Electricity Definition and 999 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. S

    Shielding Dirty Electricity Ground Current

    Would using an insulator like rubber tires partly buried in the ground + partly protruding above the land surface to create a continuous perimeter around a piece of land possibly shield the land inside of it from the accumulation of charge on the surface of the Earth which occurs in the vicinity...
  2. Viona

    B The resistance of an ohmic conductor

    I know that the resistance of an ohmic conductor increases with length because the electrons going through the conductor must undergo more collisions in a longer conductor. But why decreasing the cross-sectional area of the conductor also increases the resistance of a conductor?
  3. Istiak

    The Electric Field and Potential Energy in a Spring System

    Solution attempt
  4. P

    Why Can't Current Flow Between Two Same Voltage Nodes?

    The question is to find the resistance between points A and F. I understand that the resistor between OC can be removed. From this point onwards, resistor OC has been removed. Let the far right point of the diagram, where i5 and i7 exit from, be B. Is it possible to detach the remaining...
  5. S

    Convection current in electricity

    So, I randomly came upon this in a textbook that I was skimming and I think I have a very very surface ideea of what it's about but I want to read and know more in order to understand the fenomenon in much more detail. Any help in any form would be much appreciated! P.S.: This is my first post...
  6. amizy9990

    2 * 10 ^ 20 charges move in a wire when we connect a 3.7 V battery. Ho

    W=Q*V 2*10^20 Q * 3,7 V= 7,4*10^20 ??
  7. amizy9990

    A copper wire contains 3.0 *10 ^ 22 number of charges on 1 meter wire

    A copper wire contains 3.0 *10 ^ 22 number of charges on 1 meter wire. What speed do the electrons move when there is 2 A current in the wire. t=q/t=3,20*10^3 C/ 2.0 A = 1,5*10^22 s v= 1m/1,5*10^3s= 6,6*10^-4 m/s
  8. P

    Stewart-Tolman Effect (Current caused by Acceleration of wires)

    Consider the inertial reference frame in which the positive ions forming the crystal lattice of some portion of a metallic ring are at rest. In this frame, an inertial force of mra exists. Consider the electrons in this portion of the metallic ring. The inertial force of mra is exerted on the...
  9. P

    Do charges always lie on the inner surface of capacitors?

    Parallel plates A, B are 5mm apart, with charges +1C and -1C respectively. Parallel plates C, D are 2mm apart, with charges +1C and -1C respectively. Capacitor CD is slid between capacitor AB. Find the potential difference between AB. The key idea to solving this problem is to suppose that +1C...
  10. P

    Difficult capacitance problem -- 3 long concentric metal cylinders

    A solution I found online claims that the effective capacitance between the middle and inner shell can be seen as: C (effective) = C1 + C2, where C1 is the capacitance between the inner and outermost shell, and C2 is the capacitance between the middle and outermost shell. Apparently C1 and C2...
  11. P

    Electrical energy stored by charged concentric spherical shells

    I thought up of this problem myself, so I do not have solutions. I would appreciate if you could correct my approach to solving this problem. Firstly, the charge induced on the inner surface of shell B is -q, and so the charge on the outer surface of shell B is Q+q. The energy stored can be...
  12. P

    Principle of superposition for charges/induced charges

    The key observation to solve the above problem is that the charge Q can be dragged out into a flat capacitor plate parallel to the 2 existing plates. Apparently, while the charge distribution on the 2 existing plates changes, the total charge induced on each plate remains the same, due to the...
  13. P

    Force needed to hold together a capacitor

    I have 2 methods, which give 2 different solutions: Let sigma = charge per unit area Let plate 1 be the left plate, plate 2 = right plate. Method 1: Because they are insulating, consider the electric field at 3 regions; region 1 to the left of plate 1, region 2 between the plates, and region 3...
  14. P

    Why is the pressure on a charged sphere only exerted on the contact area?

    The force per unit area (Pressure) on a part of the sphere is given by F = (E outside + E inside)/2 * Q = 0.5 (kQ/R^2) * (Q/ 4piR^2) = (Q^2/ 32pi^2 e0 R^4). I understand the above line. The solution then says this pressure is exerted on the contact area between the 2 spheres, as given by...
  15. T

    What materials produce higher levels of static electricity?

    A lot of people know the example of a carpet and a doorknob. You accidentally rub your foot to the carpet and then get a static shock after touching the doorknob. Why does carpet produce higher static electricity than for example hardwood or something. Is it because of the hairs? Is it because...
  16. Doma Noemi

    Electricity in the human body -- Is there enough to power a prosthesis?

    Can we use the electricity from the muscle to power an engine (like a prosthesis)?
  17. astrodummy

    Does electricity have a propagation delay?

    Suppose you have a battery wired to a light bulb and switch via a long pair of conductors, say 1 light second long. Assume for now that electricity travels at c. The switch is thrown. How long does it take the bulb to light? Does the electricity take 1 second to get from the battery to the...
  18. L

    Can Electricity Generators Survive with LCOE Higher than Wholesale Prices?

