What is Charges: Definition and 1000 Discussions

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charge: positive and negative (commonly carried by protons and electrons respectively). Like charges repel each other and unlike charges attract each other. An object with an absence of net charge is referred to as neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum effects.
Electric charge is a conserved property; the net charge of an isolated system, the amount of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms. If there are more electrons than protons in a piece of matter, it will have a negative charge, if there are fewer it will have a positive charge, and if there are equal numbers it will be neutral. Charge is quantized; it comes in integer multiples of individual small units called the elementary charge, e, about 1.602×10−19 coulombs, which is the smallest charge which can exist freely (particles called quarks have smaller charges, multiples of 1/3e, but they are only found in combination, and always combine to form particles with integer charge). The proton has a charge of +e, and the electron has a charge of −e.
Electric charges produce electric fields. A moving charge also produces a magnetic field. The interaction of electric charges with an electromagnetic field (combination of electric and magnetic fields) is the source of the electromagnetic (or Lorentz) force, which is one of the four fundamental forces in physics. The study of photon-mediated interactions among charged particles is called quantum electrodynamics.The SI derived unit of electric charge is the coulomb (C) named after French physicist Charles-Augustin de Coulomb. In electrical engineering it is also common to use the ampere-hour (Ah). In physics and chemistry it is common to use the elementary charge (e as a unit). Chemistry also uses the Faraday constant as the charge on a mole of electrons. The lowercase symbol q often denotes charge.

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  1. V

    Electrostatic energy of three charges

    Homework Statement Two equal charges of magnitude Q each are placed at a distance d apart .Their electrostatic energy is E. A third charge -Q/2 is brought midway between these two charges .The electrostatic energy of the system is now A) -2E B) -E C) 0 D) E Homework Equations EPE = kq1q2/r...
  2. S

    How Does Current Direction Affect Magnetic Field Orientation?

    Homework Statement current in wire is in east to west direction.direction of magneetic field below the line Homework Equations right hand thumb rule The Attempt at a Solution i used the right hand thumb rule to find the direction of magnetic field but the magnetic field comes out in in the...
  3. chopnhack

    Two point charges repelling, stretching a spring

    Homework Statement Two spherical point charges each carrying a charge of 40 mC are attached to the two ends of a spring of length 20 cm. If its spring constant is 120 Nm-1, what is the length of the spring when the charges are in equilibrium? Homework Equations 1) F = k*(q^2)/r^2 where k is...
  4. chopnhack

    Point charges in a equilateral triangle - typo in solution?

    Homework Statement Three point charges each carrying a charge of 11.0 µC are located at the corners of an equilateral triangle of side 15.0 cm. Calculate the magnitude and direction of the force on each charge. Homework Equations k = 9.0x109NM2C-2 F = k⋅(Q1⋅Q2)/r2 The Attempt at a Solution...
  5. joerylee palmerola

    Electric field due to a point charges

    Suppose a charge q is placed at point x=0, y=0. A second charge q is placed at point x=8.0m, y=0. What charge must be placed at the point x=4.0m, y=0 in order that the field at the point x=4.0m, y=3.0m be zero?
  6. P

    Does the first Maxwell equation work also for moving charges?

    My professor said that the first two maxwell equation's are about static fields Another fast question: Do a single charge that is moVing generate a magnetic field? I saw a demonstration that explains the magnetic field as an electric field using only special relativity, there is a free charge...
  7. G

    The total potential energy of two charges Wikipedia mistake?

    Say, we have two particles of equal and opposite charge in an isolated system in which we neglect gravity. The energy of particle 1 is: E1 = U1 + T1 Where U1 is electrostatic potential energy and T1 is the kinetic energy of particle 1. The energy of particle 2 is: E2 = U2 + T2 Where U2 is...
  8. N

    How does a battery push charges? Potential difference?

    Hello there, I'm confused on several things such as the potential difference it provides and how it pushes the charges through the wire or conductor or circuit. So when a battery comes into contact with a wire, the positive charges flows from high potential through the circuit to the low...
  9. Y

    What do you mean by force "between" two charges?

