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. R

    Net Electric Field Between Two Point Charges

    Homework Statement Two point charges q1 = 4.90×10-5 C and q2 = 2.45×10-4 C are separated by a distance d = 0.10 m. Compute their net electric field E (x) as a function of x for the following positive and negative values of x, taking E to be positive when the vector E points to the right and...
  2. R

    Two charges, Electrical Potential

    Homework Statement Two charges q = 9.0μ C are fixed in space a distance d = 1.5 cm apart, as shown in the figure. a) With V = 0 at infinity, what is the electric potential at point C? b) You bring a third charge q = 9.0μC from infinity to C. How much work must you do? c) What is the...
  3. Y

    Three charges located on a straight line

    Homework Statement Three charges, Q1, Q2 and Q3 are located on a straight line. The charge Q3 is located 0.169 m to the right of Q2. The charges Q1 = 1.56 μC and Q2 = -3.03 μC are fixed at their positions, distance 0.268 m apart, and the charge Q3 = 3.18 μC could be moved along the line. For...
  4. julianwitkowski

    Coulomb's Law, Charges and Acceleration

    Homework Statement An electron is fired at 4.0 e+6 m/s horizontally between the parallel plates as shown, starting at the negative plate. The electron deflects downwards and strikes the bottom plate. The magnitude of the electric field between the plates is 4.0 e+2 N/C. The separation of the...
  5. R

    Electric Field at Center of Square: Mag & Dir

    Homework Statement In the figure, four charges, given in multiples of 5.00×10-6 C form the corners of a square and four more charges lie at the midpoints of the sides of the square. The distance between adjacent charges on the perimeter of the square is d = 1.30×10-2 m. What are the magnitude...
  6. G

    Electric potential of a cube of 8 point charges

    Homework Statement Find the Electrostatic potential energy of a cubical configuration of point charges. (One charge on each corner of a cube). Each of the charges is 3.00e and the edge of the cube is 3 cm. Homework Equations U = kqQ/r The Attempt at a Solution I'm pretty sure I understand...
  7. O

    Two indentical beads w/ mass m and charge q in hemispherical

    Homework Statement Two identical beads each have a mass m and charge q. When placed in a hemispherical bowl of radius R with frictionless, nonconducting walls, the beads move, and at equilibrium, they are a distance d apart (see figure below). Determine the charge q on each bead. Homework...
  8. Panda_Doll

    Three Charges in a Triangle problem

    Homework Statement [/B] Three 3.0 g balls are tied to 80-cm-long threads and hung from a single fixed point. Each of the balls is given the same charge q. At equilibrium, the three balls form an equilateral triangle in a horizontal plane with 20 cm sides. Homework Equations F=kq1q2/r^2 F (of...
  9. G

    How does a magnetic field "push" charges?

    I was under the assumption that a magnetic field acts similar to that of the normal force in mechanics; both affect the path of the object, but do no work. So now suppose that we have a rectangular circuit with the left side in an uniform magnetic field that is pointing towards the computer...
  10. Samurai44

    How Do You Locate the Neutral Point Between Multiple Charges on a Line?

    Hello , If i was given two or three charges separated , and they all lie on the same straight line ... how can I identify the neutral point ? * Take any value for their separation , their charges and sign if you want to give an example ,, just a general question
  11. R

    Three Point Charges, Find x-component

    Homework Statement In the figure, three point charges are arranged in a equilateral triangle of side a= 1.40×10-2 m. Sketch the field lines due to + Q and -Q, where Q = 2.50×10-5 C , and from them determine the direction of the force that acts on +q = 5.00×10-8 C because of the presence of the...
  12. R

    Find Net Electric Field Between Two Point Charges

    Homework Statement In the figure, two point charges q1 = 3.40×10-5 C and q2 = 1.70×10-4 C are separated by a distance d = 0.10 m. Compute their net electric field E (x) as a function of x for the following positive and negative values of x, taking E to be positive when the vector E points to...
  13. 1

    First post, Electrostatics Questions

    Homework Statement Options for answers: positive, negative, neutral, cannot tell 1) a positive point charge is brought near the outside surface of a neutral conducting sphere and released. The initial position of the point charge is on the on the positive x-axis and the sphere is centered on...
  14. J

    Charges near a conducting plane

    Homework Statement Locate two charges q each and two charges –q each on the corners of a square, with like charges diagonally opposite on another. Show that there are two equipotential surfaces that are planes. In this way obtain, and sketch qualitatively, the field of a single point charge...
  15. T

    Two charges and electric field?

