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

    Calculating the ratio of charges in Leyden Jar

    Hello In Walter Lewin's lecture while explaining the Leyden jar he says that the charge on the glass is 12 times more than that in the air gap. How is this obtained ? Basically there are 2 metal containers separated by a glass sheet. The air gap between the outer conductor and glass is 1...
  2. Q

    Identifying Charges Using a Pith-ball Electroscope?

    Question: Can you use a pith-ball electroscope, to determine the charge of an unknown object? Is it possible?
  3. K

    (Image Theory) Boundary conditions and how many image charges do i need?

    Homework Statement An electrostatic point charge of 1 Coulomb (C) placed symmetrically between two infinitely/perfectly conducting parallel plates. These two infinitely large conducting plates are parallel to the yz plane.The region between the two plates is designated as “Region A.” Starting...
  4. T

    Forces in a circle from similar charges?

    Hey guys, New here. It's been a while since I've done any physics. I've been playing around with some mental work in my head and I am trying to figure out why something doesn't work. I know it shouldn't work, but I can't figure out the why. What I am talking about is utilizing similar charges...
  5. M

    Energy of two charges in front of a plane

    Hello everybody and merry Christmas! Here is the text of the problem which has been puzzling me for the last few days: there are two charges distant d from one another and at distance a from a conducting plane. Find the electrostatic energy of the system. The first thing I find pretty strange...
  6. E

    Gauss's Law and Charges on Conductors

    A hollow conducting sphere has no net charge. There is a positive point charge at the center of the spherical cavity within the sphere. You connect a conducting wire from the outside of the sphere to ground. Will you measure an electric field outside the sphere? I know that since the electric...
  7. L

    Fast multipole method question. Point charges vs surface charges

    In many articles authors describe FMM for particles. e.g. http://www.csci.psu.edu/seminars/fallnotes/fmm.pdf http://www.umiacs.umd.edu/labs/cvl/pirl/vikas/publications/FMM_tutorial.pdf In other articles authors describe FMM for charged surface. How does these formulations relates? Main...
  8. Rasalhague

    Calculating Electric Field at (x,0,0) Due to Two Point Charges

    In lecture 2 of http://oyc.yale.edu/physics/physics/fundamentals-of-physics-ii/content/class-sessions , around the 50 minute mark, the professor calculates the value of an electric field at a point (x,0,0) on the x-axis of a cartesian coordinate system. (The video can be rather slow loading, so...
  9. B

    Charges of two capacitors in a circuit

    Homework Statement Capacitors C_1=6μF and C_2=2μF are first charged by connecting them in parallel across a 250V battery. The capacitors are then disconnected from the battery and connected positive plate to negative plate and negative plate to positive plate. Calculate their charges...
  10. R

    Determin the magnitude of the net electric field of three point charges

    Homework Statement There are three point charges, q1 has a magnitude of 3.00mC (the sign is not known) and is 5.0cm away from P and 13.0 cm away from q2. P is 12.0cm away from q2 and the three points form a triangle. The net electric field at point P is entirely in the negative y-direction...
  11. M

    Given two charges where to put thrid charge for zero net force

    Homework Statement Two charges, q1 and q2, are separated by a distance r. Find the position at which a third charge, q3, can be placed so that the net electrostatic force on it is zero. Homework Equations Coulomb's Law: F = (kq1q2)/r122 * (r12hat) The Attempt at a Solution I was...
  12. J

    Two Electric Charges- Electric Force-Ranking

    Homework Statement Below are seven arrangements of two electric charges. All of the charges are the same size, 20 C, but they are either positive or negative. Each figure also has a point labeled P that lies on a straight line with the two charges. The distance between any two items is all 5...
  13. H

    Question regarding charges on a hollow sphere

    Homework Statement I have a hollow conducting sphere with a charge on it, and I'm looking at the static situation. Where are the charges located? Homework Equations Gauss' Law The Attempt at a Solution A static situation, so no electric field inside the sphere, or charges would move...
  14. U

    I need a step by step for this problem dealing with charges.

