Electric Definition and 1000 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

    Electric field due to two positive charges

    I am having trouble solving the following problem. I am given two positive charges on the x axis: I know that the electric field strength at point P is ##E=150 \frac{V}{m}##, ##d=1.8m## and ##a=2.5m##. I want to find the charge of ##Q##. As far as I know, the electric field on the y-axis...
  2. R

    Electric field on a ring's axis

    The contribution coming from a little segment of the ring is ##d\vec{E}=\frac{dQ}{r^2}cos\theta \hat{z}##, assuming that the horizontal components cancel out. But how can we show that?
  3. navneet9431

    Would electric field exist if there were only one type of charge?

    I believe the answer is incorrect, reasons: The answer assumes that electric field will exist . But this is not the case , until and unless there is a bipolarity there cannot be an electric field ( in case of isolated charged objects, the field exists because the bipolarity is separated by a...
  4. Zahid Iftikhar

    Electric Field of a moving charge

    When a charge is at rest, it has an electric field only. When the charge starts moving , it is said to have accompanied a magnetic field. My question relates to its electric field while in motion. Does it still exist or not? I know in electron guns electrons are deflected while passing thru the...
  5. S

    How to measure electric and magnetic fields in asymmetric capacitors?

    Summary: I need to build an asymmetric capacitor, but the mathematics of electromagnetics become too tough, do you have any info that can help? Appreciate it! Hello, I am an undergraduate student in engineering and I want to build an asymmetric capacitor, so I need electromagnetics which I...
  6. J

    Electric Field for Charge Distributions

    We are given: q1 = +2.0 x 10-5 C, q2 = q3 = -3.0 x 10-5 C, r31 = r21 = 2 m a) We start by finding the electric force between q3 to q1 and q2 to q1 FE31 = k * q1 * q3 / r312 FE31 = (9.0 x 109 Nm2/C2) * (+2.0 x 10-5 C) * (3.0 x 10-5 C) / (2 m)2 FE31 = 1.35 N FE21 = k * q1 * q2 / r212 Since...
  7. P

    Calculating a Non-Uniform Electric Field Given 6 different Electrode Pairs

    I know how to find the electric field of more traditional designs i.e. a sphere, through Gauss' Law but I don't think Gauss' Law applies to this scenario. I tried to separate each part of the electrode into simple spheres and rods and using Gauss' Law to find these individual elements. This...
  8. K

    Electric Circuts (Voltage, Ohms, Amps)

    I made a chart and this is my attempt. I am not sure that I am doing the calculations right thou
  9. merlyn

    The phase of electric and magnetic forces in a photon.

    I'm curious if someone help me understand why the electric and magnetic forces are IN PHASE at right angles to one another? Should they not be 90 degrees out of phase in order to conserve energy? I do understand they are in phase but why? Thank you all for your time. Merlyn.
  10. C

    Small doubt regarding electric charge

    Good morning I'm no expert in classical physics, so I have one doubt. If I have a body with mass M, and I charge it electrically with x C (Coulombs), will its mass remain the same, or will it change (in which amount)? Can you help me in the case of a ball, let's say, with 1.5 Kg charged with...
  11. Anand Sivaram

    Question About Electric Aircraft Propulsion

    I have been thinking about this subject for some time now, based on the following considerations 1) Many companies are working on Electric Aircraft Propulsion, high energy density Li-Ion batteries are used to power Electric motors and they drive propellers. This is the approach every one is...
  12. C

    The source of the electric field of a battery?

    If you place a zinc / copper battery it will create an electric field pointing from the copper to the zinc and my question is this what makes this electric field , the zinc pushes electrons in the circuit and never "stays" negatively charged for an electric field to be created same for the...
  13. S

    Find the charge of a mass hanging from a pendulum in an electric field

    Hi, so I was able to solve this problem by just equating the forces (Tension, mg, and EQ). But I thought I could also solve this problem with Conservation of Energy. However, I calculated it several times, and I never get the right answer this way. Doesn't the Electric Field do the work to put...
  14. Physics lover

    Variation of electric field and potential along the axis of a cone

    Options are at the top of page as a) b) c) d) Answer may more than one. Now since 'a' is distance from the smaller surface of cone so as we move along the axis area will increase,So current charge density will decrease and as we know J=sigma E,E will decrease,but V will remain constant since...
  15. M

    Electric field in a circuit with a DC source

    So I understand that when an electric field is produced in a conductor of length L, the net electric field in the conductor will be 0 because the rearrangement of electrons in the conductor results in the production of its own electric field which cancels out the one produced initially...
  16. T

    Solving for Electric Field at an Angle: Ex = 10.0V/m

    Ex =10.0Vm-1 dx= d2=x2+y2 x=4.00m y=3.00m d2=4.002+3.002 d=5.00m Ex = -dV/dx 10.0Vm-1=-dV/5.00m 10.0Vm-1*5.00m=-dV -50.0V=dV So from origin at 100V-50.0V = 50.0V But the solution I am given gives the answer at 50.5V and the information "directed at 45.0◦ " does not seem to have been used so may...
  17. N

    Could Radioisotope Thermoelectric generators power electric cars?

