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.

View More On Wikipedia.org
Recent contents Top users
  1. J

    What do you call Generation of electricity using waste heat

    What do you call Generation of electricity using waste heat from processes to make steam and drive generators
  2. thegreengineer

    What does 0 V exactly mean in an electric circuit mean?

    I'm a mechatronics engineering student, and I know that electronics is a requirement in most engineering programs. I'm been dealing with electronics recently and I've been studying electric circuits. I've been noticing that in some of them instead of being closed (in diagrams) they are like...
  3. B

    How do I reduce the amount of voltage in a circuit?

    Hi, I'm having a difficult time understanding how voltage is reduced in a circuit. I know the relationship of V= IR, but I still don't understand. I think part of the reason I do not understand is the wording used, and the other part is from experience. For example if I have a fan that only...
  4. G

    Do birds on transmission lines experience electric shock?

    Gruxg has posted a thread on November 4, 2012, titled as "If you touch a live wire without touching the ground, do you get an electric shock?". I think that this thread would deserve more consideration as it discusses an essential subject but unfortunately it is closed for further replies, so I...
  5. X

    Engineering Solving a weird circuit using nodal analysis?

    Homework Statement Homework Equations V=IR Kirchoffs Current Law The Attempt at a Solution I picked the middle node (the one surrounded by 3 resistors) as my reference. V1 and V2 are my other two nodes. I'm also assuming that V1>V2, V1<reference Using Kirchoffs Current Law: (Node 1)...
  6. M

    Charge flowing through/across a Capacitor?

    Homework Statement Dry air has a resistivity of about 3*10^13 Ωm. A capacitor has square plates 10cm on a side separated by 1.2mm of dry air. The capacitor is charged to 250V. Assuming the potential difference does not change as the charge flows, what fraction of the charge will flow across the...
  7. patrickbotros

    Why does a Charge Outside a Surface Produce No Net Flux?

    My textbook says "the net flux is zero through a closed surface that does not contain any net charge," and justifies it by saying that everything flowing in has an equal thing flowing out. This makes ABSOLUTELY NO sense to me.
  8. T

    What is the Rate of Tungsten Evaporation in a Light Bulb?

    Homework Statement Ina light bulb, billions of electrons flow through the tungsten wire bumping around, causing the filament to glow hot. Hot tungsten evaporates slowly, so its initial thickness profile r(x, t=0) can change over time. Consider a volume V of tungsten, with N bonds total, each...
  9. L

    Operating Torque out of Flywheel

    Homework Statement Hello, we have built a system in which energy is harvested through the use of an oscillating fin, this energy is stored within a flywheel which operates at a frequency f, we are then connecting this flywheel, via a smaller gear (gear ratio = 10) to an induction motor which...
  10. F

    Can Energy Be Recycled Using This Setup?

    Im doing a project on school. I want to re-use energy. I know that it will not run forever (but i hope it runs very long). So i wanted to ask if the image below is right and i could use it at school. If it shouldn´t work please say what i can make better. Thanks for your Help! Here is my image...
  11. D

    What happens if "hot" wire touches Earth ground?

    Greetings !New to the forums. Here expanding my concept of what AC Electricity is My question (correct me if wrong).. If AC power alternates between +,- at a rate of 60Hertz/second and negative is used as -earth- at the AC generator If the hot wire touches the ground would happen? (I think...
  12. S

    Impact speed of an electron in a parallel plate capacitor

    Homework Statement The electric field strength is 2.50×104 N/C inside a parallel-plate capacitor with a 1.20 mm spacing. An electron is released from rest at the negative plate. What is the electron's speed when it reaches the positive plate? Homework Equations F = eE = ma vf2 = vi2 + 2ad...
  13. dexter_95

    Charge Rod Experiment: Why Didn't My Hand Neutralize?

    In the charged rod experiment, why didn't my hand neutralize the charge formed in the rod, since my body is a conductor and it is connected to the Earth?
  14. AdityaDev

    Measuring resistance using potentiometer

    Homework Statement Homework Equations For R, current I=E/R and for X, I=E/X... both are separate cases. The Attempt at a Solution [/B] Why does the balancing change? The potential difference across each resistor is E Itself right? I tried by assuming an arbitary internal resistance r...
  15. P

    Is the Scattered Voltage Data in My Experiment a Result of Measurement Error?

    I'm doing a quality of measurements coursework at the moment, the coursework was to find the efficiency of a kettle, and to do this, one of the factors that I needed to find was the voltage. So in 300ml of water, the voltage was 240.5V 400ml - 244V 500ml - 243V 600ml - 245V 700ml - 241.4V...
  16. Zanker

    Electric Field & Potential of infinite concentric cylinders

    Homework Statement Consider an infinitely long solid cylinder of uniform linear charge density λ1 and radius a inside a hollow cylindrical pipe of inner radius b and outer radius c and uniform linear charge density λ2. A cross-sectional view of the system is shown below(linked and attached)...
  17. P

    Static Electricity corrupting electrical equipment

    I need help. I am installing new networked alarm panels throughout a building. There is a room where one panel is and that panel is continually having components fail. While in this room it is also very common for me to receive a static shock when coming in contact with any metal. I realize...
  18. S

    Can reflected light help generate electricity with a solar panel?