    Homework Statement Two charged particles are located on the x axis. The first is a charge +Q at x= -a. The second is an unknown charge located at x= +3a. The net electric field these charges produce at the origin has a magnitude of 2kQ/a^2. Explain how many values are possible for the unknown...
  16. Raiden60

    Atom Charge Swap: Can It Be Possible?

    I was thinking what would happen if an atoms charges swap places. Not like, the proton switching places with the neutron, their mass would be unchanged, but their charge would be different. Could this be possible?
  17. R

    Is a Grounded Plane Electrically Neutral?

    Consider the following configuration: a grounded plane (very thin and with an infinite surface) and a positive (not important) point charge above it. What does grounded really mean? Can't I assume that it is neutral and it has infinitely many positive and negative charges? Because of the...
  18. Samurai44

    Neutral Point between point charges

    Homework Statement How can I find the nuetral point between two charges or more ? Example:[/B] (-Q3)...(0.8m)......(Q2)...(0.3m)...(P)...(0.3m)...(Q1) Q1=2nC ,,, Q2=3nC,,, Q3=-4C ,,, q: Determine in which direction must be Q3 moved to make P neutral? Calculate the distance which P will be...
  19. Y

    Magnetic field could only affect moving charges?

    no other thing is under effect of B ? srry .i m not good in eng , hope u seniors can understd my q. thanks lot..
  20. kmm

    Work Done on a System of Charges

    Something I have read in Griffith's Electrodynamics is confusing me. In deriving the Poynting vector, he says to suppose that we have some charge and a current configuration which at some time t produces fields E and B. In the next instant, dt, the charges move around. He then asks the question...
  21. genxium

    Is it able to make point charges stationary by electric force?

    First by "stationary" I mean "with respect to each other" so as to avoid introducing relativity problems. I'm wondering whether there's a way to prove or disprove that given N > 1 point charges q_1, q_2, ..., q_n, is there always a way of putting them in 3-dimensional space such that all of...
  22. I

    Experiment: my like charges didn't repel

    i had a battery powered device that outputted 5kV DC . i hooked up one of the output leads to two long pieces of Al foil. i was expecting a repulsion but nothing happened, why? is the voltage not high enough?
  23. K

    Electron moving between 2 point charges

    Homework Statement A point charge $$q_1=+20\cdot 10^{-9}[Coulomb]$$ is 5[cm] distance from charge $$q_2=-12\cdot 10^{-9}[Coulomb]$$. An electron is released from 1[cm] distance from q2. what is it's velocity 1[cm] from q1. Homework Equations The potential=Voltage from a point charge...
  24. K

    Electric charges at the corners of a square

    Homework Statement 3 point charges, q1=+2E-9[Coulomb] are placed at the corners of a square of 0.2[m] edge. what is the potential at the center. Homework Equations The potential of a point charge at distance r: $$V[Volt]=K\frac{q}{r}$$ ##K=\frac{1}{4\pi\varepsilon_0}=9\times 10^9## The...
  25. AdityaDev

    Redistribution of charges in capacitor

    Homework Statement A capacitor of capacity C is charged with potential difference V. Another capacitor of capacity 2C is charged to 4V.they are connected with reverse polarity after removing batteries. The heat produced during redistribution of charges is... Homework Equations ##Q = CV## ##U...
  26. Y

