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. G

    Electric field due to semi-circular wire at a distance

    Homework Statement A semi-circular wire containing a total charge Q which is uniformly distribute over the wire in the x-y plane. the semi-circle has a radius a and the origin is the center of the circle. Now I want to calculate the electric field at a point located on at distance h on the...
  2. Physics Dad

    Find the total electric charge in a spherical shell

    Homework Statement Find the total electric charge in a spherical shell between radii a and 3a when the charge density is: ρ(r)=D(4a-r) Where D is a constant and r is the modulus of the position vector r measured from the centre of the sphere Homework Equations Q=ρV Volume of a sphere =...
  3. G

    Electric field in a capacitor with a dielectric

    Homework Statement A parallel plate capacitor has 2 square plates of side l, separated by a distance d (l is a lot bigger than d). Between the plates, there is a linear and non-homogeneous dielectric with constant $$\epsilon_R=1+ay$$ with $$a$$a positive constant. Calculate the electric field...
  4. K

    Electric Field and Kinematic Equations for Acceleration and Time Calculations

    Homework Statement Homework Equations F=qe, a= qe/ma, x= vit + 1/2t^2 The Attempt at a Solution (a) i used the formula a= qe/ma to calculate the acceleration and then substituted in this kinematic equation x= vit + 1/2t^2 then i solved for t taking the initial velocity as zero. (b) i used...
  5. rocdoc

    About the first-order electric field correlation function.

    For a fixed point in space, the first-order electric field correlation function may be given as (Possibly incorrectly, see my "second" post to this thread)! $$\langle\vec E^*(t)\vec E(t+\tau)\rangle = {\frac {1} {T}} \int_T\vec E^*(t)\vec E(t+\tau)dt~~~~~(1)$$ Where T is a very large time and *...
  6. Const@ntine

    Chemistry Measuring the Mass & Electric Charge of Molecules

    Homework Statement Hi! So I stumbled upon this simple "plug n' play" exercise in my Physics textbook. Basically it gives you certain molecules/atoms, and tells you to measure the Electric Charge, and its Mass. Pretty simple, but I hit upon some hickups. Anyway, let's get to it: Find the...
  7. G

    Electric Potential Energy - Final Velocity

    Homework Statement Four protons (each with mass 1.7 10-27 kg and charge 1.6 10-19 C) are initially held at the corners of a square that is 7.1 10-9 m on a side. They are then released from rest. What is the speed of each proton when the protons are very far apart? (You may assume that the...
  8. K

    Electric field model using a cylindrical capacitor

    Homework Statement In a lab experiment we measured the potential at different points within a cylindrical capacitor electric field modeling plate thing (apparently that's the best I could do to translate that into English). The positive electrode was connected in the middle and the negative...
  9. S

    Small oscillations and a time dependent electric field

    Homework Statement [/B] Here's the problem from the homework. I've called the initial positions in order as 0, l, and 2l. Homework Equations The most important equation here would have to be |V - w2*M| = 0, where V is the matrix detailing the potential of the system and M as the "masses" of...
  10. P

    The electric field in an expanding, statically-charged tube

    Imagine that I have a straight, statically-charged, cylinder-shaped tube with arbitrary (ideally infinite) extent. The charge is distributed evenly over the tube such that the field inside the tube is zero. For convenience, let's line up the tube centered along the x-axis such that the...
  11. E

    How to find electric field given points of electric potentia

    I have what at first seems like a very simple problem, yet I have no clue how to solve it. There is 1 point defined to have 0V, and another point has exactly 1V. Assume there is nothing else in the universe. https://i.imgur.com/iv9oL5j.png How do I find the electric potential and field at any...
  12. P

    Induced Electric Field In Circuit With Varying Resistance

    Homework Statement This is irodov's problem #310 in electrodynamics A long solenoid of cross-sectional radius a has a thin insulated wire ring tightly put on its winding; one half of the ring has the resistance ## \beta ## times that of the other half. The magnetic induction produced by the...
  13. T

    Electric field outside 2 same charge parallel plates

    Homework Statement Given 2 positively charged parallel plates with equal surface charge densities, calculate the electric field at a point outside the the parallel plates. Homework Equations E= (surface charge density) / 2(relative permittivity) for a single sheet. The Attempt at a Solution...
  14. S

    I Are Electric and Gravitational Fields the Same for Moving and Stationary Objects?

    Hello! I was wondering if the electric and gravitational fields are the same for a moving and a stationary object. The electric field (assume it is created by a stationary charge) is ##E = \frac{q}{\epsilon_0 4 \pi r^2}##, for a stationary observer, but it is higher for a moving one, as the r is...
  15. T

    How does an electric motor convert electrical energy to mechanical energy?

    how does electric motor convert electrical energy to mechanical energy. Hello I do not understand the following electric power is P = V * I electric motors operate on the principle of repulsion and attraction of magnetism. What confuses me where that power ends because as far as I know, the...
  16. T

    Is it a magnetic or an electric field that causes induction

    Is it a magnetic or an electric field that causes induction in the antenna wiki says that: The electric field (E, green arrows) of the incoming wave pushes the electrons in the rods back and forth, charging the ends alternately positive (+) and negative (−). enter image description here...
  17. F

    Do Electric mosquito zappers work?