    Could electric cars be given longer range by radioisotope thermoelectric generators like they use to power spacecraft in deep space?
  18. Pushoam

    The electric field inside and outside of a dielectric

    I bring a dielectric in a region with electric field ##\vec E_0##. Net electric field ## \vec E_{net} = \vec E_0 + \vec E_p ## , where ## \vec E_p ## is electric field due to polarization of dielectric. For linear dielectric, ## \vec E_p ## is 0 outside the dielectric. So, ## \vec E_{net} =...
  19. Z

    B Why are there only two types of electric charge?

    Why are there only two types of electric charge? I'm asking as a total layman in science. I've started to wonder about this the more I watch popular science videos about the Standard Model of particles physics and about matter and antimatter. In particular, the various types of subatomic...
  20. A

    How to stop a steering wheel using an electric motor?

    Problem Statement: i have a steering wheel mounted on an electric motor, and i want to stop the driver from going beyond a certain angle. i can read the torque applied by the driver, and the steering wheel angular velocity as well. how can i stop the steering wheel, without sending it harshely...
  21. H

    Strange question about cancelling electric fields

    I am curious about the case where two electric or magnetic fields cancel each other out (I'm assuming this is possible). If a charged particle travels through the region where the cancellation exists, I am assuming the particle behaves as if no field exists. Does that area still have electric...
  22. H

    Do electric fields have their own separate inherent charge?

    I am assuming the answer is NO. I realize that the electric field of any charged object has an energy density, but I was curious to know it that same field has it's own 'charge density' so to speak, and that it would have a small secondary electric field of it's own. This would imply that...
  23. E

    Draw an electric circuit potential graph

    Hi. I have physics homework that I don't understand. Hopefully, someone here can give me some advice. So, the homework goes like this: Draw an electric circuit potential graph and find out the potential difference between points B and C. The two resistors have equal values. Believe me or...
  24. H

    Energy Density of Electric Fields: Is it the Sum of All Electrons?

    I understand that the energy of an electric field arises from the work put into gathering the electrons together to create the field. Bringing electrons close together requires energy because they naturally want to repel. This potential energy is stored in the field itself and the field has an...
  25. DaTario

    Electric current being alternated with continuous part

    Summary: In which scenario a current may exhibit alternated and continuous character together? Hi All, I would like to know in which scenario an electric current may exhibit alternated and continuous character? Something like $$ I(t) = I_0 \sin (\omega t) + I_1 $$.
  26. alexmahone

    Average electric field over a spherical surface

    I'm sure the average is going to be an integral, but \displaystyle\frac{1}{4\pi R^2}\oint\mathbf{E}\cdot d\mathbf{a} gives me a scalar, not a vector.
  27. M

    Finding the maximum value of the electric field

    I tried to find it the following way but to no avail: Let maximum value of ##\sigma## be ##S## Now unfortunately, we do not have a maximum value for ##\dfrac{1}{r^2}## because the field point can be as close as we want to the arbitrary surface charge. (The field at a point on the surface is...
  28. dRic2

    Simple electric potential and Laplace equation

    Imagine to be in 2 dimensions and you have to find the potential generated by 4 point-charges of equal charge located at the four corners of a square. To do that I think we simply add all the contributions of each single charge: $$V_i(x, y) = - \frac k {| \mathbf r - \mathbf r_i|}$$ $$ V(x, y)...
  29. fight_club_alum

    Particle that moves in an electric and magnetic field

    m = 0.005 q = -70 x 10^-6 c v = 30,000 m/s Since there is no movement vertically Fb = Mg So, q . V . B = mg So, (70 x `10^-6) . (30,000) . B = (0.005) . (9.8) So, B = 0.0233333 or ~ 23 MT
  30. J

    Why don't electric motors use exciter coils like generators do?

    I remember (long ago, in college physics) learning about electric motors and generators, specifically about the "exciter" coils in generators which did a better job than permanent magnets, because of a sort of "turbo" or force-multiplier effect. I notice, however, that while basically ALL...
  31. C

    Why Does a Static Electric Discharge Make a Sound and Light?

    Since electrical charges causes a sparkle or a crackle which is light and sound. Also light and sound are forms of energy does that mean that electrical discharge releases energy and if yes then the release of energy have an effect on charge
  32. K

    Clarification of electric potential difference

    I have some questions regarding the sign of potential difference. For example, given the literal definition as the difference in potential between two locations it should be possible for potential difference to be negative if the final potential is less than the initial, but while reading texts...
  33. Kasiopea

    Why is the x-component of the electric field at point P positive?