    Using Method of Imaging for two point charges between Parallel Plate Capacitors

    Homework Statement Use either image charge method of separation of variables to solve: The distance between two large, grounded parallel conducting plates is 4x. Between them, two point charges +Q and -Q are inserted and have a distance x and 3x from one of the plates. (A line connecting the...
  27. Y

    Solution to Image Charge Method for Two Point Charges

    Homework Statement Two point charges of equal value are placed a distance 2b from one another. In the middle, there is a grounded conducting sphere. What is the minimum radius of the sphere required to cancel out the repelling force between the two charges? (Solve using Image Charge Method)...
  28. diegzumillo

    Inverse of method of image charges

    Hi all What if instead of charges and a surface, we were given a set of charges and image charges and have to find the surface, how would you do that? This is actually part of my homework but I'm pretty sure he doesn't want us to prove it mathematically (the case is obviously a sphere) so I...
  29. Hijaz Aslam

    Electric Field of a circular arc at a point

    Homework Statement Given that the circular arc wire with radius 'r' has a linear charge density ##\lambda##. What is the Electric field at the origin? Homework Equations ##\vec{E}=\frac{kq}{r^2}## where ##k=9\times10^9## is a constant. 3. The Attempt at a Solution I took a small segment dy...
  30. C

    Electric Field due to Point Charges

    Homework Statement [/B] The following is on a practice exam I have been completing. In advance, it is part b I am struggling with. Two point charges Q1 = +5*10^(-6)C and -2*10^(-6)C are 50cm apart. a) Where along a line that passes through the two charges is the electric potential zero (apart...
  31. C

    Electric Potential- Two Charges

    Homework Statement Two identical particles, each with a mass of 2.0 mg and a charge of 25 nC, are releasedsimultaneously from rest when the two are 4.0 cm apart. What is the speed of either particle at the instant when the two are separated by 10 cm? Homework Equations PE=ke*q1q2/r The...
  32. D

    Potential difference due to two uniform sheet charges

    Homework Statement a) Derive the expression for the potential difference due to two uniform infinite sheet charges at y=5 and y=-5 in free space. b) If V=4V at (0,2,10) find V at (-4,3,1) . The surface charge density on the two sheet charges are ?s=?0 col/m2 [/B]Homework EquationsThe Attempt...
  33. D

    Potential difference due to two uniform infinite sheet charges

    a) Derive the expression for the potential difference due to two uniform infinite sheet charges at y=5 and y=-5 in free space. b) If V=4V at (0,2,10) find V at (-4,3,1) . The surface charge density on the two sheet charges are ?s=?0 col/m2 What you guys be able to help me with this ?
  34. N

    A rectangle with Charges on Each Corner - Find Missing Charge?

    Homework Statement A charge is to be placed at the empty corner of a rectangle to make the net force at corner A point along the vertical direction. What charge (magnitude and algebraic sign) must be placed at the empty corner if the three charges have the same charge of +8.45 μC?Homework...
  35. N

    Field due to point charges - extremely strange error

    Homework Statement Find electric field anywhere on the x-axis due two two point charges Q at (0,0,d) -Q at (0,0,-d) Homework EquationsThe Attempt at a Solution AttachedSomehow I am not getting the correct answer. I reviewed my steps with 4 people and we could not find the error! I'm...
  36. M

    Work needed to move opposite charges farther apart

    Homework Statement Suppose you want to move two charges apart, both are equal charges of opposite sign at 1.4x10^9C, and their starting position is 6.7m apart, how much work would it take to further separate the charges to a final distance of 7.9m, that is, move them 1.2m Homework Equations...
  37. B

    Equilibrium position of a charge between other 2 charges

    Homework Statement Place a third charge q between two charges Q1 = -2Q and Q2= 3Q so they stay in electrostatic equilibrium. Knowing that the distance between Q1 and Q2 is equal L Homework Equations (KQ1Q)/(QQ1)2 = (KQ2Q)/(QQ2)2 3. The Attempt at a Solution Let's start by saying that i know...
  38. M