    Can we use a mirror to reflect sun's light on a solar panel and generate electricity?
  19. X

    Why is the voltage across one resistor the same as supply?

    People say that the voltage across one resistor is equal to the voltage supplied. I've drawn a picture of a simple circuit with two points near the positive terminal. Apparently, if we take the potential difference of these two points, it will equal 9V according to the above saying (which can...
  20. X

    Work done assembling a system of charges?

    This is a concept that has long since plagued me. I will quote an article off of Google about the concept I am confused about: "Consider a collection of static point charges located at position vectors (where runs from 1 to ). What is the electrostatic energy stored in such a collection...
  21. C

    What causes changes in electric field within a circuit?

    So I'm having trouble visualizing how voltage drops more within different parts of a circuit, such as a resistor vs. wire. I know all the general equations but the concept is hard for me to comprehend and I am stuck on one notion. So, say you have a simple DC circuit with just a resistor and...
  22. P

    Tap Changing (ULTC) Transformers and Reactive Power Control

    So I am trying to understand how a ULTC operates in the Reactive Power Control mode (it adjusts taps to control the reactive power in a line). What equation is governing it's operation, and what variables does it adjust in order to increase/decrease reactive flow? Is it just the simple reactive...
  23. X

    Confusion about voltage in a circuit

    So basically, I am inferring the following based off of what I've learned. When we hook a battery up to a circuit, this creates a potential difference. Say we use a 9V battery. Here is a picture: From what I know, the horizontal is a equipotential surface, and the vertical has different...
  24. Domenico94

    Diodes Exercises: Engineering Student Seeks Help

    HI everyone. I'm an engineering strudent, looking for online material with exercises on diodes...anyone can send me a link here with explanations of the various exercises? Thank you very much :)
  25. S

    Why can not we generate electricity with magnets?

    If we can create a magnetic field with a solenoid, why can not we generate electricity with magnets?
  26. X

    Does a constant magnetic field cause a current?

    (1) I previously learned that a constant magnetic field causes a force on any electrons within its range. Clearly, this force would cause electrons to move. Isn't this creating a current? (2) However, now apparently I am told that the only varying magnetic fields can create a current. I.e...
  27. X

    Can electrons "fly" between capacitor plates?

    How exactly do the electrons move from the capacitor to the rest of the circuit? Do they fly between the capacitors plates, or can they only travel where there is a wire connection? (I.e., if a small chunk of our circuit looks like this: A-------| |-------B can an electron start from A, go to...
  28. X

    Why does the potential difference between two capacitors seek equilibrium?

    Suppose we have a circuit with two capacitors connected to each other, C1 and C2. C1 is charged and has a potential difference of 5 V (V1=5V), but C2 is not charged (V2=0) Apparently it is known that the potential difference of these two capacitors will want to reach equilibrium. So V1=V2...
  29. AdityaDev

    Calculating Heat Generated in a Coil due to Changing Current and Resistance

    Homework Statement What amount of heat will be generated in a coil of resistance R due to a charge q passing through it if the current in the coil decreases down to zero uniformly during a time interval ##\Delta t## Homework Equations ##dH=i^2Rdt## ##i=\frac{dq}{dt}## The Attempt at a...
  30. I

    EMF radiation shielding and dirty electricity

    Hello, Does anyone shield themselves from computer / monitor from EMF radiation? if so what materials do you use to cover/coat your electronics? I am buying an EMF meter soon (Trifield 100XE) and plan on solving all my EMF issues, specifically around my computer tower, monitor, and other...
  31. END

    Electric Field of Point Charges in Equilateral Triangle

    Homework Statement A point charge q =+6.4 \mu \mathrm{C} is placed at each corner of an equilateral triangle with sides 0.29 \mathrm{m} in length. What is the magnitude of the electric field at the midpoint of any of the three sides of the triangle? Hint: if you are careful to examine the...
  32. P

    Power dissipated by a resistor in a circuit

    Homework Statement Homework Equations P = V^2 / R 1/Rt = sum(1/Ri) (parallel) The Attempt at a Solution [/B] Since all the answer choices express the solution in terms of V^2 / R, I tried to find the voltage drop across resistor #2 to find the power. I collapsed the two parallel...
  33. S

    Where between two charges does voltage = 0?

