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. B

    Physics Test Question, Electromagnetism (induced charges) (grade 12)

    Homework Statement Right hand rule to determine Homework Equations There is no equation The Attempt at a Solution At point 1 and 5 there is no induced current, at point 2 and 4 there is a induced current.
  2. C

    Why Does SQRT(3) Factor into the Coulomb Force in an Equilateral Triangle?

    Homework Statement 3 identically charged charges are placed at corners of an equilateral triangle of sides a. I need to find the force felt by each charge. To do this I have calculated the force from charges - "2 on 1" and then "3 on 1". The answer i get is (2*q^2)/4*Pi*e*a^2. This is not...
  3. M

    Electric Potential Between Two Charges

    Homework Statement I have a series of questions regarding electric potential at various points in space given various point charges. The one that would probably be best to focus on is a charge of +q and a second charge of -2q a distance "d" further along the x-axis, find the non-infinity...
  4. T

    Equation of Continuity of charge for point charges

    Homework Statement I am looking to demonstrate that the expressions for the charge and current density of point charges satisfy the equation of continuity of charge. Intuitively it makes sense to me but I run into trouble with the delta function when I try to prove it mathematically.Homework...
  5. F

    Potential Energy of a pair of charges question

    Homework Statement Two point charges of magnitude 4.79 nC and −1.11 nC are separated by 39.4 cm. The acceleration of gravity is 9.8 m/s^2 The Coulomb constant is 8.98755×10^9 N · m^2 /C^2. What is the potential energy of the pair of charges? Answer in units of V. Homework Equations...
  6. F

    Physics Case: Electric Charges and Forces.

    Homework Statement Four punctual charges are located as shown in the figure below. A, B, and C are located at the vertices of an equilateral triangle. The values for these charges are A = +1.4microculombs, B = 4.5microculombs, C = -6.7microculombs and D = +7.1microculboms. THe length of the...
  7. L

    Bringing 3 Charges from infinity into a triangle

    Homework Statement How much work is needed to arrange three charges, Q, into an equilateral triangle? The particles are initially infinitely far apart. Take 'a' to be the length of each side of the triangle. Homework Equations U = {(kqq)/L} The Attempt at a Solution I was under...
  8. W

    3 Point charges on an x-axis

    Two point charges are located on the x axis: one charge q_1 = -15.0nC located at x_1 = -1.745m , and a second charge q_2 = 38.5nC at the origin.What is the total force along the x axis, including sign, exerted by these two charges on a third charge q_3 = 47.0nC placed between q_1 and q_2 at x_3...
  9. A

    Electric field when there are 3 charges

    Homework Statement A point charge q = +2.8 µC is placed at each corner of an equilateral triangle with sides 0.19 m in length. (a) What is the magnitude of the electric field at the midpoint of any of the three sides of the triangle? Homework Equations E=kq/r^2 k=9e9 all q's are...
  10. T

    An estate agent charges 0.75% fees .

    An estate agent charges 0.75% fees... Homework Statement An estate agent charges 0.75% fees on the sale price of a house. 1. Find his fees if a house is sold for €450,000 and VAT @ 20% is added on. 2. Find the selling price of a house if the fees are €2775 before VAT is added Homework...
  11. A

    Flow of charges in a conductor

    in the case of a spherical conductor the charges reside on the surface...the electric field is perpendicular to this surface (radial) and no parallel component exists ,as it leads to the flow of charges across the surface...why is this flow not feasible i.e why does the parallel component...
  12. B

    Calculating Forces on Two Charges Above a Conducting Sheet

    Homework Statement Two charges +Q and -Q are a horizontal distance a apart and a vertical distance b above a large conducting sheet. Find the components of the forces acting on each charge. Homework Equations The Attempt at a Solution Ok well I've tried to solve this using image...
  13. P

    RC Circuit: charges on two capacitors

    Homework Statement At t=0m the switch is open and both capacitors are uncharged. What are the charges on each plate (magnitude and sign) of each capacitor long after the switch is closed and capacitors are fully charged? Homework Equations q=C E(1-e^(-t/RC) The Attempt at a Solution...
  14. N

