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. A

    Calculating the force on an electron from two positive point charges

    So this is more of an intuitive question rather than a mathematical one. I present the problem. Assume I have 2 charges of charge +q at a distance r from each other on the z axis. Position of two charges is (0,0,r/2) and (0,0,-r/2). Assume now that I want to calculate the force these two...
  2. A

    Point charges placed inside a charged sphere

    I traced a spherical X-ray Gaussian (green) where the negative charges were diametrically opposite. My question is this: I can transform the entire charge of the Gaussian sphere into a point charge placed in the center. So, can I analyze only the electrical forces of the two negative charges...
  3. Z

    Potential Gradient for individual charges and parallel plates?

    In my book, the potential gradient for a charge placed anywhere in space is defined as: E = -V/r HOWEVER, for parallel plate (capacitors) the potential gradient is defined as E = V/d (V being the potential difference). How come there's no negative sign for the potential gradient of the parallel...
  4. H

    Where did I go Wrong? Solving for Particle Speed with Mass & Charge

    F= 9*10^9 (5*10^-9)^2 / (0.05)^2 a=F/m = F/(3*10^-6) v^2 = u^2 + 2aS = 0 + 2a*0.03 v = 60 Where did I do wrong? Thanks!
  5. A

    Charges, rod and magnetic field

    I have some difficulties in solving this problem. This is what I did. I wrote down the equation of motion for the masses. For the first point \begin{equation} m\ddot{\textbf{r}}_1=\textbf{F}_1=q\dot{\bar{\textbf{r}}}_1\times...
  6. F

    Software simulator for point charges & conductors

    Is there any software/simulator of point charges/conductors? Preferably with features enabling dynamics of charges.
  7. F

    Whether charges can stay inside wires or on the surface of a conductor

    There's an isolated capacitor initially carrying nonzero net charge. Then place the capacitor in a circuit connected with ideal wires (no resistance). Where will the excess charge go? Can they stay in wires or on any surfaces of conductors in the circuit? Electric field needs to be 0 everywhere...
  8. J

    Harmonic Motion Problem - Finding oscillation of charges in a circuit

    So since V(cap) + V(ind)=0 then Q/C + L dI/dt=0 Now since I=dQ/dt, I can replace dI/dt with d^2Q/dt^2 resulting in Q/C + L d^2Q/dt^2 =0 Now L d^2Q/dt^2 looks like a harmonic motion thing I can solve, where w^2=L. This means I can find w. I get 0.0005385. Now my issue is using this w gives the...
  9. S

    Calculating Forces on a Corner with Identical Charges

    Hi everybody, I tried to solve this problem but somehow I don't get it really. What I have to do. What I also know in this context is if its the same charge it will not attract otherwise if its the opposite charge it will attract. How do I have to calculate each charge on the corner? Question...
  10. badluckmath

    Electric Field of two line charges

    I'm trying to solve this, but i don't really know how to start this problem. There are two line charges and i must find the E. Field on the center.
  11. GeniVasc

    Work done via induced charges in a grounded conductor

    I'm currently studying Method of Images in Griffiths book and in section 3.2 he introduces the method of images for a point charge at a distance ##d## from a grounded conducting plane at potential ##V = 0##. In subsection 3.2.3, Griffiths compute the energy of the real system and the image...
  12. B

    Electromagnetism -- What do charges have to do to create EM waves?

    I am not sure, but I think the answer is between acceleration and velocity.
  13. J

    Fundamental Forces: Placing charges along a line so that the net force is zero at a point

    So 0=q1q3/r+q2q3/(13.6-r) 0=-8.5/r-3.63/13.6+3.63/r 0.2669=3.63/r-8.5/r r=-18.2465, but the answer is supposed to be 8.24
  14. S

    Two charges inside and outside a hollow conductor

    Please help
  15. Narayanan KR

    At least One Faraday Tube Between Every Two Unlike Charges in the Universe

    By Classic Coulomb's Law there exists negligible yet non zero force of attraction between two unlike charges in-spite of the distance. However for electrostatic attraction to work we need at-least one Faraday Tube(Lines of Forces) between the attracting charges, does that means...
  16. mcastillo356