    Do Electric mosquito killers (which work by attracting mosquitoes by UV light) actually work? I have tried 3-4 different models. Two of them worked amazing on first day, but later they stopped attracting mosquitoes. Others never attracted mosquitoes. Is UV light supposed to attract mosquitoes ...
  18. D

    Electric Flux through Cubical Surface Enclosing Sphere

    Homework Statement A uniform charge density of 700 nC/m3 is distributed throughout a spherical volume of radius 6.00 cm. Consider a cubical Gaussian surface with its center at the center of the sphere. [reference picture] What is the electric flux through this cubical surface if its edge...
  19. 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...
  20. 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...
  21. Philosophaie

    I Electric Dipole Moments: Sun, Earth, Planets, Minor Planets, Moons

    Is there a table of Electric Dipole Moments, ##\bar p##, for the Sun, Earth, Planets, Minor Planets and Moons?
  22. 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...
  23. R

    Electric potential due to collection of charged particles

    Homework Statement A particle with charge q1 = -6.75x10^-6 is located at (0,3.25x10^-2 m ) and a second particle with charge 3.2x10^-6 is located at (0,-2.75x10^-2 m) what is the electric potential due to the two charges at the origin? Homework Equations V = kq/r The Attempt at a Solution So...
  24. N

    Using Gauss' Law to Calculate electric field near rod.

    Homework Statement No variables, just a conceptual question. Homework Equations Flux = EA = Q/ε The Attempt at a Solution Given a uniformly charged rod of FINITE length, could we use Gauss' law for electric flux to calculate the field at a point p a distance x away from the rod, so long as the...
  25. B

    Determine work done by electric field

    Homework Statement Given electric field ##\vec E = 6x^2\hat i +6y\hat j+4\hat z## v/m Find ## V_{MN}## if both M and N separate by M(2,6,-1) and N(-3,-3,2) Homework Equations The Attempt at a Solution here i find ##V_{MN}## by unit vector from N to M is ##\frac 1 {\sqrt (115)}(5\hat i +9\hat...
  26. V

    Battery sizing in an electric vehicle

    Hi.. i am working on a developemnt of electric vehicle as my final year project..i have calculated the max. power required by 800 kg vehicle is 30 kw.. so i am using 30 kw 3 phase AC induction motor.. now can you please help me out in sizing my battery pack.. weight : 800kg max. velocity : 80...
  27. Philosophaie

    Electric Field and Electric Dipole Moment for a Dipole

    The Magnetic Dipole Moment for a Magnetic Field for a dipole oriented on the x-y axis is: ##\bar m = |m| \hat z## The Magnetic Field is: ##\bar B = \frac{\mhu_0}{4 * \pi * |\bar r|^5} * 3 * \bar r * (\bar m . \bar r) - \bar m * |\bar r|^2## Vector Potential is: ##\bar A = \frac{\mhu_0}{4 * \pi...
  28. P

    Electric field above an off-center finite line charge

    Homework Statement There is a finite line charge with length L = 1 meter and linear charge density λ = 1*10^-16 C/m. Point P is h = 70cm above the line charge and distance x from the right end of the line charge. The magnitude and direction of the electric field at point P must be found. The...
  29. RJLiberator

    How Do You Calculate Electric Potential for a Given Charge Distribution?

    Homework Statement The volume charge density for some charge configuration is given as ## \rho (x,y,z) = \lambda \delta(x) \delta(z) [\theta(y+L)-\theta(y-L)]## where ## \theta(x)## is the step function, defined as ##\theta(x)=1## for x>0 and 0 for x<0. a) Calculate V(x,y,z), the potential...
  30. P

    Calculate strength of the electric field at indicated point

    Homework Statement https://imgur.com/a/wpir4 [/B] a. What is the strength of the electric field at the position indicated by the dot in the figure? Use the following values: q1 = 1.09 nC, q2=0.93 nC, d1=2.49 cm, d2=6.9 cm, d3 = 4.27 cm. b. What is the direction of the electric field at the...
  31. G

    What happens to the electric field's phase upon reflection?

    I have a problem with the phase of an electric field as it is reflected by and transmitted through a dielectric interface. At the boundary between the two media, all waves must exist simultaneously and the tangential component must be equal on both sides of the interface, right? Therefore for...
  32. T

    Electric field inside hollow conductor with a charge

    Ok, this might be a really dumb question, but I still am asking it: I was reading about gauss' Law when it comes to a hollow conductor with a (say) point charge inside it, and it seems intuitive to me that, in electrostatic equilibrium, the charges rearrange themselves to cancel the electric...
  33. Spinnor

    I Electric and Color charge in String Theory

    I get a gist of how electric charge comes about in string theory here, https://physics.stackexchange.com/questions/5665/electric-charge-in-string-theory How much needs to be amended to the above answer to understand how color charge comes about in string theory? I assume there are interesting...
  34. F

