge is brought near. The charge density of the material just rearranges itself to cancel. Then I searched for hollow conductors...
  27. F

    Magnetic and electric fields in relativity

    I started from: $$\frac{d}{dt}(m\gamma v_x)=qE\ \ \ \rightarrow \ \ \ m\gamma v_x - p_{0x}=qE(t-0)\ \ \ \rightarrow \ \ \ m\gamma v_x=qEt+p_{0x} $$$$\frac{d}{dt}(m\gamma v_y)=0\ \ \ \rightarrow \ \ \ m\gamma v_y -p_{0y}=0\ \ \ \rightarrow \ \ \ m\gamma v_y = p_{0y}$$$$\frac{d}{dt}(m\gamma...
  28. Kaguro

    Concept of electric field and hollow conductors

    I think: Due to charge q, there will be a field in region 1, very much dependent on position of q. The inner surface charge density of irregular conductor is also dependent on the position( so that it could cancel the field of charge and E=0 inside body of irregular conductor). The outer...
  29. M

    Electric field of non-conducting cylinder

    a) I have calculated (1) λ = ρA = ρπr^2 = 2.49 * 10^-10 C/m and placed it into (2) yielding E = λ / (2πεx^2) = 106.73 N/C. This doesn't seem to be correct by the feedback, however. b) Here just to consider the proportion of the cylinder mass constrained by y.
  30. sep1231

    Electric Field as potential gradient

    I know that the electric field is directed from Q to P, but I'm not sure which magnitud is greater, I tried this
  31. F

    Lorentz transformations for electric and magnetic fields

    Good evening, I'm trying to solve this exercise that apparently seems trivial, but I wouldn't want to make mistakes, just trivial. Proceeding with the first point I wonder if my approach can be correct in describing this situation. From the assumptions, the two fields are in this...
  32. F

    Battery Powered Electric Motor and Charging Requirements

    I need to build a battery system to drive a 10 HP pump motor. The actual BHP varies as the pressure in the system rises, but for the most part we are operating at a 10.1 brake horsepower. Run time requirements will vary from a few hours to many hours. I settled on 8 hrs as a basis. Motor...
  33. TechieDork

    Find an expression for a magnetic field from a given electric field

    Here this is my attempt : Reference Textbook : Zangwill's Modern Electrodynamics I stuck at the last step , I really have no idea what to do next.
  34. A

    Finding a good descriptive model of the electric circuit (for 8th graders)

    Since this quesstion popped up in this thread I thought it might be better to create a new thread: https://www.physicsforums.com/threads/a-question-about-an-electrons-movement-in-a-dc-circuit.997736/ The question is the following: What kind of descriptive model could/should one use while first...
  35. A

    Electric Field from Non-Uniformly Polarized Sphere

    Solving for the volume and surface bound charge densities was easy using equations 1) and 2). The polarization only has an r component so ##ρ_b=-\frac 1 {r^2} \frac {d} {dr} (r^2 \vec P)=-α(n+2)r^{n-1}##, and ##\hat n=\hat r## so ##σ_b=αa^n##. To find ##\vec E## I intend to use equation 3)...
  36. PhysicsTest

    To find the parameters of velocity in an electric field

    i have drawn the E field as below, hence the F will be in the upward direction for electron a. Using energy is constant, the velocity ##v_x## as it crosses A is ##0.5mv_x^2 = q*V_a## ##v_x = \sqrt{(\frac{2qV_a} m)} m/s## one doubt i have here is, the question mentions electrons, but i have...
  37. A

    Who invented electric potential and why?

    Why was that concept necessary ?, I know there's also a gravitational equivalent of this concept I couldn't find anything on google Thanks Daniel
  38. badluckmath

    Electric Field of two line charges

    I'm trying to solve this, but i don't really know how to start this problem. There are two line charges and i must find the E. Field on the center.
  39. J

    What effects does an electric field have on potential energy?

    Like an electric field is applying a sort of force on a particle. I was wondering if this at all impacts the potential energy of a particle. For instance, when the force of gravity does work on an object, its potential energy changes as a consequence. Would it be the same thing here?
  40. S

    Converting a Lawn Tractor to Electric Power

    So I am converting an old gas lawn tractor to electric. I have a 48v 2000w motor to drive the axle. For the deck, I sourced two 40v old Ryobi deck motors (I don't have them yet). Since my power supply will be a 48v lithium battery, I wanted to run the two deck motors off the controller running...
  41. PhysicsTest

    Find the electric field from charge density

    There is a section in the BJT explanation the charge density and the corresponding electric field graphs. But i was not sure how the electric field is derived and hence i started deriving it. Please correct me if my understanding is wrong in posting the question It is an ##npn## BJT. My...
  42. B

    Understanding the electric field of a sphere with a hole

    Here's an image. O and O' are the respective centers, a is the distance between them, r is the distance from the center of the sphere to P, and r' = r - a, the distance from O' to P. The approach (which I don't understnad) given is to use Gauss' Law and superposition, so that we calculate the...
  43. greg_rack

    The electric field between two adjacent uniformly charged hemispheres

    here is the situation Hi guys, I should illustrate the motion of an electron in both cases, but I cannot really understand how will the field be like in the gap between the two(filled) hemispheres(conductor and non). Another thing is: for the conductive hemispheres, does it make any sense to...
  44. Kaguro

    Poynting vector and electric field

    The Poynting vector $$\vec S=\frac{1}{\mu_0} \vec E \times \vec B$$ gives the power per unit area. If I need this in terms of electric field only,I should be able to write B=E/c (for EM wave) Assuming they're perpendicular, ##S =\frac{1}{\mu_0 c}E^2##. Now, ##c=\frac{1}{\sqrt{\mu_0 \epsilon_0}}...
  45. PhysicsTest

    Power Calculation of general electric circuit

    I am trying to calculate the power calculation of a general circuit with voltage leading the current by a phase difference of ##\theta##. The instantaneous voltage is given by ##v = V_m\sin(\omega t +\theta) ; i = I_m\sin(\omega t) ##. The instantaneous power is then ##p = V_m I_m \sin(\omega t...
  46. greg_rack

    What is the physical significance of torque being a vector in an electric motor?

    Hi guys, In my head, torque has also been associated with a bare SCALAR physical quantity given by the formula ##torque=rFsin\theta## which caused a rigid body to spin around its axis. Now, studying magnetism, I find out that torque is a VECTOR, which magnitude is indeed given by ##rFsin\theta##...
  47. P

    Electrostatics - electric potential and field strength (dielectric)

    Could somebody check my solution?
  48. R

    Electric Fields with Motional EMF

    Suppose I have a wire loop that I am moving away from a very long wire which carries a current upward and I want to find the induced current in the loop. The way I know how to approach this is with either Faraday's Law or motional EMF. My question concerns the motional EMF approach. My...
  49. A

    Electric Circuit: Path of Least Resistance

    I figured that when you close the switch the current from the upper cell will travel through the closed switch due to it being the path of least resistance, essentially the resistor between cells is unused (was my first thought). I'm not entirely sure how to progress with this question.
  50. G

    Find the electric field from polarization

    Attempt at solution: a) Since I need help with b) this section can be skipped. Results : ##ρ_{psa} = -Pa ## ##ρ_{psb} = Pb ## ##ρ_{p} = \frac {-1}{R^2} \frac {∂(R^2PR)}{∂R} = -3P ## b) This is where I am unsure (first time using gauss law for P) so I need some confirmation here: ## \int...
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