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. T

    Making a fomula to calculate the max power (electricity)

    Homework Statement Show how you can make a mathematic formula for maximum power, by using the other formulas. I think, that U is maybe called V in English. Homework Equations U= R*I Up = -ri *I+U0The Attempt at a Solution [/B] P=I·(-ri·I+U0)P= -ri·I2+U0 I
  2. L

    Overall Electric flux of a rigid body

    When we looked at some closed surface, we defined the overall electric flux of that surface as the sum of all infinitesimal fluxes of all the infinitesimal surfaces that make the quoted closed surface. Does that change if we do not have a closed surface, but a rigid body such as, let's say, a...
  3. Elvis 123456789

    Magnetic Field at the center of a square loop

    Homework Statement A square wire loop 12.0 cm on each side carries a clockwise current of 15.0 A Find the magnitude of the magnetic field at its center due to the four 1.30 −mm wire segments at the midpoint of each side. Homework Equations B = (μ0*I)/(4π)*(2a)/(x√(x^2+a^2)) The Attempt at a...
  4. Elvis 123456789

    Magnetic Field at center of a Square loop

    Homework Statement A square wire loop 12.0 cm on each side carries a clockwise current of 15.0 A Find the magnitude of the magnetic field at its center due to the four 1.30 −mm wire segments at the midpoint of each side. Homework Equations B = (μ0*I)/(4π)*(2a)/(x√(x^2+a^2)) The Attempt at a...
  5. K

    How to conduct electricity through water without electrodes?

    More specifically, how to conduct electricity through water without submerging electrodes into water? I can't think of other way except using high voltage to arc across air into water, but this method only work for high voltage. Any ideas? Thanks
  6. G

    Why not transmit electricity in 4-phase?

    Or even better, generate in 4-Phase, convert to two-phase for transmission. Even number phases cancel out nicely (contrary to popular belief, 3-phase does not actually cancel out). 2-phase might be convertible back to four phase for the purpose of industrial motors. Forgive me for speaking out...
  7. gsmtiger18

    Calculating Electric and Magnetic Field amplitude

    Homework Statement A circular uniform laser beam has a power of P = 3.2 mW and a diameter of d = 8.5 mm. The beam is a form of electromagnetic raditation with both electric and magnetic field components. (a) Calculate the intensity of the beam in units of W/m^2 (b) Calculate the energy (delta...
  8. Elvis 123456789

    Distance between Isotopes in a mass spec

    Homework Statement Suppose the electric field between the plates P and P' in the mass spectrometer in following figure is 1.89×104V/m and the magnetic field in both regions is 0.668 T. If the source contains the three isotopes of krypton, 82Kr,84Kr, and 86Kr, and the ions are singly charged...
  9. F

    Method of images about a sphere with a dipole

    Homework Statement Hello everyone, I am new here and have a question regarding method of images in my electricity and magnetism class. I need help to even get the ball rolling. The question is as follows: a) What is the image of a dipole, oriented toward the center of the conducting sphere, if...
  10. CollinsArg

    Other Where can I get the work "De Mundo" by William Gilbert?

    it's an old book of science, where can I find all those old science work to study science through its history?
  11. Elvis 123456789

    Projectile Motion in an Electric field

    Homework Statement Protons are projected with an initial speed of v0 = 10^5 m/s into a region in which a uniform electric field E = 800N/C [down] is present. The protons are to hit a target that lies a horizontal distance of 10.0 mm from the point at which the protons are launched. a) find the...
  12. PhyBoy

    Solving Hall Voltage Problem Homework Statement

    Homework Statement [See the figure attached] a) Find the relation between velocity of electron v and current I. b) Because of the magnetic force on the electron they move at the edge of conductor as shown in the figure and create a electrostatic force that oppomagnetostatic force. Find the...
  13. M

    The Electric Potential Equation

    Homework Statement An object with charge q = −4.00×10−9 C is placed in a region of uniform electric field and is released from rest at point A. After the charge has moved to point B, 0.500 m to the right, it has kinetic energy 5.00×10−7 J .What is the magnitude of the electric field? Homework...
  14. A

    How Does Current Flow in an Equipotential Conductor?

    i have studied that a conductor is equipotential and charges don't flow through it but how does it flow through a wire?
  15. M

    Can this electric motor generate electricity?

    http://imgur.com/6iPdcyJ http://imgur.com/6iPdcyJ This question may sound stupid, but I'm curious. Can the electric motor generate electricity if you spin the axle rod? Do the positives and negatives gain charges? EDIT: Image may not work, http://imgur.com/6iPdcyJ
  16. Elvis 123456789

    Classical Recommendation for rigorous intro books to mechanics and E&M

    Hey guys I'm a sophomore in college currently taking physics 2(intro E&M), Multivariable calculus, and Differential Equations. I was hoping some of you guys could recommend some good books for intro mechanics and E&M. I'm currently using University Physics by Young in my E&M class, and I used...
  17. UchihaClan13

    What is the explanation for the electrostatic force between two charged bodies?

