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. W

    Do not try this at home kids......

    Found this interesting video - thought there would be interest here... VIDEO LINK
  2. M

    What Battery Bank Size Do I Need to Replace My 1250 kVA Diesel Generator?

    Hello, I have a bit of an issue and can't figure out how to find out the answer. I want to understand how to find out what battery I would need if I want to scrap the diesel generator I have and go for a battery bank. I have a 1250 kVA rated generator. PF is 0.85, Rated voltage is 400V, rated...
  3. RoboNerd

    Question about strength of magnetic field down coil (solenoid)

    Homework Statement Hi everyone. I was reading through a book and came across the following question and explanation: " You are given two 200 meter strands of identical copper wire. With one strand you create a coil whose radius is 2 cm. With the second strand you create a 4 cm coil. Assuming...
  4. I

    Generating High Voltage: Safe and Effective Methods for Amateur Use

    Good Afternoon everyone, Question: What are some effective ways to generate a high voltage (Multiple KV) using amateur equipment? I've dealt with high voltage before, so I'm aware of the safety issues. Anyway, here is what I've got thus far: If you go on ebay, and search for high voltage power...
  5. Tom1211

    How much electricity can be produced from 3000 rpm?

    If your axel in you car was magnetic with copper wire casing would that produce electricity? If so how much? If there is no resistance in that process then there wouldn't be a detrimental effect on the performance (bar added weight of the wire) With the raising popularity of electric cars it...
  6. H

    Static electricity and D Trump physics pic

    as far as I know this is real, from Scotland. could be a good discussion starter for static electricity;
  7. T

    Current of AC transmission lines and electricity in general

    Hi, I realized I didn't understand the physical model of something I know the theory of pretty well. I was considering the real power loss of an AC transmission line I2*R, then I realized that from source to load the electrons in an AC line don't actually move anywhere. (as far as I know) Yet if...
  8. Hons K Wyn

    Magnets and coils configuration for electricity generation

    My dad is working on a project where he intends to convert mechanical into electrical energy, and he was wondering if a particular magnet and coil configuration works for electricity generation. And if it does, how are the voltage and current calculated. Lets say: The coils have a diameter of...
  9. B

    Introducing Local Charge to Conductors?

    Homework Statement Is it possible to introduce local charge on a conductor? Homework Equations - The Attempt at a Solution I know that electrons can move freely from atom to atom in the conductor, so if you introduce excess electrons to the conductor, they'll spread out and there won't be a...
  10. Firye Stanly

    Electrical power of a lightbulb

    Homework Statement Two identical light bulbs are connected to the ends of the battery. In the first case they are connected in series and in the second they are connected in parallel mode. What is the ratio of the electrical power of light bulbs connected as mentioned? Homework Equations...
  11. Coldslooks

    Number of emitted photons per second

    Homework Statement The average wavelength that LED emits is 500nm. The electrical power of the LED is 300mW and the efficiency of turning energy into light is 66%. Number of emitted photons in unit time is? Homework Equations ##E_f=hcf## ##\frac{Pt}{E_f}=number of photons## The Attempt at a...
  12. A

    I Help with Experiment on Batteries

    Hi guys! I am currently having Physics Internal Assessment in my school and I want to do an experiment to calculate the different times it takes for a 9V cell to to discharge (reach a 0.1V) in different temperatures. The problem I am having right now is to efficiently discharge my cell. How can...
  13. K

    How Much Charge Passes Through the Lamp in 1 Minute?

    Homework Statement Ammeter shows 1.2 A and 1.0 A. How large amount of charge passing through the lamp in 1 minute? https://physicsforums-bernhardtmediall.netdna-ssl.com/data/attachments/84/84982-6e293679b3592fb475f0f9cac697526f.jpg Homework Equations Q=I*t[/B] The Attempt at a Solution I =...
  14. D

    Can Rain and Other Weather Effects Generate Electricity?

    can anybody tell me how to transfer tension energy into electricity, new project i am doing is to do with, if the force of rain can be transferred somehow using a tensioned material. (like a solar panel) and if so is it possible to actually create energy off of this and turn it into electricity...
  15. S

    What is the effect of efficiency on the cost of electricity?

    I'm having trouble understanding the effect of efficiency on the cost of electricity for a PV system. By the graph I've uploaded, as the efficiency of a PV system goes up, the cost of electricity goes up. But the equation in the other photo has efficiency in the denominator of the equation...
  16. J

    Effect of number of coils on current in a generator?

    Hello everyone and thank you for your replies in advance. I am currently doing a physics project where I am testing to see how the number of coils of wire effects the current generated when a magnet is run through the coil. I am currently just dropping the magnet through the coil from a constant...
  17. D

    The Movement of Electricity in a Space Ship

    Hello. I am an occasional poster here with little background but a big interest in the mental experiments (ME) of Einstein and others. Of particular interest to me are factors related to what I call the Classic Spaceship Mental Experiment. [mentor's note: a link to an unacceptable reference...
  18. AmishaPanchal

    How to convert movemnt/speed to electricity or other E.forms

    Hi I was wondering if there is a way to produce energy using the movement of vehicles on the road. I do not know which principles can come into picture, but I believe Electromagnetism/ detection is the way to go? If someone could at least throw me in the right direction of which field to...
  19. P

    Liénard–Wiechert potentials: Local or Material derivatives?