    Three charges in a plane- static and current electricity

    Homework Statement An equilateral triangle has sides of 0.11 m. Charges of -8.6, +8.0, and +1.5 µC are located at the corners of the triangle. Find the magnitude of the net electrostatic force exerted on the 1.5-µC charge. Homework Equations kqQ/d^2 The Attempt at a Solution first...
  15. W

    Resultant Force on -2x10^-6 C Point Charge Near 3 & -4x10^-6 C

    Homework Statement Determine the resultant force acting on a point charge of -2 x 10 ^-6 C situated at the origin of a rectangular coordinate system in the vicinity of point charges 3x10^-6 C and -4x10^-6 C at distances 0.12 m along the positive x-axis and 0.08m along the half-line x=y...
  16. K

    V Due To Infinite Line of Point Charges

    1. Homework Statement An infinite number of point positive charges of 2.0 C each are arranged in the following linear configuration with a = 88 cm. Find the electric potential at the point 0 on the scale. (link to image) http://img232.imageshack.us/i/prob02.gif/ 2. Homework...
  17. K

    V Due To Infinite Line of Point Charges

    Homework Statement An infinite number of point positive charges of 2.0 C each are arranged in the following linear configuration with a = 88 cm. Find the electric potential at the point 0 on the scale. (link to image) http://img232.imageshack.us/i/prob02.gif/...
  18. E

    Velocity in relation to Electric charges.

    Homework Statement From a large distance away, a particle of mass m1 and positive charge q1 is fired at speed v in the positive x direction straight toward a second particle, originally stationary but free to move, with mass m2 and positive charge q2. Both particles are constrained to move...
  19. A

    Work with Charges and Electric Potential

    Homework Statement How much work is required to assemble eight identical point charges, each of magnitude q, at the corners of a cube of side s? Note: Assume a reference level of potential V = 0 at r = infinity. (Use any variable or symbol stated above along with the following as necessary...
  20. S

    Calculate Speed of a Charged Particle in a Square

    Homework Statement IP One of the - charges in the figure (sqaure, with one charge at each corner) is given an outward "kick" that sends it off with an initial speed while the other three charges are held at rest. If the moving charge has a mass , what is its speed when it is infinitely far...
  21. A

    Are Noether charges a rep of the generators on the Hilbert space

    I'm trying to understand the relationship between conserved charges and how operators transform. I know that we can find conserved charges from Noether's theorem. If (for internal symmetries) I call them Q^a = \int d^3x \frac{\partial L}{\partial \partial_0 \phi_i} \Delta \phi_i^a then is it...
  22. S

    Finding distance of approaching charges

    Two large parallel copper plates are .05 meters apart and have a uniform electric field between them. An electron is released from the negative plate at the same time that a proton is released fro the positive plate. Neglect the force of the particles on each other and find their distance from...
  23. B

    Explaining Electric Flux with Enclosed Charges

    I under stand that electric flux is proportional to the charged enclosed but I don't get why. Homework Statement Consider the sphere with the charged enclosed: [PLAIN]http://electron9.phys.utk.edu/phys136d/modules/m4/images/Image985a.gif As you can see the area and electric field...
  24. T

    Electric Forces between three charges

    An electron is near a positive ion of charge +9e and a negative ion of charge −8e (see the figure below). (Take a = 5.23 µm, b = 4.28 µm, and θ = 54.9°.) (a) Find the magnitude and direction of the resultant force on the electron. (Let right be the +x-direction. Measure the angle...
  25. T

    Electric Forces between charges

    [b]1. Hanging from threads are two charged balls made of pith (a very light, spongy material that comes from inside the stems of certain plants). The balls each have a mass of 0.100 g and a charge of the same magnitude q and are attracted toward each other, as shown in the figure below...
  26. T