    Voltage between two point charges

    HI, Would the voltage change between two point charges say + and - as you increase the distance between them? When you have two charge parallel plate capacitors, that was charged but a battery then disconnected, its a different story right? The voltage increases? Thanks
  39. J

    Finding the Electric Field as a Result of Two Point Charges

    Homework Statement There is a −3 µC point charge at (0,0,4) and a +3 µC point charge at (0,0,-4). What is the magnitude and direction of the electric field at point (0,0,8)? What is the magnitude and direction of the electric field at point (0,0,8)? [/B] Homework Equations E = \frac{ k_e q...
  40. USeptim

    Power radiated by several charges and the Larmor Formula

    Hello, The Larmor Formula tells how much power radiates a particle under the effect of acceleration if it's lonely on the space and it's often used to calculate radiative losses. However, I have seen some situations where the total radiated power cannot be obtained as the sum of Larmor formula...
  41. J

    A question about moving electric charges and their force

    I want to find out whether I'm doing something wrong, and where to look for similar thinking. Imagine a thin wire that carries a constant electric current. Negative charges move to the right. Positive charges are stationary. The charges balance on average, or maybe there are a few more negative...
  42. Joa Boaz

    Two positive point charges q1 and q2 are separated by a distance d.

    Two positive charges Q1 and Q2 are separated by a distance d. Find a general expression for the distance from Q1 at which the electric field is 0 by defining Q2 as alphaQ1 (alpha > 0 with alpha not equal to 1). This expression should contain alpha, d, and possible some numeric constants. Check...
  43. F

    Magnetic poles and their charges

    What is the reason for the analogy that a magnetic south pole can be considered negative and a magnetic north pole positive? I understand magnetic field lines run from North to South and electric field lines run from positive to negative. Is this the only basis? Or are the magnetic poles...
  44. A

    Coulomb's Law and point charges

    Two m = 6.0g point charges on 1.0-m-long threads repel each other after being charged to q = 120nC , as shown in the figure. What is the angle θ? You can assume that θ is a small angle. Hopefully the image will work. I feel like something is missing. I've gotten 7.4 and 3.4 degrees...
  45. Rectifier

    Two charges touching each other

    Hey! This isn't a question from a book. Its something that I am not 100% sure about. The question What happens if two iron balls with charge Q each, touch each other? My thought These balls can be seen as a separate ball with a charge of 2Q. ( I am not so sure what to say about the volume of...
  46. davidbenari

    Potential energy stored in a system of point charges

    The basic equation is as follows: U=∑kqiqj/Rj with (i≠j) My question is how is this definition useful? What makes you want to say that is the potential energy of the system? For example, I thought that it is useful because if all particles change in position then you could evaluate that...
  47. P

    Electric field strength from two charges

    Homework Statement Two identical point charges, q1 = +2.5 x 10-6 C and q2 = +2.5 x 10-6 C, are placed as shown in the diagram below. Point P is a distance 0.05 m from q1 and 0.12 m from q2, such that the angle at P is 90 degrees. Calculate the magnitude of the Electric field E at point P...
  48. Rectifier

    What Value Should Charge C Have to Nullify the Net Force on Charge B?

    1. The problem There are four charges hat are placed in a rectangle-like pattern. Three of them are equal (A, B, D). What charge should C be so that the net force at charge B is zero? 2. Relevant information (No distances are given) 3. The attempt First of all, I did this image to visualize...
  49. I

    Why do opposite charges attract and like charges repel?

    Why does the electric force vectors around a positive charge point outwards and the electric force vectors around a negative charge point inwards?
  50. D

    Find Min Force on Particle 3 with q1,q2,q3 Charges

    Homework Statement Particles 1 and 2 are fixed in place on an x-axis at a separation of L=8cm. Their charges are q1=e q2=-27e. Particle 3 with charge q3=4e is to be placed on the line between particles 1 and 2, so that they produce a net electrostatic force F3net on it. a) at what...
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