    If I took a charged particle and accelerated it, that acceleration would have an effect on charges potentials, allowing for the radiation of electromagnetic waves. This acceleration would be local to a point in spacetime and the observed potentials would depend on the frame of reference of the...
  20. I

    Static Electricity: Can You Still Get a Shock Off the Ground?

    A (possibly stupid) static electricity question: Person A is carrying an electrostatic charge. They touch person B, both get a shock. If both persons were off the ground(eg hanging from ropes) ...would they still get a shock?
  21. P

    Constant Charge/Current Densities with Accelerating Charges

    In classical physics, when electric charges accelerate, they are expected to radiate. Electromagnetic waves, are by their nature the result of changing electric and magnetic fields. But is it possible to have acceleration of charges without having changing electric and magnetic fields? One...
  22. S

    B Question about understanding conductors for EM course

    So in conductors, the electrons will distribute themselves to the surface via repulsion forces. But why do we say that the electric field inside is zero? If I put a positive charge inside, clearly it will move in some direction from the electric field of generated from the electrons. Also, are...
  23. R

    Process which electricity is generated (Nuclear power)

    Homework Statement I picked a nuclear power plant. I spent a bit of time researching what the basic process is and that's what I've arrived at so far. I'm not certain if the answer is complete/decent, it seems like a very complex process which even for 'point form' could be a page of...
  24. Nile Anderson

    Which Values Should I Use When Calculating Power in a Circuit?

    When I am calculating the power in the circuit , do I use the RMS values , or the peak values and why ?
  25. Kuzon

    Struggling with the rules behind electricity

    Homework Statement A moving particle encounters an external electric field that decreases its kinetic energy from 9480 eV to 8260 eV as the particle moves from position A to position B. The electric potential atA is -43.0 V, and that at B is +25.0 V. Determine the charge of the particle...
  26. S

    Step Up Transformer: Current AND Voltage Increased?

    Please help! I have recently completed an experiment on transformers, using a step up transformer. I am aware of all the theory that shows that in a step up transformer, the induced voltage should increase and the induced current should decrease. However, in my experiment, my hypothesis is not...
  27. S

    B Why does accelerating a loop through a constant magnetic field induce an EMF?

    So from Faraday's law, a change in the magnetic flux will induce an emf on a loop of wire. { \phi }_{ B }\quad =\quad BA\\ { \varepsilon }_{ ind }\quad =\quad \frac { d{ \phi }_{ B } }{ dt } (in this case a perpendicular field) From these equations, it looks like the only way to induce a...
  28. S

    How Does an Inductor Affect Current Change Upon Switch Closure?

    Homework Statement In the following figure, R1= 3.1 Ω, R2= 4.9 Ω, L1= 0.155 H, L2= 0.2 H and the ideal battery has ε = 5.6 V. Just after switch S is closed, at what rate is the current in inductor 1 changing? Homework Equations { \varepsilon }_{ induced }\quad =\quad L\frac { di }{ dt } \\...
  29. S

    Magnetic field outside of a solenoid conceptual

    How come the magnetic field outside a solenoid is practically zero? I've read reasons along the lines of: -The magnetic field cancels out on the outside. Of course the net force cancels out, but what if you have an object placed on just one spot? The force on that object clearly is not 0...
  30. RoboNerd

    Classical Good self study book for Electricity and Magnetism

    Hi people! I am a high school rising senior who is looking to self study electricity and magnetism over the summer. Particularly, my aim is to take the ap physics c electricity and magnetism exam as a result of this self study but also to realize if I want to work with hardware/electrical...
  31. A

    Where does the magnetic field go for the electron?

    Homework Statement **Question** Is the magnetic field directed into the page or out of the page?Homework Equations Right Hand Rule The Attempt at a Solution My index finger is pointing downwards, and since the magnetic force is towards the right and this is an electron (negative) my thumb...
  32. A

    Magnetism, electricity, and photons

    If photons are part of a magnetic field like electrons, which electrons can be read with an amp meter, what can measure or count photons? Electrons are not counted but the magnetic field changes when more current flows and the ammeter reads a change in the magnetic field. What type of light are...
  33. S

    How Does Biot-Savart Law Calculate Magnetic Field at Point P?