    Homework Statement If Q1 in the above figure is twice Q2 and both are positive, where can a point of zero potential be found?Homework Equations V = kq/r The Attempt at a Solution I know that eventually I'll have to set it up so that kq/r = kq/r, but my problem is, how do you know where this...
  34. S

    Net Electric Force Homework: Find Negative Charge Position

    Homework Statement [/B] In the above figure, if Q1 and Q2 are positive, where could a negative charge be placed and have a vertically upward net force on it? Homework Equations F = k|q||q| / (r^2) The Attempt at a Solution I wrote the force equations for the negative charge and both positive...
  35. G

    Can anyone explain me this circuit

    http://prntscr.com/60xcwx Thank you
  36. S

    Calculate the equivalent resistance

    Homework Statement Ignore the internal resistance of the battery and assume it is merely a battery. Calculate the equivalent resistance of the circuit. Homework Equations 1/Req = 1/R + 1/R ... (parallel) Req = R + R ... (series) The Attempt at a Solution I know this is fairly simple but I...
  37. X

    Why isn't current negative in this example?

    Homework Statement The figure gives the electric potential V(x) along a copper wire carrying uniform current, from a point of higher potential Vs = 9.00 μV at x = 0 to a point of zero potential at xs = 3.20 m. The wire has a radius of 1.50 mm, and copper has a resistivity of 1.69 × 10-8 Ω·m...
  38. X

    Finding the voltage of a circuit

    Homework Statement Capacitor 3 in Figure (a) is a variable capacitor (its capacitance C3 can be varied). Figure (b) gives the electric potential V1 across capacitor 1 versus C3. The horizontal scale is set by C3s = 20 μF. Electric potential V1 approaches an asymptote of 10 V as C3 approaches...
  39. S

    How do Kirchhoff's Rules apply to a circuit with multiple resistors in series?

    Homework Statement [/B] Consider the circuit above. You are given the following measured values: V = 1.5 V R1 = 100 R2 = 100 R3 = 50 R4 = 50 R5 = 50 Homework Equations Kirchhoff's Loop Rule and Junction Rule The Attempt at a Solution I tried setting this up using the junction and loop...
  40. N

    Question about electricity towers and poles

    I have several questions about poles and towers. a. Does all of transmission towers carries three-phase powers? Is there no transmission towers designated for single-phase? b. Does all towers are for transmission purposes only? Is there any towers in the world used for distribution instead of...
  41. X

    Why is work done by a nonconservative force negative

    In my textbook it says that work done by a nonconservative force (an applied force) has the same sign as the change of potential energy? For instance, if I push a positive test charge from an infinite distance away to a negative charge, then the test charge goes from high potential energy to...
  42. Domenico94

    Solar panels and optical parametric oscillator

    Hi everyone. On these days, by watching solar panels and similar stuff, I just thought about it, and why they take such a wide surface to produce energy, and why their output is often low, as we all know. By navigating here on the internet, I've just seen a device called OPO (Optical...
  43. J

    Capturing Tiny Amounts Of Electricity At A Time?

    A small thermocouple would produce tiny amounts of electricity as temperature unevenly fluctuates. But if I tried to store that energy using a diode and capacitor, I would guess that the tiny reverse current flow through the diode would be enough to not allow for such a self charging system to...
  44. Y

    Magnet/Electricity to rotate object 90 degrees?

    Hello, I want to create a motion using electricity, using the cheapest means possible (DIY). Basically I'm trying to rotate an object 90degrees when the current is on, and back to its original position when the current is off. The questions are: 1) Is this possible? 2) Can this be done using...
  45. M

    Velocity of electrons in a wire

    Electrons are moving in moves in all sorts of directions, causing the net electric charge to cancel out. But, when you apply a voltage, there's a small amount of electrons that will move towards the direction in the direction of the voltage. This is called the drift speed. Am I right? I read...
  46. B

    Question about the RLC circuit

    In the direct current circuit, when you have a switch and you turn it on, you get the coil to generate a current to the opposite direction but the magnitude isn't big enough to offset the main one. But in the case of alternating currents, the coil seems to generate enough current up to the...
  47. F

    Electricity: Resistance and temperature

    Hi everyone, I just came across an exercise that asks me to explain how I would measure the change of resistance of a metal wire between a temperature of 0º C and 100º C. The answer to the question is below, what I don't understand is why is there a need to put ice in the water bath and the need...
  48. N

    Understanding Household Electrical Service Lines and Safety Precautions

    Pardon me if I stated the title incorrectly/ informally. I just want to say about the title is about the 220 V, 60 Hz source (present in our outlets also) in our house by which comes from nearby electrical post. I have four questions in this post/thread so kindly tell me if I need to edit this...
  49. B

    How can I get wind powered electricity in my home?

    I currently get my electricity from an electric company. I would like to get a windmill installed on my roof to supplement my electricity needs. I want to be able to use the windmill to get as much free electricity as I can, and I would like to continue to keep getting the rest of the...
  50. D

    A microscope in an electricity laboratory

    Is there any usage for a measuring microscope in an electricity laboratory as a part of any experiment? We have a Mitutoyo measuring microscope in our fundamental electricity physics lab which is a course for sophomores. We used it for apparent depth in our optics lab which is retired now! I'm...
Back
Top