    I can understand force being exerted by an object on another object but I can't understand what all this force between two objects is. Can anyone give the complex and simple explanation, please? I am completely freaking out not being able to understand. Analogies and visualizations are a great...
  10. alv

    Charges in Magnetic Fields from Surfing Physics book

    I am a teacher and I can't work this one out. I am trying to answer (a). I have only included the further parts of the question (b, c and d) so you can see why some parts of the question are included. A single positively charged particle, mass 4.6 x 1027 kg, enters a 4.0 T magnetic field into...
  11. B

    Equilibrium of Charges at Circumference of a Circle

    Homework Statement Two charges placed at circumference of a circle of radius ##a## at ##\pi/2## from each other. Find the relative magnitude of third charge kept on the circumference such that the system is at equilibrium.Homework Equations Coulombs law. The Attempt at a Solution Let ##Q##...
  12. dbuhtoia

    Electric field with three charges and a point

    refer only to the image above, not the question 4.) Two point charges, Q1 and Q2, are placed 0.30 m apart on the x–axis (shown in the figure above) Charge Q1 has a value of –2.50 x 10–6C. The net electric field at point P is zero. a. What is the sign of charge Q2? ____ Positive ____...
  13. RabbitWho

    Finding the force of repulsion between two point charges

    Hello! So this is going into physics because it is a physics problem, but it is maths that is the real problem. So if you came here to help someone with physics and not maths I'm sorry. 1. Homework Statement Find the force of repulsion between two point charges of +1C and +3C if they are...
  14. K

    Electric field created by point charges and conducting plane

    I came upon this: http://physics.stackexchange.com/questions/174514/will-the-electrostatic-force-between-two-charges-change-if-we-place-a-metal-plat/323006#323006 question on Physics Stackexchange which I found very interesting. The configuration is basically two positive point charges q and...
  15. A

    There are two charges with charge q and mass m

    There are two charges with charge q and mass m and they are in equilibrium. Then, in the diagram why is my teacher saying that electrostatic force(F)=mg? Below is diagram.
  16. Berker

    Motion of 4 charges positioned in a square shape

    Homework Statement Four particles with equal charges q and equal masses m are placed on a plane so that they form the corners of a square with side length a. The charges are then released from rest at this configuration (shown as (i) in the figure). After the release, the particles accelerate...
  17. S

    Dielectric Charges: Explaining Why They Don't Attract

    can someone in detail explain to me why can't a dielectric attract charges?
  18. danielhep

    MasteringPhysics: Find the angle between the point charges.

    Homework Statement Two m = 4.0 g point charges on 1.0-m-long threads repel each other after being charged to q = 80 nC , as shown in the figure. What is the angle θ? You can assume that θ is a small angle. Homework Equations Fe=kq2/r2 F=ma Fg=mg The Attempt at a Solution Equation 1:[/B] r =...
  19. S

    Why Can a Positive or Negative Charge Attract a Neutral Object?

    Can someone in detail please explain to me why a positive or negative charge can attract to a nuetral object?
  20. Don Bones

    Force from "like charges" with and without movement

    I apologize ahead of time if this thread was made in the incorrect post. I have only taken Physics III (Mechanics) and am now taking Physics IV (Electricity/Magnetism). I have yet to find a description of every type of forum here. In class, I was understanding everything that was mentioned and...
  21. W

    Resultant Electric field between charges

    Homework Statement A +15 microC point charge Q1 is at a distance of 20 mm from a + 10 microC charge Q2. Fin the resultant electric field at: Ai) the midpoint between the two charges ii) at point P along the line between Q1 and Q2 which is 25 mm from Q1 and 45 mm from Q2. bi) Explain why...
  22. T

    Deriving an expression for the energy required to separate charges

    Homework Statement Hi guys, would just too make sure my derivation and insight to why is correct. Question: a) only Homework EquationsThe Attempt at a Solution $$dU=-wd_{ext}$$ $$dU=-F_{ext} \cdot dx$$ Now as the ##F_{ext}## is in the same direction and the direction vector { have not...
  23. Albi Mema

