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.

View More On Wikipedia.org
  1. X

    Electrostatic Force between point charges

    Homework Statement The attractive electrostatic force between the point charges 8.12×10−6C and Q has a magnitude of 0.670N when the separation between the charges is 7.26m. Find the sign and magnitude of the charge Q. (this is a direct cut and paste) Homework Equations...
  2. M

    Charges on a square - find forces

    Homework Statement A charge of 6 mC is placed at each corner of a square .1 m on each side. Determine the magnitude and driection of the force. Homework Equations The Attempt at a Solution so i found the force between corner 1 and 2 then 1 and 3 to = 32.4N and the force...
  3. C

    Electrical Charges and Attraction

    Hi, Pls I'd like to find out if 2 electrical charges (same charge but different voltages) would attract or repel. For example -600VDC and -100VDC. I've always thought like charges repel and unlike charges attract. But I'm reading up on something that says the above would attract and become...
  4. D

    Heat Generation in a circuit due to moving charges

    1. Homework Statement A capacitor of capacitance C id charged by a battery of emf E and inernal resistance r, A resistance 2r is also connected in series with the capacitor. The amount of heat liberated inside the battery by the time capacitor is 50% charged is? Answer is E2/C 2...
  5. I

    Neutralizing Forces Between Electric Charges

    Homework Statement Consider a charge of +2.0 µC placed at the origin of an X-Y co-ordinate system and a charge of -4.0 µC placed 40.0 cm to the right. Where must a third charge be placed – between the charges, to the left of the origin, or beyond the second charge – to experience a net force of...
  6. R

    Help with deriving an equation (coloumb's law, pith ball charges)

    Homework Statement A lab we were recently given in AP Physics class contained an equation already derived. This lab was about determining the charge on a pith ball, using the static charge of a fur to charge the balls negatively, so they repel. Finding the angle and distance between the two...
  7. L

    Charges without fields, fields without charges

    Hello, As many people, I have been fascinated by the "Classical electrodynamics in terms of direct interparticle interaction" theory developped by Feynman and that he abandonned later. This is a representation of electrodynamics where fields play no direct role: they do no appear in the least...
  8. C

    Exploring Electric Fields: Test Charges & Magnetic Fields

    1. Homework Statement Here is the picture with the arrows representing Electric Fields. a. Can you find any test charges on the xy plane? Where? b. Where can you find a magnetic field? 2. Homework Equations No idea... Amperes Law? 3. The Attempt at a Solution I just...
  9. W

    Coulomb Force Point Charges on Cube

    Hello, I'm having a little trouble with this: Coulomb Force Point Charges on Cube Homework Statement Identical charges of Q (C) are located at the eight corners of a cube with side L (m). Show that the coulomb force on each charge has magnitude: 3.29Q^2/4\pi\epsilon_0l^2 Homework Equations...
  10. D

    Magnetization in Classical EM: Bound Electric vs. Magnetic Charges

    I have been trying to remember if in classical EM it is equivalent to describe magnetization through bound electric currents A. \vec{j_b} = \nabla \times \vec M \vec{k_b} = \vec M \times \vec{\hat{n}} OR bound magnetic charges B. \rho_b = -\nabla \cdot \vec M \sigma_b = \vec M \cdot...
  11. 6

    Potential at a point due to two charges

    I've been working on this problem and I cannot find out where I am making a mistake. Homework Statement Two charges, each with a value of +q, are placed a distance d apart on the x-axis. Find the potential at a point P a distance z above the x-axis on the z-axis The Attempt at a Solution The...
  12. A

    Coulombs Law & Electric Charges

    Homework Statement Two negative electric charges, (Charge A on the left, and Charge B on the right) each with a charge of 3.0 x 10-5 Coulombs are fixed at a distance of 2.9 meters from each other. Find the electric force of charge A on charge B. (Don't forget, if the force points to the left...
  13. E

    How do I calculate the ratio of charges for metal sphere?

    Homework Statement here's how the question goes: the magnitudes of the charges on two identical small metal spheres are in the ratio 5:1. the coulomb interaction force between them is F1. if they are brought into contact and then separated to their respective original positions, the coulomb...
  14. B

    Calculating Electric Field and Flux Density - Point Charges Homework Solution

    Homework Statement Point charges of 12x10-6, -7x10-6 and 4x10-6 are located at (2,0,-1), (1,1,2) and (2,-1,2). a. Determine D(flux density) and E(electric field strength) at (1, -1, 3). b. What is the flux passing through the sphere of radius of 2.5 centered on the origin Homework...
  15. D

    Electric field of point charges

    Homework Statement A 4microC point charge is placed at the coordinate origin. Two other point charges are placed on the x axis: q1 at x=30cm and q2 at x=50cm. Find the magnitude and sign of q1 and q2 if the net force on each of the three charges is zero. Homework Equations...
  16. D

    Electric Fields - Net Charge on Point Charges

    Homework Statement Two point charges are placed on the x axis: +5 microC charge at x=0 and +8 microC charge at x=0.9m. Where on the x-axis can a third charge be placed so that the net charge on all three charges is zero? Determine the magnitude of the third charge. Homework Equations...
  17. B

    Physics - Determine Pith Ball Charges

    Homework Statement Two pith balls equally charged and each with mass of 1.5g. While one ball is suspended by a thread, the other is brought close to it and a state of equilibrium is reached. In that situation, the two balls are separated by 2.6cm and the thread is attached to the suspended...
  18. J

    How the charges are transferred?