    Homework Statement There are two balloons of charges +3.37mC and -8.21mC. The distance between the two balloons is 2.00m. Determine the force between the two balloons. Homework Equations The Attempt at a Solution Here’s my work: (9.0×10^9Nm^2/C^2)((3.37mC)(8.21mC)/(2.00m)^2)...
  15. S

    MATLAB Matlab, Three Dimensional plot of three charges

    What the program needs to do is quite simple, the problem is that I lack the knowledge needed to program in matlab. I know how to program in assembly and C++ and that's about it, this would not be a problem for me if my University gave formal courses in how to use Matlab. Here is what the...
  16. O

    What difference is between Beta particle and negative charges?

    "Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. " Negative charges also contain electrons, Beta particle are...
  17. O

    What charges on high voltage circuits?

    People usually use an electrostatic voltmeter for direct measurement. I would like to know what kind of charges is on following high voltage circuits. Will it be positive or negative charges? Does anyone have any suggestions? Thanks in advance for any suggestions
  18. F

    Are the charges of electrons necessarily integer values?

    It seems as if the charge we have labelled the electron with has simply been inferred by comparing it to the proton, in which case it is pretty much exactly the opposite, so we give the proton and electron charges of +1 and -1 respectively. This is fine, but when we get to the standard model...
  19. O

    Why losing charges under light?

    Does anyone have any suggestions on what charge of static electricity is being applied into the material? When this material is exposed to light the areas exposed lose the charge, Does anyone know what kind of process it is for losing the charge under light? Thanks in advance for any...
  20. W

    Force on charges inside/out of a hollow conductor

    Homework Statement Two charges, q and q', are located respectively, inside and outside a hollow conductor. Charge q' experiences a force due to q, but not vice versa. Prove this statement and explain the apparently violation of Newton's third law. There is no net charge on the conductor...
  21. P

    Choose the best answer on Magnetic Fields and Moving charges

    1)A wire is carrying a current, i, in the positive y-direction. The wire is located in a uniform magnetic field, B, oriented in such a way that the magnetic force on the wire is maximized. The magnetic force acting on the wire, FB, is in the negative x direction. What is the direction of the...
  22. P

    Particle Charges? - Pauline's First Post - Exploring Fractions of Charges

    Hello, I am Pauline!, this is my very first post, I am new to this, I've only been teaching my self this, so please don't be mean! my question is this: I've noticed some particles have a fraction of a charge for example, a up quark has a 2/3 charge and a down quark has -1/3 charge. how can there...
  23. N

    Would anything change electric charges could be complex numbers?

    Consider an Argand diagram that shows the number line (positive and negative) and the imaginary plane of other possibilities. As in, we have numbers that are positive and negative, and through complex numbers all of the polarities in between. I am using this as an analogy, because we have...
  24. L

    How Does Charge Interaction Affect Spring Dynamics?

    Homework Statement Charge Q1 is fixed to the ceiling by means of a spring with the spring constant D and is moved from its rest position (which is at y=h) by the two charges Q2. The gravitational force may be neglected. a) Determine the resulting force on Q1 in dependency of y. b) The...
  25. K

    Fraudulent card charges, but my card was not stolen?

    So I found out today my credit card account has about $200 worth of charges I did not make. However, my card has been in my pocket the whole time. How can this happen? If someone knew my SSN, how could they make charges without my card?
  26. W

    Potential of two point charges

    Homework Statement Two point charges q1 and q2 are located on a straight line normal to a grounded (V=0) conducting plane. Choosing the z axis to go through the charges, q1 is at a distance z1 above the conductor, and q2 is at a distance z2. Find the potential V(x,y,z) everywhere above...
  27. H

    Electric Field Between two Charges Equals 0

    Homework Statement A 3.17 μC and a -2.19 μC charge are placed 3.65 cm apart. At what point along the line joining them is the electric field zero? Assume that the first charge is at the origin and the second charge is at +3.65 cm. Homework Equations E = K(q) / r2 Ep = E1 + E2 0 = E1 + E2 -E1...
  28. D