    Forces between the dipole and a point charge

    Homework Statement We have an electric dipole with moment P=2*[10][/-5] pointing in x direction. What is the force experieced by dipole at origin when a point charge Q=3*[10][/-4] is located at (0.014 m ,0,0) Homework Equations 1. [E][/dipole]=(1/4π[ε][/0])(2p/r3) 2. p=qs 3. F=qE 4. τ=pEsinϑ...
  24. BrainMan

    Continuous Distribution of Charges Problem

    Homework Statement Charge Q is uniformly distributed along a thin, flexible rod of length L. The rod is then bent into the semicircle shown in the figure (Figure 1) . Find an expression for the electric field E⃗ at the center of the semicircle. Hint: A small piece of arc length Δs spans a...
  25. M

    Difference Electric Field Strength Point Charges vs. Plates

    Why does the electric field strength on a straight line (E = k.(Q1/d12+Q2/d22). D1,2 = distance with respect to Q1,Q2) between two point charges vary with the location on this line while the field strength between two parallel plates which remains the same anywhere between the plates...
  26. D

    Calculating the Potential Energy of a 3-point charge config.

    Homework Statement Charge q1= 8.5 nC is located at the coordinate system origin (0,0), while charge q2= -4.46 nC is located at (a,0), where a= 1.5 m. The point P has coordinates (a,b), where b=0.95 m. A third charge q3= 16.5 nC will b added later. It is a 3 part question, first asking for the...
  27. S

    Moving charges and varying magnetic fields

    I understand that a steady flow of current will not induce currents in near by conductors. But, what about a steady flow of current that is being accelerated perpendicularly by a uniform magnetic field? Wouldn't this current produce a time varying magnetic field? This is a conductive disk with...
  28. E

    B Does a moving bar magnet create charges?

    So I understand that a charged particle moving relative to me has a magnetic field, and does not have one if its stationary relative to me... So is it true that a magnet moving relative to me has a charge? Say I took a bar magnet and threw it away from me way out in space, would it acquire a...
  29. M

    Six identical charges in hexagonal setup problem

    Homework Statement Attached the original script. Sorry but I don't know how to type in latex so its easier to attach photos. Homework Equations ET=Σ6n=1En The Attempt at a Solution I attached what I was able to do, I know there is a mistake is in part (b) that I can't locate and any help or...
  30. J

    Charges inside a metal sphere will tend to go towards

    Homework Statement A metallic sphere is charged. Where will the charges go? At center or on surface or uniformly distributed. Homework Equations I think it should be uniformly distributed. Cause that's why we have terms like volume charge density like we do q/volume. The Attempt at a Solution...
  31. tarkin

    Electric Field due to multiple point charges

    Homework Statement [/B] Derive expressions for the magnitude and direction of the electric field at point P and the potential at R. Charges Q1 and Q2 are both positive. Distance from Q1 to P is h, distance from Q2 to P is √2 h Homework Equations E = k q/r^2 The Attempt at a Solution I...
  32. T

    Classical mechanics electrostatics and charges

    Homework Statement hi i was doing a practice physics junior olympiad paper when i got stuck in question 11 in this link [/B] https://www.scribd.com/document/244111815/SJPO-2013-Special-Round-pdf Edit by moderator: Inserted relevant extract of the PDF so that helpers do not have to...
  33. P

    Electric field at a point affected by two charges

    Homework Statement (a) What is the strength of the electric field at the position indicated by the dot? (b) What is the direction of the electric field at the position indicated by the dot? Specify direction as an angle measured ccw from the positive x-axis. ##Q_{1} = 4.0 C## ##Q_{2} = 9.0...
  34. C

    Getting direction of force of two point charges on a third

    Homework Statement What is the direction of the force F on the -10 nC charge in the figure? Give your answer as an angle measured cw from the +x-axis. Express your answer using two significant figures. Homework Equations ##F = k\frac{Qq}{r^2}## The Attempt at a Solution I started by getting...
  35. W

    Capacitance and induced charges

    Homework Statement Two large parallel metal plates are oriented horizontally and separated by a distance 3d. A grounded conducting wire joins them, and initially each plate carries no charge. Now a third identical plate carrying charge Q is inserted between the two plates, parallel to them and...
  36. Ryan Sandoval