    Calculating Forces and Acceleration Between Charged Particles

    An electron is near a positive ion of charge +9e and a negative ion of charge −8e (see the figure below). (Take a = 5.23 µm, b = 4.28 µm, and θ = 54.9°.) (a) Find the magnitude and direction of the resultant force on the electron. (Let right be the +x-direction. Measure the angle...
  27. D

    TWO Point Charges on the x-axis and an electric field graph

    Homework Statement Two point charges qA and qB are located on the x-axis at x=a and x=b. The figure is a graph of Ex, the x-component of the electric field. What are the signs of qA and qB? Homework Equations http://session.masteringphysics.com/problemAsset/1071455/4/29.EX31.jpg...
  28. L

    Electric Potential of Two Positive Charges at Point A on y-Axis

    https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/phys2112/spring/homework/Ch-24-E-Potential/2_pt_chrgs/set3p02.gif" 1. Homework Statement Two positive charges, each with Q = +11 µC, are fixed to the x-axis at x = +a and x = -a, where a = 2 m. (a) Find the electric...
  29. F

    What are they doing? Charges and Conductors

    Homework Statement http://img823.imageshack.us/img823/236/40553004.png [PLAIN][PLAIN]http://img717.imageshack.us/img717/1561/15355872.png The Attempt at a Solution I am a bit confused isn't the 6.00nC sending its own E-field? For part b) Why do they say Qinside is 0...
  30. J

    Calculating Image Line Charges for Multiple Wires

    I have the below figure I took from my textbook from a section that explains how to calculate the capacitance of two transmission wires using image line charges. My question is that if I add two more conductors like shown below, how would it affect the line image charges? I'm not sure...
  31. A

    What is the electric potentional for these charges?

    Homework Statement Find the electric potential energy for the following array of charges: charge q1 = +4.0 µC is located at (x, y) = (0.0, 0.0) m; charge q2 = +3.0 µC is located at (4.0, 3.0) m; and charge q3 = −1.0 µC is located at (0.0, 3.0) m. _____ mJ Homework Equations...
  32. P

    What Happens when 2 Unlike Charges Approach Each Other Closely?

    Hi everyone, I was wondering if 2 unlike charges are placed a certain distance d apart, they will attract and move towards each other and the attractive force is given by Coulomb's kq1q2/r^2. Since r cannot be equals to zero as it would imply that the 2 charges exist as the same point in...
  33. R

    Bare Charges of Identical Particles: Is It Possible?

    For two particles which have identical physical charges (say under electromagnetism), are the bare charges necessarily the same? Since the physical charge is related to the bare charge by photon and particle renormalization factors, I don't see how this could be the case in general. In some...
  34. S

    Field and force with three charges

    Homework Statement At a particular moment, three small charged balls, one negative and two positive,are located as shown in the figure. q1 = 3 nC, q2 = 7 nC, and q3 = -5 nC. What is the electric field at the location of Q1, due to Q2? y q1 | | | q2______q3____x Okay...
  35. T

    Equilibrium question about charges.

    Which of the following are true? "Equilibrium" means that no charges are flowing. A. The net electric field inside a block of aluminum is zero under all circumstances. B. The electric field from an external charge cannot penetrate to the center of a block of iron. C. In equilibrium...
  36. B

    How Do You Calculate Unknown Charges in an Electric Field Problem?

    Homework Statement There are two opposite charges of equal magnetude, Q1 and Q2 separated by 4m. There is a central segment of 0.1m AB located centrally between the two charges AB. The electric field between AB can be taken as uniform. An electron is released with negligable speed at A and...
  37. A

    Electric field due to point charges and a ring of charge:

    Homework Statement A ring of charge with radius R = 0.5 m is centered on the origin in the x-y plane. A positive point charge is located at the following coordinates: x = 19.0 m y = -14.6 m z = -2.6 m The point charge and the total charge on the ring are the same, Q = +40 C...
  38. A

    Force problem What is the electric force on q3 due to the other 2 charges?