    The electric field of infinite line charges and infinite sheet of charges

    Homework Statement Q1,Infinite uniform line charges of 5 nC/m lie along the x and y axes in free space. Find E at (a), P(0, 0 , 4); and (b), P (0 ,3 , 4) Q2, Three infinite uniform sheets of charge are located in free space as follows: 3 nC/m2 at z= -4, 6 nC/m2 at z=1, -8 nC/m2 at z=4...
  29. H

    How Does Gauss' Law Apply to Non-Symmetrical Shapes and Charge Distributions?

    Homework Statement Gauss' Law states: ∫∫ E.dS = ∫∫∫ div(E) dV = Qenc/ε₀ The proof is as follows (this is from Marsden's Vector Calculus 5e): Let M be a elementary region in ℝ3. Then if (0,0,0) ∉ ∂M, we have: ∫∫∂M r.n/r3 dS = 4π if (0,0,0) ∈ M = 0 if (0,0,0) ∉ M Construct a sphere of...
  30. L

    2 charges located in the x-y plane

    Homework Statement Consider 2 charges located in the x-y plane; q1 of magnitude 5 mC (millicoulombs) is located at the origin, and q2 of unknown magnitude is located at (x,y) = (0.1, 0) (in metres). The electric field E at position (0.03, 0.05) is found to be entirely in the +y direction...
  31. DocZaius

    Exploring Voltage Between Point Charges and Its Implications

    Today I was reflecting about the statement that increasing the distance between two large charged plates increases voltage, when I started to wonder what the behavior was near point charges (more voltage? as much? less?). Q and -Q are charges. P1 and P2 are locations. Q @ x=0m P1 @ x=1m...
  32. E

    Electric PE of a system of point charges

    My physics textbook defines the electric potential energy of a system to be equal to the external work that must be done to assemble the system, bringing each charge in from an infinite distance. And then it goes on the explain an example: "Figure 24-15 shows two point charges q1 and q2...
  33. K

    Find the charge of 2 point charges, given Uelec and total charge

    Homework Statement Consider two point charges a distance 1.5 cm apart. These charges have an electric potential energy of -190 micro J. The total charge of the system (the sum of the two charges) is 26 nC. What is the charge of each point charge? Homework Equations Uelec = K*q1*q2/d...
  34. S

    8-point charges on a vertice of a cube

    Homework Statement I attached a picture to make it easier... Homework Equations Coulomb's Law: F=k(q1*q2)/(r)^2 a^2+b^2=c^2 Charge properties The Attempt at a Solution I uploaded a picture of one of the cleaner sheets of work I used so far...Basically, I suppose I'm at a...
  35. S

    Does charges remain in an extension cord when unplugged?

    I am referring to this: A brainwave hit me and I wondered the following: If the moment when i unplug or switch it off (In my country they have a switch for added safety reason), the live wire happens to be at the peak of the AC curve, will my extension cord effectively become similar to a...
  36. C

    Finding Electric Field for Three Point Charges

    Homework Statement The questions are based off of the diagram I attached. First, I had to find the strength of the electric field due to each charge at (0 cm, 8 cm). Now I need to find the total electric field (both magnitude and direction) at (0 cm, 8 cm) and the total electric potential...
  37. M

    Potential energy of a system of three charges.