    Calculating Two Unknown Charges from a Tripole

    Homework Statement Written Problem: Summing the Electric Field Three point charges q1, q2, and q3 are placed along a straight vertical line to create a “tripole”. At point P, which is directly to the right of q1, the net electric field is exactly zero. We also know that q1 = 1 μC. b) Write a...
  37. V

    Given Two Point Charges, Find the charge at Point 0 as x,y

    Homework Statement Two point charges are placed on the x axis. The first charge, q1 = 8.00 nC , is placed a distance 16.0 m from the origin along the positive x axis; the second charge, q2 = 6.00 nC , is placed a distance 9.00 m from the origin along the negative x axis. Photo shown by...
  38. egio

    Exploring the Differences Between Electricity and Electrons/Charges

    Is electricity really the motion of electrons or charges? I'm kind of confused about the distinct differences. Any extra information would be greatly appreciated. I'd love to learn as much detail about this stuff as I can! Thank you!
  39. FallenApple

    Do charges accelerate because their field lines are changed?

    I ask this because of this diagram. Say that two charges are held a certain distance apart and are let go. Well, we see that the field lines of one charge repels the other. And I noticed that the field lines for an accelerating charge also bends. So can we say that because one field...
  40. RoboNerd

    Work done in assembling a system of charges

    Homework Statement Hi, everyone. I have a square and on each vertex of the square is a point charge of "+q". The square has a side length of "r" and these four charges form a system. My problem says to find the work required to assemble the charges shown above, bringing each charge in from...
  41. Tanmay Gupta

    Electric field question -- Charges....

    When a charge placed at anywhere,then it produces a powerful field around itself,is called electric field. It is exist whenever charge exist.And charge takes very very small time in propagate electric field.
  42. Schaus

    Electric potential at a point due to two charges

    Homework Statement What is the electric potential at P due to charges Q1 and Q2...
  43. O

    Why don't induced charges cancel each other out?

    If you bring a positive charge near a thin conducting sheet, it will induce a negative charge on the side nearest to the charge. And in order for the conducting sheet to remain electrically neutral, a positive charge of equal magnitude will be induced on the other side. How could the conductor...
  44. N

    I Magnetic Charges & Lorentz Invariance: Finding Papers

    How to find some papers on Lorentz invariant extensioning of standard electromagnetism that include magnetic charges
  45. Vitani11

    What type of charges in currents produce a magnetic field?

    Homework Statement Is a current that produces a magnetic field always going to be either an electron or a proton?
  46. T

    What charge would have to be fixed at the origin?

    Homework Statement A ball of mass m is attached to a rope of length L which has one end at the origin; the ball moves in a horizontal circle at constant speed v0 on a frictionless plane; the velocity is always at 90◦ to the rope. The ball has a charge q, and moves in a constant magnetic field...
  47. NihalRi

    Two point charges and electric potential difference

    Homework Statement In an experiment modeling point charges I had to find equipotential lines. I did so using a voltmeter. The results looked like this: Not a good quality picture, but the equipotential line on the right says 1.3 mV and the one on the left says 2.3mV. From this I had to...
  48. N

    I Understanding Weak Isospin in SU(2) Gauge Theory

    In QCD, quark is in fundamental representation of SU(3) and thus it has to have 3 charges (what we came to call "colors"). Gauge bosons are in adjoint representation and there are 8 of them. The choice how to assign color charges to them is not unique, one popular choice is based on Gell-Mann...
  49. S

    Magnetic Field produced by moving charges

    Homework Statement I have two related questions here. 1. A positive point charge is moving directly toward P. The magnetic field that the point charge produces at P is? 2. Two positive point charges move side by side in the same direction with the same velocity. What is the direction of the...
  50. A

    What Determines the Force on a Charge?

    Homework Statement I wanted to know how the charges knew their distance from each other. Homework Equations f=k(q1*q2)/r^2 The Attempt at a Solution I think it has something to do with the electric field lines that each charge outputs. But I'm curious as to what these lines do once they hit...
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