    Homework Statement Three point charges are fixed in place in the right triangle shown below, in which q1 = 0.71 µC and q2 = -0.67 µC. What is the electric force on the +1.0-µC (let's call this q3) charge due to the other two charges? image: http://www.webassign.net/grr/p16-15alt.gif...
  39. D

    Two unequal charges repel, suspended from same point.

    1. Two small, identical spheres of mass m each are attached to thin light threads of length L each and hung from the same point. When charges q1 and q2 are placed on upon the spheres(with both charges having the same sign), the two spheres repel each other and, upon reaching equilibrium, hang at...
  40. C

    Two fixed charges and one free to move problem.

    Homework Statement Three charges, Q1, Q2, and Q3 are located in a straight line. The position of Q2 is 0.301 m to the right of Q1. Q1= 1.39x10-6 C and Q2= -3.22 x10-6 C are fixed at their positions, distance 0.301 m apart, and the charge Q3= 3.33 x10-6 C is moved along the straight line. For...
  41. M

    Point charges in a electric field

    Homework Statement Two large parallel copper plates are 5.0cm apart and have a uniform electric field between them. An electron is released from the negative plate at the same time that a proton is released is released from the positive plate. neglect the force the particles have on each other...
  42. Z

    Calculating Electric Field of Two Point Charges

    Homework Statement A point charge of -7e-6 C is located at x = 3 m, y = -2 m. A second point charge of 12e-6 C is located at x = 1 m, y = 3 m. Homework Equations The Attempt at a Solution Dq1 = sqrt(20) Dq2 = sqrt (13) E1 + E2= k(-7e-6)/20 + k(-7e-6)/20 = 11444.96 N/C...
  43. P

    Leaky capacitor and movement of charges

    Assume that we have a parallel plate capacitor filled with an imperfect dielectric. Then we apply a DC Voltage between the plates and expect some leakage current through the capacitor due to the dielectric having non-zero conductivity. My question regards the movement of electric charges...
  44. C

    Finding the net force on a charge in the center of 4 other charges.

    Homework Statement Four charges Aq,Bq,Cq, and Dq (q = 5.00 × 10-7C) sit in a plane at the corners of a square whose sides have length d = 83.0 cm, as shown in the diagram below. A charge, Eq, is placed at the origin at the center of the square. DATA: A = 2, B = 4, C = 7, D = 4, E = -5...
  45. M

    Calculating Electric Field in a Square of Charges

    Homework Statement A square with sides d has charges q, 2q, 3q and 4q arranged clockwise around the corners of the square. What are the magnitude and direction of the field at the centre of the square? Hints: consider pairs on opposite sides of the square. Choose a coordinate system that makes...
  46. G

    Equipotential lines for two charges

    Hi there, Could you describe for me what happens to the equipotential lines of two charges as they move close to each other. Thanks
  47. jegues

    Point of Equilibrium between two charges

    Homework Statement See figure attached for problem statement. Homework Equations The Attempt at a Solution I'm a little confused on how to start on this one. Okay so I know that the two particles with oppsite charge attract one another, and a 3q force of attraction is going...
  48. F

    Like charges repel and unlike charges

    Homework Statement Unlike charges attract. Now here is my question, is this a phenomenon of Newton's third Law? I couldn't ask my lecturer because I had to run to another class for a quiz. It's friday and I don't want to ruin his friday. The "repelling" force is a real right?
  49. L

    Charges placed on a hexogon, working out the force and energy

    Six equal charges, each Q coulombs, are placed at the vertices of a regular hexagon of side a, as shown above. What is the net force acting on the charge at D as a result of the other 5 charges? [3] d) Calculate the total electrostatic energy of the system of 6 charges in (c) Its only work...
  50. I

    The placing of charges in electrostatics

    Homework Statement Two point charges, one with charge +q and the other with charge +9q, are placed a distance "d" apart. It is possible to place a third charge so that the net electrostatic force on all three charges is zero. What are the sign, magnitude, and position of this third charge (in...
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