    I got the answer: E(P)=(k*Q)/(3î )−(k*Q*ĵ) /2 Can someone confirm if this is the right answer?
  34. jmemo

    Find the direction and magnitude of an electric field

    Find the direction and magnitude of an electric field that exerts a 4.65 ✕ 10−17 N westward force on an electron. (Enter the magnitude in N/C.)
  35. R

    Divergence of an Electric Field due to an ideal dipole

    Given $$\vec E = -\nabla \phi$$ there $$\vec d \rightarrow 0, \phi(\vec r) = \frac {\vec p \cdot \vec r} {r^3}$$ and ##\vec p## is the dipole moment defined as $$\vec p = q\vec d$$ It's quite trivial to show that ##\nabla \times \vec E = \nabla \times (-\nabla \phi) = 0##. However, I want to...
  36. somasimple

    Ion migration by diffusion in an electric field

    Hi, A solution contains some ions (charged particles). We are only interested in my exemple to positive ions. It is assumed that these ions acquired some mobility under a concentration gradient. Their direction is A to B. Then these ions encounter/cross an electric field which is oriented from B...
  37. M

    What will the electric field be at the surface?

    The electric field due to a dipole distribution in volume ##V'## can be viewed as electric field due to a volume charge distribution in ##V'## plus electric field due to a surface charge distribution in boundary of ##V'##. ##\displaystyle\mathbf{E}=\int_{V'} \dfrac{\rho...
  38. M

    What is the continuous electric dipole distribution?

    An electric dipole is a system of two opposite point charges when their separation goes to zero and their charge goes to infinity in a way that the product of the charge and the separation remains finite. Now how can we have a continuous electric dipole volume distribution from such a...
  39. A

    Most efficient way to drive an electric car and why?

    Hello, I wanted to get a physics analysis of the best way to drive an electric car for maximum range. For example, would it be more efficient to drive on side streets at a slower speed of say 30 mph, or would it be better to get on the freeway and drive 60. Should I be accelerating as slowly as...
  40. Eucliwood

    Theoretical vs measured electrical resistance: Percent error relation

    Mentor Note -- Thread moved from the technical forums, so no Homework Template is shown. So, we've conducted an experiment on resistors in a circuit. The theoretical calculation was based of on E-24 series color band table and the measured resistance of the resistor was measured by a meter...
  41. Gnall

    How could I find the total electric field in this question?

    The electric field due to the semicircle is 2kQ/pi.Rsquare Sorry for the bad english.
  42. hagopbul

    A question about how to protect a battery of an electric car?

    Hello all: I have a question about electric car battery ? What is the best charging method for the battery ? Is it high ampere charging or high voltage charging ? Thanks in advance H
  43. Aryamaan Thakur

    Electric potential at the edge of a thin charged circular plate

    My question might sound stupid to you but please clear my confusions. I'm taking an circular arc like element on the plate. That arc has a radius of 'r' (AB) and the radius is inclined at an angle 'θ' with OA (∠OAB). The area between arc of radius r and r+dr is dA. dA = 2θr.dr The charge on...
  44. peguerosdc

    [Griffiths ex4.2] Electric field of a uniformly polarized sphere

    Hi! This is more a conceptual question rather than the calculation itself. So, Griffiths' section 4.2.1 "The field of a polarized object / Bound charges" says that if you want to calculate the field produced by a polarized material, you can find it from the potential of a surface charge and a...
  45. P

    Electric Field Lines: Should Earthed Plate Have No Charge?

    Shouldn't the plate that is earthed be with no charge? making B correct. but the accepted answer was A.
  46. cianfa72

    Electric potential difference between a battery's + terminal and the ground

    Hi, I've a question about electricity in the following scenario: consider an accumulator (e.g. a 9V battery) and an analog/digital voltmeter having a probe connected to the accumulator + clamp and the other to the ground (for instance connecting it to a metal rod stuck in the ground). Do you...
  47. Y

    Problem concerning a mass with charge in a homogeneous electric field

    I know how the answer is C, since E=F/q and F=ma=mg. However, I am a bit confused as to why my other method doesn't work. I thought that since the droplets are falling at a constant velocity, there is not net force, so according to E=F/q the electric field must be zero then? This seems like a...
  48. K

    Electric field problem — Changing the charge on two spheres

    Two identical conducting spheres A and B carry equal charge. They are separated by a distance much larger than their diameters. A third identical conducting sphere C is uncharged. Sphere C isfirst touched to A, then to B, and finally removed. As a result, the electrostatic force between A and B...
  49. Zack K

    Electric field of a hollow cylinder

    I uploaded a diagram of the problem. I treated this as many thin rings and integrated it over the length. I placed my origin as in the same place as the uploaded picture. Finding the electric field due to one small ring: ##\vec r =\langle w-x, 0, 0 \rangle## where ##x## is the distance of the...
  50. archaic

    Is the 'test charge' in electric potential energy defined as immobile?

    Hello, quick question, when EPE was defined, did we decide that the "test charge" is immobile in the field? Otherwise a force equal and opposite to that of the electric field would just stop the charge from accelerating.
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