    Okay guys It's no wonder I love electrostatics I keep on getting so many doubts Okay my doubt goes like this Consider 2 charges(q1and q2 having masses m1and m2 (here i am assuming that these two aren't point charges and therefore don't have negligible volume/mass) Okay so i am neglecting the...
  18. M

    How do I compute electric flux through a half-cylinder

    Homework Statement In figure 1, take the half-cylinder's radius and length to be 3.4cm and 15cm respectively. If the electric field has magnitude 5.9 kN/C, find the flux through the half-cylinder. Hint: You don't need to do an integral! Why not? Homework EquationsThe Attempt at a Solution I...
  19. S

    Are a substance's electrical and heat conductivity related?

    For example can an object be very conductive to electricity but be a very poor conductor of heat and vise-versa, or is a good conductor of one always a good conductor of the other and a bad conductor of one always a bad conductor of both? If they are related, then how and why are they connected...
  20. M

    What can I make to keep track of time without electricity

    I need to make a time keeping apparatus that doesn't require electricity. It needs to be something I can make at home and can obtain the resources from a local department store(menards or Home Depot etc.). Any suggestions?
  21. abrogard

    Are Electrons in Different Energy States Responsible for Variations in Power Output?

    Simple level question this: How many kinds of electrons are there? Like if 1 Amp = 6.24 x 10^18 electrons and Watts = Amps x Volts then in our local 240V system the watts = 240. = 0.24 kW. Now if we take that 1 Amp in an American 120Volt system then the Watts = 120W. So the same stream...
  22. Elvis 123456789

    Calculating Electric Field Using Gauss' Law for a Charged Insulating Slab

    Homework Statement A slab of insulating material has thickness 2d and is oriented so that its faces are parallel to the yz-plane and given by the planes x=d and x=−d. The y- and z-dimensions of the slab are very large compared to d and may be treated as essentially infinite. Let the charge...
  23. AstroJMT42

    Switches changing brightness of bulbs

    Homework Statement All bulbs are identical, (no information given on resistance so assuming all the same) All the switches are closed and then S1 is opened, Does bulb 6 get brighter, dimmer or stay the same? Does bulb 4 get brighter, dimmer or stay the same? Explain briefly why. Homework...
  24. V

    Doubt on equipotential surfaces

    i know that all conductors are equipotential,then how are charges flowing in a conductor?and at times in we say that charges won't flow since two points are equipotential(like in wheat stone bridge we say that charge won't flow across the capacitor/resistor since the ends of the 5th...
  25. R

    (Simple Electromagnetics) A charge placed between 2 charges

    Homework Statement A charge (q) is placed in-between two other equal charges named Q. Q-----q-----Q a) If both Q's are positive, is charge q in equilibrium? If yes, is it a stable or unstable equilibrium? b) What about if one Q is negative while the other is...
  26. N

    Magnetic field and electrical fields

    Can someone please explain to me why, a changing magnetic field can produce an electric field and a changing electrical field can produce a magnetic field. Also how do magnetic fields originate, what causes them?
  27. **Mariam**

    2 capacitors reaching equillibrium?

    Homework Statement A capacitor 1 of 3nF is charged with 3 volts. When it is completely charged, we connect it to an uncharged capacitor 2 of 7 nF. Calculate the charge on each capacitor after they reach electric equillibrium. Homework Equations Q=CV The Attempt at a Solution my confusion is...
  28. N

    Electrical Fields within the body

    So I was thinking, if the body has its own electrical currents... especially in the brain, then the brain must have an electrical field that extends infinitely. If that is the case can the brains electrical field interact with the real world and influence it. So for example if the field was...
  29. S

    Nuclear fusion power plants - why is it taking so long to make them?

    Hello everyone and happy new year! I would like to ask why it takes so long to create nuclear fusion power plants. The world's first nuclear fission power plant to generate electricity was started in 1954, some nine years after the nuclear fission bomb was detonated. Now we are more than 50...
  30. A

    AC frequency and power of an electrical appliance

    So the frequency in the power grid is 50 - 60 Hz depending on country's electrical standard. If I have a ~2000 watt heater that runs on 220 volts ~ 9 amps at 50 Hz, would increasing or decreasing the frequency effect the power output of the device. For example if I make the device run at 75 Hz...
  31. MidgetDwarf

    Intro Physics How does KIP Fundamentals of Electricity compare to Purcell?