    Homework Statement A point charge q1 = 4.10 nC is placed at the origin, and a second point charge q2 = -2.95 nC is placed on the x-axis at x =+ 20.0 cm. A third point charge q3 = 2.00 nC is to be placed on the x-axis between q1 and q2. (Take as zero the potential energy of the three charges...
  38. J

    Archived Finding the electric field between two lines of charges using Gauss Law

    Homework Statement The problem is given in the attachment belowHomework Equations (i)EA= Q/epsilon naught (ii)Area of cylinder used = 2pi*r*L (iii)The integral of E*dA =Q/4pi*epsilon naught (iv) Llamda= Q/LThe Attempt at a Solution Well I know I needed to choose a suitable Gaussian surface...
  39. F

    Hanging pith ball problem with unequal masses and charges

    Homework Statement Suppose that two balls are suspended by identical threads of length .10m anchored to the same point. The pith balls have different masses and charges. The charge of one is 2.0 X 10^-7 C and the other one is 6.0 X 10^-8 C. Both threads make a 25 degree angle at...
  40. M

    Strength of hyrdrogen charges between ethanol and water

    Is a hydrogen on an ethanol more or less positive than on a water molecule. I think the hydrogen is more positive on a water molecule, but I still don't understand why? Could someone help me figure this out... please and thank you :wink:
  41. Telemachus

    Three equal charges are situated at the vertex of an equilateral

    Hi there. I did this problem, and I wanted to know if my solution is ok. The problem says: Three equal charges are situated at the vertex of an equilateral triangle, and we want to cancel out the forces exerted by each other. What charge q' of opposite sign should be placed at the center of the...
  42. P

    Electric Charges (max and min)

    A positive charge Q is on the y-axis at a distance a from the origin, and another positive charge q is on the x-axis at a distance b from the origin. A) For what values(s) of b is the x-component of the force on q a minimum? B) For what values(s) of b is the x-component of the force on q a...
  43. F

    Three Point Charges in a Row, Find Magnitude 1.5cm left of middle charge

    Homework Statement Consider three charges arranged as shown. + + - 1 2 3 What is the magnitude of the electric field strength at a point 1.5 cm to the left of the middle charge? The value of the Coulomb constant is 8.98755 × 10^9N  m2/C2. Answer in units of N/C q1=8.2 µC= 8.2*10^-6...
  44. T

    Calculating Electric Fields of 3 Charges on a Line

    Three charged objects are arranged on a vertical line as shown in the figure. The separation between charges is 3.0 cm. a) If you wanted to find the force on charge C, which fields would be relevant? Explain and calculate the magnitude of this field. Which direction does it point? b)...
  45. B

    Equilibrium of Four Point Charges in a Square: Calculating Charge Q

    Four identical point charges of q = 8.37 nC are at the four corners of a square with a side length of 11.2 cm as shown in the figure. (had to make it but same thing since I can't copy it) q q Q q q Edit: doesn't come out right when I post so imagen a square little q's on...
  46. F

    Point charges acting on a point

    Homework Statement Three point charges are located at the vertices of an equilateral triangle. The charge at the top vertex of the triangle is -4.4 µC. The two charges q at the bottom vertices of the triangle are equal. A fourth charge 2 µC is placed below the triangle on its symmetryaxis, and...
  47. A

    2 identical charges @ x=a & x=-awhere does E field vanish?

    Homework Statement Determine at what point or points (not including points at infinity) the electric field vanishes. Homework Equations The Attempt at a Solution Well, this seems to be a conceptual question and as I must be missing the concept, I don't know how to attempt to...
  48. A

    Magnitude/direction of point charges

    Homework Statement (a) Find the magnitude and direction of the net electrostatic force exerted on the point charge q3 in the figure below. Let q = +1.5 µC and d = 27 cm. http://www.webassign.net/walker/19-31.gif Homework Equations The Attempt at a Solution I found Fx = 1.7 N...
  49. N

    Point charges in an electromagnetic field

    point charges in an electric field Homework Statement Problem: A +8.75 micro C point charge is glued to a frictionless table. It is tied to -6.5 micro C point charge by a 2.5 cm string (weightless and nonconducting). A uniform electric field of magnitude 1.85*10^8 N/C is directed parallel to...
  50. jfy4

    Express electrostatic energy in terms of both charges

    Homework Statement For two concentric conducting spheres (radius a and b, b>a) that form a capacitor with charge q on the inner sphere and -q on the outer sphere, express the electrostatic energy in terms of q and -q and the potential difference between them.Homework Equations Gauss's Law, the...
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