    Will this man get an electric shock

    If a properly insulated man touches with one hand +ve terminal of a 120 V battery and with another hand -ve terminal of (Edit: an another) 120V battery (two batteries are totally isolated, not connected in any way) then will he get electrical shock ? ( I am guessing , not). But if -ve terminals...
  35. T

    Electric field inside non-conducting spherical shell

    Homework Statement Figure 23-30 shows two nonconducting spherical shells fixed in place. Shell 1 has uniform surface charge density +6.0 µC/m2 on its outer surface and radius 3.0 cm. Shell 2 has uniform surface charge density -3.8 µC/m2 on its outer surface and radius 2.0 cm. The shell centers...
  36. Epoch

    Electricity: electric field in a point Between Two Charges

    Homework Statement I've seen many books writing the cosine rule like this: a^2 = b^2 + c^2 - 2bc cos A My electricity textbook for an electric field in a point between two charges says this: E resultant = root[E1^2 + E2^2 + 2*E1*E2*cos(angle between E1 and E2)] In the first equation it is -2...
  37. M

    Finding electric potential given two point charges

    Homework Statement Find the potential at points P1, P2, P3, and P4 in the diagram due to the two given charges. Homework Equations VP =k∑qi/ri p = q ⋅ d The Attempt at a Solution I'm not sure how to approach the problem. I thought about using that given equation four times and adding it all...
  38. M

    Strength of electric field given potential difference

    Homework Statement What is the strength of the electric field between two parallel conducting plates separated by 1.00 cm and having a potential difference (voltage) between them of 1.50×104 V? Homework Equations ΔV = qΔU ΔV = -∫E⋅dl E = kq/r2 The Attempt at a Solution I am not sure where to...
  39. I

    Electric power and internal resistance

    Homework Statement Today I did a laboratory work in which I had to find power and internal resistance. I used an ordinary battery so it's closed circuit. I did all tasks except writing a hypothesis and conclusion I can't really think of it. I don't know what to write since I just measure using...
  40. T

    Rotating a spherical conductor in an Electric field

    Hi, I recently came across the familiar image of a metal sphere in an electric field: https://i.stack.imgur.com/x58Ia.jpg I noted how the free-charges on the surface of the sphere align with the electric field lines as opposite charges are attracted. Then I wondered, 'what if the sphere was...
  41. Brendan Webb

    Electric Field of Equilateral Triangle

    Homework Statement Consider an equilateral triangle of side 15.6cm. A charge of +2.0μC is placed at one vertex and charges -4μC each are placed at the two. Determine the electric field at the centre of the triangle. Homework Equations E=kQ/r^2 The Attempt at a Solution I am hoping someone...
  42. R

    Electric Flux Equation for Rotating Loop?

    Homework Statement A circular loop with radius r is rotating with constant angular velocity w in a uniform electric field with magnitude E. The axis of rotation is perpendicular to the electric field direction and is along the diameter of the loop.Initially, the electric flux through the loop...
  43. G

    Limiting output voltage of an electric fence energiser

    My home-made energiser runs off a car battery and uses a 555 timer to pulse a Darlington-style pair of transistors. These pulse the primary of an ignition coil. Since an electric fence is an open circuit, I'm concerned about excessive voltages developing in the coil secondary causing...
  44. T

    Engineering Solving Circuit Diagram Homework - Test Prep Tips

    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...
  45. K

    Making an electric unicycle really self-balanced

    I recently came across electric unicycles, a cool and fun way fpr transportation. The wheel balances as a Segway by applying power to the wheel. (the classis reverse pendula). However, since its a unicycle, it does not balance sideways, and I imagine that this colud be solved with a...
  46. Iftekhar Uddin

    How an Electric Field is affected by an Insulator

    I looked through this forum post for an answer to my problem. It gave me enough insight to try and come to some conclusions but I'm still confused on some parts here and there about how I got my final answer. 1. Homework Statement A uniformly charged, straight filament 7.70 m in length has a...
  47. C

    Electric Field of Line Charge with Displaced Origin

    Homework Statement Positive charge Q is distributed uniformly along the x-axis from x = 0 to x = a. Determine a. The electric field produced by the charge distribution Q at points on the positive x-axis where x > a. b. A point charge q is then placed at x = a + r. Determine force on q due to Q...
  48. R

    Magnitude of electric field at point A using components

    Homework Statement https://imgur.com/gallery/YwCap In side are image of figure, and questions.Homework Equations E = kq/r^2 The Attempt at a Solution So I have an electric field where the y compontents cancel. I have 2Ecos(∂) = E (Electric field at point A) - 2 because there is a top and...
  49. L

    Can E=V/d be used to calculate the electric field of a dipole?

    This is from a lab where my team found the equipotential lines from the electric field of a dipole. The information I was given to calculate the magnitude of the electric field seems too simple, and for some reason I'm expecting this to be more complex. So, this is my attempt at double checking...
  50. A

    Breakdown voltage of humid air in uniform electric field

    Could anyone please let me know if breakthrough spark can happen, or, in general, what will happen in the below system? Note 1: the dielectric layers have a much higher breakthrough voltage than humid air. Note 2: the intensity of the electric field that develops in the flow of the humid air is...
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