    How does KIP: Fundamentals of Electricity and Magnetism compare against Purcell? Are they at the same level? Or would focusing on Purcell be a better option? I took an honors EM class and are assigned text was Purcell. It was the first time our school used Purcell for an honors sequence...
  32. Vinay080

    Other Experimental Researches in Electricity: Series One

    I have already got Faraday's "Experimental Researches in Electricity: Volume 1", which consists of 14 series of experiments concentrated in only one book. But, I wanted to see the more concentrated books, i.e the books of each series, to understand the situation then in elementary way. And even...
  33. K

    Honeycomb structure of oil due to an electric field

    Hi, I've been working on a problem for some time now and I can't figure out why exactly this happens, and I've been looking for some insight. The phenomenon can be seen in this video. We can see that the oil rearranges itself due to a high-voltage electric field. Thinking about this, my...
  34. E

    Acetone in water influence its enthelpy of vaporization

    Hi Everyone, I'm currently developing a waste heat recovery device as a side project. The system I've created uses a solution of acetone and water. One step in the process involves vaporizing acetone from the water at a low grade heat temperature (note: acetone does not form an azeotrope with...
  35. Dlhill13

    What are some liquids that can give up valence electrons when heated?

    Hello everyone, I am currently working on a project to design a more efficient method of electricity production in the nuclear industry. I haven't been able to find anything online (and chemistry isn't exactly my strong suit most of the time), but I wanted to know if anyone knows of a liquid or...
  36. B

    Chemistry "Simple molecular structure do not conduct electricity" H2O?

    Homework Statement Book says "Substances with a simple molecular structure do not conduct electricity. This is because they do not have any free electrons or an overall electric charge". Homework EquationsThe Attempt at a Solution I think the statement is a generalization because water is a...
  37. A

    Intro Physics Electricity and Gravity Question

    Two pith balls, each with a mass of 5.00g, are attached to non-conducting threads and suspended from the same point on the ceiling. Each thread has a length of 1.00m. The balls are then given an identical charge, which causes them to separate. At the point that the electrical and gravitational...
  38. D

    Question about Purcell - Electricity and Magnetism

    In chapter 5 of Purcell's Electricity and Magnetism, he shows using principles of special relatives that the magnetic force of a current carrying wire on a moving charge is equivalent to the charge experiencing an electric force in its own frame of reference. His argument is that when the...
  39. A

    Can Moving a Magnet Near Copper Wire Generate Usable Electricity?

    Hey guys :) new here, Just a simple question to get started. looks like a great forum :D Is the following statement correct or incorrect? If I hold a normal magnet with north and south poles, and I move my hand in one direction parallel to copper wiring, will it generate...
  40. V

    Magnet moving over surface creating levitation

    Hi, I've been doing reading on Halbach Arrays moving over surfaces and generating repulsive forces. From my understanding, the moving magnet induces a circular electric current in the metal track, which gives rise to a magnetic field. However, I'm having trouble understanding why this field...
  41. M

    Why is Plasma a good conductor of electricity?

    What gives it this property?
  42. L

    Fuel efficiency, turbine vs stroke generator

    Hi, I'm trying to figure which is more fuel efficient, turbine vs stroke generators. This honda stroke engine generator does 1000w for 3.8 hrs with 0.6 gallons of fuel or 2.3 liters, so the power per liter of fuel is 1,300 kW. http://powerequipment.honda.com/generators/models/eu1000i Then I...
  43. Shashank Verma

    Understanding Electricity and Magnetism: Solving Practice Problems

    The 4 questions have been uploaded as 2 jpeg files. I need step by step proper solutions as a pdf or word file if possible. Please help. Send the solutions to my email id : pyplx7x@gmail.com
  44. choopie

    A fun thought experiment: the science of electric superpowers

    Context: I'm an artist working with a writer on a superhero comic. One of the characters we were thinking of adding is a person with electricity powers. However, the writer wants the electricity powers to be somewhat more "realistic" (at least, aside from the whole electric super-powered human...
  45. Ronie Bayron

    Nuclear Direct Electricity Conversion

    Why are nuclear plants operate in a secondary steam engine for electrical conversion from nuclear energy, wherein thermal efficiency is less 30% in comparison to direct conversion which should be higher than30%? Is it not possible that nuclear reaction can produce direct electricity?
  46. C

    Creating electricity utilzing water particles in a vacuum

    Hi. I'm a first year Engineering student at QUT here in Brisbane. My problem is I come up with all these great ideas but lack the confidence and skills to carry them through to realization. I am currently taking 6 months deferment from my degree due to the difficulty of the maths. I have this...
  47. TardisRobber

    Harnessing Electricity from an Electromagnetic field?

    Does anyone have any thoughts on what would happen if you tried harnessing Electricity from an Electromagnetic field?
  48. naiasetvolo

    Why do we want to know how much a charge can be stored /V?

    Why do we want to know how much a charge can be stored per volt? What has the voltage to do with the storage of charge in a capacitor?
  49. D

    Power consumption in KWH of motor

    Homework Statement Hello Everybody, When i was searching for power required to lift an object, i found that:- For Example, Q :- 100 kgs to be lifted 3 metres in 5 seconds. (vertical) A :- Mass * Gravity * (Distance / Time) = 100 * 9.8 * (3/5)...
  50. N

    Electrostatic discharge current

    I understand that electrically charged objects such as a rubber balloon or even the human body can hold several thousands of volts. What's troubling me is that I know the current that results from an electrostatic discharge is not enough to cause serious damage or kill a human, yet if you touch...
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