    "When we touch a pith ball with an electrified plastic rod, some of the negative charges on the rod are transferred to the pith ball and it also gets charged." I want to know how does this happen ?
  19. T

    Two line charges and a conducting cylinder are flying through space

    Homework Statement Griffiths 3.36: Two straight wires having equal and opposite line charges are situated on either side of a conducting cylinder (all the wires and the cylinder are "long", so we can ignore edge effects--this is undergraduate electrostatics, after all!). The cylinder has no...
  20. M

    Electron and Proton Charges: A Fundamental Mystery or a Natural Phenomenon?

    The charge of an electron is exactly equal in magnitude to that of a proton (2 up quarks plus down quark). What is the theoretical basis for this, or is essentially a fact of nature that is accepted?
  21. E

    Why Static Charges are Affected on Dry Days

    Homework Statement why should experiemnts related to static charges be carried out on dry days? Homework Equations I know this somehow relates to the moisture in air. yet, I do not understand the concept behind. The Attempt at a Solution Do the sparks...
  22. X

    Two charges, individual charge values?

    1. Two point charges 3.0 cm apart have an electric potential energy -120 microJoules. The total charge is 30 nC. What is the lesser charge? What is the larger charge? 2. Uele=qv Uele=q1(kq/d) 3. My professor gave me these equations, I'm not entirely sure if they're the right ones...
  23. M

    Charge distribution of two plates with different charges?

    If there are two plates with +2Q and -Q, what is the charge distribution on the four faces? I would assert this is the only solution S1--------------------------- (+0.5Q) S2--------------------------- (+1.5Q) (space) S3--------------------------- (-1.5Q)...
  24. A

    Final distance between two charges, identical particles approaching each other

    Final distance between two charged, identical particles approaching each other Homework Statement Two identical particles, each with a mass of 4.5 mg and a charge of 30 nC, are moving directly toward each other with equal speeds of 4.0 m/s at an instant when the distance separating the two...
  25. B

    Electric potential of 3 point charges

    Homework Statement Three point charges, which initially are infinitely far apart, are placed at the corners of an equilateral triangle with sides "b". Two of the point charges are identical and have charge "q". If zero net work is required to place the three charges at the corners of the...
  26. M

    Electric Fields and charges of equal magnitude

    [b]1. Two point charges of equal magnitude are 8.4 cm apart. At the midpoint of the line connecting them, their combined electric field has a magnitude of 45 N/C. Find the magnitude of the charges. [b]2. E=k(q)/r^2 [b]3. I've tried 45= 8.99x10^9(q)/(.084)^2 and got q to equal 35...
  27. O

    Electric Potential Energy of A System of Point Charges

    A Particle of charge q=7.5x10^-6 Coulombs is released from rest at .6m on the x axis. The particle moves due to charge Q = -20x10-6 C. What is the Kinetic Energy of the particle the instant it has moved .4 meters if Q stays fixed at the origin? Here I used KE1 + U1 = KE2 + U2 Which equals 0 +...
  28. F

    Point charges and electric potential

    I have some difficulties grasping the idea of this equation Wp = q * E * r Where Wp - electrical potential energy q - charge E - the strength of the electric field r - radius, or distance from the other point charge So basically, say we have 2 point charges. One positive, and one...
  29. O

    In what direction does the sphere move between two positive charges

    Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/8fe997e1-46e5-4033-a246-fbad0acb7162 Homework Equations The Attempt at a Solution I understand that in question 25, the conductor becomes polarized and its negative charges will be more attracted...
  30. N

    Making a square with point charges (alternative solutions)

    Homework Statement Calculate how much work it takes to make a square of side length A with point charges (all of charge q) at each vertex. Homework Equations The Attempt at a Solution I know one way to do it. (find the difference in potential for each point and then go from there...
  31. M

    Find Potential Minimum of Two Point Charges

    Homework Statement A charge of 0.611 nC is placed at the origin. Another charge of 0.383 nC is placed at x1 = 8.1 cm on the x-axis. At which point on the x-axis does this potential have a minimum? Homework Equations U=(kq1q2)/rThe Attempt at a Solution I really have no idea how to even start...
  32. E

    Attraction between two charges in QED

    Attraction between nuclei and electron in QED is the most simply described with Feynman's diagram and calculation, when an electron fastly flow close to a nuclei. (?? scattering) 1. But how, in QED, to describe attraction between almost standstill electron and nuclei. In classical physics...
  33. V

    Electric field calculation for 3 point charges

    Hi I'm having difficulty understanding why the solution for the answer to the following problem is worked out this way. Three spheres are placed at fixed points along the x axis, whose positive direction points towards the right. Sphere A is at x=47cm with a charge of 5x10-6C Sphere B is...
  34. A