    Homework Statement The figure shows two very long straight wires (in cross section) that each carry a current of 3.19 A directly out of the page. Distance d1 = 6.00 m and distance d2 = 4.00 m. What is the magnitude of the net magnetic field at point P, which lies on a perpendicular bisector to...
  34. V

    Unable to understand how higher current results in lower p.d

    To start with this is not a numerical but merely a basic concept I fail to understand. I will quote what the CIE book says "Consider a battery of emf 3 V and of internal resistacne 1 ohm. The maximum current that can be drawn from this battery is I=e/r = 3/1=3 A The terminal p.d of the battery...
  35. N

    Understanding the Relationship Between Resistance and Brightness in Lightbulbs

    The light in a lightbulb is the result of an increase in temperature. This increase is created by both a highter elektrical resistance in the wire and a highter elektric current. But a higher resistance results in a lower elektric current (I) (I=V/R), so it is both increasing and decreasing the...
  36. P

    Finding an electric field at a point from a line of charge

    Homework Statement A thin insulating rod with charge density lambda=+5nC/m is arranged inside a thin conducting cylindrical shell of radius r =3 cm. The rod and the shell are on the same axis, and infinite in length. What is electric field at point p? 6cm from the central axis. Homework...
  37. alexandria

    Calculating the cost of electricity

    Homework Statement Homework Equations Cost = rate x energy consumption (kWh) Energy consumption = power (kW) x total time (hrs) The Attempt at a Solution so here are my answers, can someone please verify if these are correct, thanks! a) To calculate power: There are fifteen 100 W...
  38. S

    About electricity and the EMF -- Multiple choice question

    Homework Statement The cell in the circuit has an emf of 2.0 V. When the variable resistor has a resistance of 4.0 Ω, the potential difference (pd) across the terminals of the cell is 1.0 V. What is the pd across the terminals of the cell when the resistance of the variable resistor is 12...
  39. G

    Electricity: plastic on plastic

    We know that objects like plastic become negative (with rubbing) but what will happen if we rub plastic and plastic, one of them will become positive which one ?
  40. Jeffb47

    Converting torque to electricity

    We have a solar tracking device that uses phase change of paraffin wax when heated inside a solar receiver. With a helical slot in a torque tube we can translate the expansion into rotational motion. We use this rotation to point solar panels at the sun, thus generating more electricity. Look...
  41. Biker

    Static Electricity: Why We Get Shocks on Carpet & Door Knobs

    Here is the rub. Most of the online sources and in a kind of statement in my book says that we gain a negative charge when we rub our feet on the carpet. So when we touch a door knob we get a electric shock because the electrons is transferred from us to the door knob However, Shouldn't it be...
  42. Titan97

    Heat generated due to motion of wire in magnetic field

    Homework Statement A wire is moved with constant velocity such that the motion is perpendicular to the length of the wire in a region containing magnetic field perpendicular to the plane of motion. The wire has a resistance R. Will thermel energy be generated in the wire? Homework Equations...
  43. S

    Resistance: Definition & Difference Explained

    My professor says resistance depends on, R\quad =\quad \frac { \rho L }{ A } And is defined as, R\quad =\quad \frac { V }{ I } What does she mean? What is the difference? A definition is denoted by \equiv, what is the difference between that and an ordinary equal sign?
  44. S

    Magnitude of the E-Field at the center of curvature

    Homework Statement A circular rod has a radius of curvature R = 8.11 cm, and a uniformly distributed positive charge Q = 6.25 pC and subtends an angle theta = 2.40 rad. What is the magnitude of the electric field that Q produces at the center of curvature? Homework Equations E = kQ/r^2 6.25 pC...
  45. S

    Finding velocity given potentials of two parallel plates

    Homework Statement A charged particle (either an electron or a proton) is moving rightward between two parallel charged plates separated by distance d=2.87mm. The plate potentials are V1=-75.8V and V2=-49V. The particle is slowing from an initial speed of 90.0 km/s at the left plate. What is...
  46. V

    What Happens to Unused Electricity in Distribution Transformers?

    I Have a Dumb Question. If Electricity Supplied from Substation to Feeder to Transformer and Under Transformer If There Are Many Consumers. Assuming That many Consumers Went on for a Holiday, Does Utility Still Pay for the Electricity to the Generation company for the Electricity they Supplied...
  47. S

    Electric field lines from a metal shell and sphere

    Homework Statement A metal sphere of charge +6μC is surrounded by a metal shell of net charge +6μC. Which of the following diagrams represents the electric field lines of the system? Homework EquationsThe Attempt at a Solution The correct answer provided by my teacher is a figure with 12...
  48. shintashi

    Confusing terms? Live, Common, Neutral, Ground....

    OK, so I've gone through probably 90 tutorials on electricity and related topics, and there's a bundle of terms I ran into, used by people ages 12-80 with a dozen different accents and twice as many time zones. (So I'm not sure how many terms are universal and how many are provincial). Live...
  49. T

    Question of electricity net force

    Homework Statement Three point charges are located on the positive x-axis of a coordinate system. Charge q1 = 1.0 nC is 2.0 cm from the origin, charge q2 = -3.5 nC is 4.0 cm from the origin and charge q3 = 6.0 nC located at the origin. What is the net force ((a)magnitude and (b) direction) on...
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