    I can't see how electricity generators can make money. I am from Australia so multiply figures by around 0.7 to convert to USD. Electricity prices and power generation have become a bit of an ideological battle ground in my country so prices are in the news . Whole sale electricity prices seem...
  19. Byron Forbes

    How Fast Does an Electrical Impulse Travel in a Copper Wire?

    The topic here is about the speed that the "electrical" signal (impulse) travels at in a copper wire. The speed is well known to be just under c. Often when this topic is spoken about, the term "EM field" is used and I don't understand why. We have electrons with a power supply that supplies...
  20. E

    Could you check this Li-ion charging circuit?

    Can secondary cell can be described in circuit simulator?? With other symbols like capacitor. Also I wonder if there's a program that provide secondary cell(like Li-ion battery). Please help me
  21. F

    Trying to better understand the physics of electrical earth ground

    I'm trying to better understand the physics of how Earth ground works. In circuit analysis and other electronic courses they usually present a conceptual picture like below where the Earth is viewed as a path that completes a circuit? In this conceptual view, the current travels on the...
  22. Kaushik

    Does potential drop when a charge flows through a wire w/ 0 resistance?

    Let us connect a battery of potential difference V to a wire. There is no resistance. Nothing! Now the battery creates some potential difference and the charges in the conducting wire move due to the Electric field created in the conductor by the battery. So, as the charge moves, its potential...
  23. H

    History Why didn't ancient civilizations harness the power of electricity?

    I think the greek knew about magnets and magnetic stones. They also knew about statistic electricity the Egyptian knew about a fish which would shock you . My question is why did it take so long for someone to wrap a magnet around a coil. What is the earliest in human history that humans could...
  24. Kaushik

    Intuition about electromotive force (EMF)

    My understanding of emf Let us consider 2 parallel plates with charges (opp. but equal in magnitude) stored on it. When we connect both the plates from the outer side, the electrons from the lower potential (i.e., negatively charged plate) moves to the higher potential (positively charged plate)...
  25. Nomadyb

    Find EMF of ℰ on Wire: Speed v, Force, C, B, m, g, l & a

    a) the EMF of ℰ induced on The Wire, as a function of the speed 𝑣of the wire you can find it. b) flow induced in the wire𝑖, 𝐶, 𝐵, and are denominated in 𝑙 𝑎 (𝑎= the acceleration of the wire). c) find the magnetic force acting on the wire in𝐶,𝐵, 𝑙 and𝑎. d) 𝑎 acceleration, 𝑚, 𝑔, 𝑙, and are...
  26. DerbisEternal

    How do I proceed with two different trig functions containing x on the left?

    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?
  27. The-dude

    Static Electricity- Solving Material Placement Issues

    Hello, I'm trying to solve a material placement issue at work and I'm exploring the idea of using static electricity to solve it. We currently combine two materials together using a heat activated glue that's sandwiched between the two materials and pressed together using a heat press...
  28. M

    How to calculate the efficiency of a switch mode power supply?

    I know how to calculate the power output and input by analyzing the current in put and output with multimeters and using the formula P=VI. But P_out is obviously incomparably smaller than P_in so the efficiency would suck this way. Is there a better way to do this??
  29. Kaushik

    Understanding EMF and Potential Difference in Electrical Circuits

    Is emf the work done to move a positive charge from LOWER potential to HIGHER potential to maintain the potential difference or else the charges move from higher potential to lower potential and will reach a point where the potential is the same between the two points and the charge will stop...
  30. Russ Edmonds

    Fishing for atmospheric electricity

    Fishing for atmospheric electricity.Three microcuries of Am-241 were placed in a aluminum pie tin. The pie tin was then suspended 2.7 meters in the air by a fishing pole. The pie tin was insulated from ground by the nylon fishing line. A wire connection was hung from the pie tin to the top...
  31. D

    Physics Homework about using Electricity to Heat Flowing Water

    This is the question: You want to make an electric instantaneous water heater in which 5.0 liters of water flows past a resistance per minute and heats water from 10.0 ° C to 45.0 ° C. Calculate the magnitude of the resistance to use and the amperage. The flow-through is connected to 230V So...
  32. Leo Liu

    Understanding the Electric Field of a Charged Sphere

    This page claims that "[t]he electric field outside the sphere is given by: ##{E} = {{kQ} \over {r^2}}##, just like a point charge". I would like to know the reason we should treat the sphere as a point charge, even if the charges are uniformly distributed throughout the surface of the...
  33. M

    Electricity Problem: Solutions and Causes

  34. Sokolov

    Maximum voltage that can be applied to DC circuit with resistors

    I see that ##V_{ac}=V_{ab}+V_{bc}##, with ##V_{ab}=I_1R_1=I_2R_2## and ##V_{bc}=I_3R_3##. However, I don't see how to express mathematically the maximum value of ##V_{ac}##. Could someone please help me with this task?
  35. E