    Electric Force sphere charges

    A small sphere of mass 1.0 x 10^-6 kg carries a total charfe of 2.0 x 10^-8 C. The sphere hangs from a silk thread between two large parallel conducting plates. The excess charge on each plate is equal in magnitude, but opposite in sign. The thread makes an angle of 30 with the positive...
  35. somasimple

    Calculate Sum of Charges at Point A/B

    Homework Statement Attached figure. 3 charges : q1, q2 and q3 are on a plane (for simplification). We want to compute the resulting charge at some point of the plane. 1/ Is it possible to sum (for computation) these charges to an arbitrary point A? 2/ or B? Homework Equations these...
  36. G

    Electric Potential of 2 positive charges, and the speed

    QUESTION 1 Homework Statement Two positive charges, each with Q = +10 µC, are fixed to the x-axis at x = +a and x = -a, where a = 4 m. (a) Find the electric potential at point A on the y-axis where (xA, yA) = (0, b) and b = 5 m. Take the zero of potential to be at infinity. (b) A...
  37. D

    Electric force due to point charges

    Homework Statement 3 point charges are fixed in place in the right triangle shown below, in which q1= 0.67 microC and q2= -0.67 microC. What is the electric force on q3 with +1.0 microC due to the other two charges? Magnitude? direction, measured counterclockwise from the +x axis? **HYP=10cm...
  38. P

    How Does Varying Charge Affect Initial Acceleration of Point Charges?

    Q1. If two point charges have equal mass and and charg are released on a frictionless table, each has an initial acceleration (Ao). if instead you keep one fixed and release the other one, what will be its initial acceleration?Ao,2Ao or Ao/2? Q2. A point charge of mass (m) and charge (q)...
  39. E

    Calculating the magnitude of point charges

    Homework Statement A point charge of -6 µC is located at x = 1 m, y = -2 m. A second point charge of 12 µC is located at x = 1 m, y = 3 m. (a) Find the magnitude and direction of the electric field at x = -1 m, y = 0. (b) Calculate the magnitude and direction of the force on an...
  40. L

    Force on charges separated by grounded spherical condcutor

    Homework Statement Grounded conductive spherical shell is given. Radius R. Charge is held in d and (-d). d>R. as in the pic. What is the force on the right charge? Homework Equations F=q*q/r^2 The Attempt at a Solution I thought it's just F=(q^2)/(4d^2). Why it's wrong? the right...
  41. somasimple

    Moving Point Charges - Voltage Calculations

    Hi all, Here is my problem: Two positive points charges are situated as the initial figure: 1/ How to compute the voltage between A and B (or C)? 2/ If the final condition is like described in the second figure, what is now the voltage between A and B. 3/ if the transition between the...
  42. S

    What are the Tensions in a System of Fixed Point Charges?

    A fixed point charge of +2q is connected by strings to point charges of +q and +4q, as shown below. Find the tensions T1 and T2. (Use the following as necessary: q, d and k.) For T1, I summed all the forces on each charge and got...
  43. R

    Method of Image Charges - Range of validity of solutions

    When using the method of image charges to solve a problem in electrostatics, how do we determine the volume of space in which our solution is valid? And how do we find the solution outside this volume? To be more specific, let's consider two examples. The first is the classic point charge above...
  44. N

    Question about the electric field created by two charges?

    Two charges are located on the y-axis at positions -2 microC @ (0, 2m) and -1 microC (0,-2m). What are the x and y components of the electric field at position (2m,0)?
  45. P

    Consider the arrangement of two fixed point charges, equal in magnitude

    Consider the arrangement of two fixed point charges, equal in magnitude... Consider the arrangement of two fixed point charges, equal in magnitude, shown in the figure. Which of the following statements are correct for the initial motion of a third charge if it is released from rest in the...
  46. J

    Three charges and midpoint

    Homework Statement Three charges are at the corners of an equilateral triangle, as shown in the figure below. Calculate the electric field at a point midway between the two charges on the x-axis. Magnitude: Direction below the x-axis in degrees. Homework Equations F=Ke*q/(h)^2...
  47. J

    Point charges magnitude and direction

    Homework Statement Three point charges are located at the corners of an equilateral triangle as in the figure below. Find the magnitude and direction of the net electric force on the 0.40 µC charge. (A = 0.20 µC, B = 6.60 µC, and C = -3.80 µC.). Diagram below... Homework Equations F=...
  48. N

    I have a crime, but what kind of charges will suspect face?

    Scene in my book, in the United States. So some guy wants to maybe shoot someone, maybe just scare someone, whatever. But at some point the gun goes off and kills a bystander. Would this be involuntary homicide? Involuntary manslaughter? Any other charges a prosecutor might add? The...
  49. I

    How to merge an attractive force with one that has opposite charges and repulsion

    Hi, I saw this article on youtube about Brian Greene describing kaluza-klein and some ideas about tiny curved spatial dimensions: I was wondering...I'm looking for an intuitive (general idea without too much mathematics for starters) explanation as to how kaluza or string...
Back
Top