    Nuclear Power Plants - Electricity Production

    I've calculated that reaction-energy in fission of a single atom of Uranium-235 is 2.5977713481*10^-11 Joules (based off of the equation given above.) I'm assuming that PWh has to be converted into simpler units so, 2.49PWh = 2.49*10^15Wh.. afterwards I could make it into watts but I was never...
  36. danielhaish

    Which surfaces get positively charge by grabbing (static electricity)

    So is it becouse the material or becouse the fact that the balloon is the object that moves and the hair is static. and does every two objects that been grabed together will nacessrly continues each other. and also why does the minos of a bttary doesn't stick to the flower
  37. M

    Inducing electric current in a wire (a comparison)

    Consider the following experiment: from a lacquered copper wire we cut off twenty to thirty pieces of about 10 cm. From them we form a bundle of parallel wires and connect the two ends with one more wire each. The other ends of these two wires are connected to a sensitive analog ammeter. We hold...
  38. D

    Turbogenerator electricity output and combustible quantity

    Hello, Is there a formal mathematical link between the amount of electricity that a turbogenerator produces and the corresponding combustible quantity? I understand that, in the case of a gas turbine, rotation and therefore mechanical energy is converted to electrical energy (preceded by a...
  39. DaveC426913

    Why are my living room lights and outlets not working after resetting breakers?

    A year or so ago, I had a licensed electrician come in and retroactively fix up some of my wiring (My amateur fingers did nothing near the panel, just extensions to existing lights and outlets). He ran new cable and installed a couple of new breakers for them. My basement has been gutted to...
  40. ConradG

    Why do powerplants sell electricity for a negative price?

    Hi all, sorry in advance if this is a dumb question, I am not an electrical engineer but find the topic fascinating! My question is: Occasionally powerplants sell electricity for a negative price due to excess supply, such as in Germany...
  41. C

    Does Polarity and Current Direction Affect Energy Flow in AC Circuits?

    I assume that because there is a resistance, the polarity of the voltage must be the same as the charge flow, and thus the current, in order for energy to flow in the same direction. For instance, could I use the example of a light bulb (the resistor) plugged into AC lines; we know that if the...
  42. T

    District heating vs. electricity generation

    My city has large district heating system, where the heat is generated at an incineration plant. I'm personally not a fan of district heating, and I would rather see the plant generate electricity through steam instead. I don't know if that was ever considered when the plant was built. Are there...
  43. menniandscience

    Retarded and advanced potentials

    "of the two types of solutions which the Maxwell equations yield for the wave equation, the retarded and advanced potentials, only the retarded field seems to have a physical meaning," let's start please with basic (and detailed as possible for the knowledgeable layman! p.s-which equation is...
  44. A

    Confused about Polarization and Induction - Static Electricity

    Hello. Recently we began taking static electricity and our teacher asked us to do a research paper on static electricity and charges in general to help us understand the material better. I've been stuck a bit on trying to understand what's the difference between polarization and induction and...
  45. hiddenname

    I Electricity & Planetary Magnetic Field Reversal: Implications & Studies

    What is/are the potential or theoretical effect on electricity due to reversal of planetary magnetic field? Would circuitry continue to function or would knowledge and understanding need re-evaluating as a result of a reversal of our magnetic field on planet Earth? Note: this is not a homework...
  46. O

    I Efficiency of computers vs. brains

    Hi, I’m an undergraduate student interested in cognitive processes. I’m about to ask a very interdisciplinary question, and so hopefully I can find a physicists that can take on the challenge. What is the fundamental reason behind why modern electronic computers (transistor computers) are...
  47. I

    Inserting a dielectric material between two plates of a capacitor

    1. new capacity: ##C = K\cdot C_{0}##. 2. initial potential energy: ##U_{i} = \frac 1 2 \cdot C_{0}V_{0}^2##. 3. final potential energy: ##U_{f} = \frac 1 2 \cdot KC_{0}V_{0}^2##. 4. total work done: ##W_{tot} =\Delta U = U_{f} - U_{i} = \frac 1 2 \cdot (K-1)C_{0}V_{0}^2 > 0##. 5. also total...
  48. D

    Joule heating effect - qualitative explanation

    Hi, I understand mathematically why using low resistance results in a greater heating effect. Could someone give an intuitive and microscopic picture of why the current contributes more to a greater power dissipation by the resistor rather than the resistance contribution to the power...
  49. R

    Can I store electricity from a wind turbine directly into a battery?

    Hello, This is an enquiry about the wind turbine electricity and battery storage. I am framing it based on my limited understanding. Please advise me. I intend to install and capture the wind energy through a small wind turbine at my home. The turbine shaft will be directly connected to the...
  50. Guidestone

    Request for historical background on the concept of voltage

    Hi all. I'll get to the point. I've been interested in electricity since I was in college. Concepts such as current and resistance seemed easy to grasp for me but voltage remains a little bit obscure. It's thanks to this forum (specially forum members Jim Hardy r.i.p and SophieCentaur, sorry if...
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