    Two charges accelerated first by ##\Delta{V}##, then by ##\vec{B}##

    $$R_1=\dfrac{m_1 E}{|q|B}$$ $$R_2=\dfrac{m_2 E}{|q|B}$$ $$\therefore{\dfrac{R_1}{R_2}=\dfrac{m_1}{m_2}}$$ In my opinion, the answer to a this multiple choice question is c)
  17. greg_rack

    Charges of capacitors in series and in parallel

    Very simply, I can't understand why the charges of capacitors placed in series are all the same, and why even the total one(of the circuit) is equal to those. How is it possible that the total charge is the same as the individual ones? There must be some concept/property about capacitors which...
  18. M

    Three positive point charges are located on a line (Coulomb's Law)

    I need some help resolving the follow problem. I really don't know where to put the "twice as large as the resultant force on Q3" in order to build an equation. Thank you !
  19. E

    Velocity of charges or bounding curve features in motional EMF?

    The motional EMF is$$\mathcal{E}_{\text{motional}} = \oint_{\partial \Sigma} (\vec{v} \times \vec{B}) \cdot d\vec{x} = \int_{\Sigma} \frac{\partial \vec{B}}{\partial t} \cdot d\vec{S} - \frac{d}{dt} \int_{\Sigma} \vec{B} \cdot d\vec{S}$$(that's because Maxwell III integrates to...
  20. cwill53

    Zero Force from 3 charges placed at the vertices of a Triangle

    I'm not really sure where to start with this problem, but I wanted to ask a few questions about the approach I should use. Is it reasonable to say that a gradient could be set up that could describe the force on the fourth ion at any point? The way I'm thinking of this problem is, I want to...
  21. LCSphysicist

    Three charges attached to the vertices of a triangle

    Actually we find the two position in the axis very easily, but, what am trying to find is if exist such position (Being the charge of the ions equal) away from the symmetry axis, but i really don't want to try find it numerically, it would be a disaster. The only conclusion i got is, if such...
  22. archaic

    Cube with charges at each vertex

    For convenience, I take the center of the upper face. The charges at the top cancel each other's effects, and those at the bottom cancel each other's horizontal effects, so I get$$E=4k\frac{q}{r^2}\sin\theta$$I have found that ##\theta=\arcsin\left(\frac{s}{r}\right)=\arcsin{\sqrt\frac{2}{3}}##...
  23. Amitkumarr

    To find induced charges on the edges of a right pyramid

    Due to symmetry of the system,when the frame is rotated to make the electric field point from corner A to corner C,the magnitude of charges induced on these-(AB,BC,CD,DA),(OA,OC),(OB,OD) will be equal(different for each group but same for elements in these groups). For the sign of induced...
  24. J

    Point-like charge between grounded plates: Induced charges

    I don't understand why moving charge doesn't affect the magnitude of induced charge. Could someone explain why it is possible? Thanks in advance.
  25. C

    Frequency of EM waves produced by linearly accelerating charges

    I was wondering about EM waves produced by linearly accelerating charges, as opposed to oscillating charges. With oscillating charges, the frequency of the wave depends on the frequency of the oscillation of the charge. But what determines the frequency of the wave produced by a linearly...
  26. F

    Induced/bound charges in conductors and dielectrics

    When placed in an electric field, a conductor has induced charges and a dielectric has bound charges. When there's no net bound charge density in the bulk of the dielectric, bound charges stay on the surface only, like induced charges in conductors. In Maxwell's eqs, the induced charges are...
  27. T

    Understanding Balloon Charges and Interactions

    Balloon A is + as negatively charged rod attracts it Balloon B is - as Balloon A attracts it. Since Balloon A (+) repels balloon C so it means Balloon C is +. Balloon D attracts Balloon Balloon B (-) so it means Balloon D is +. Balloon E is neutral as negatively charged objects and neutral...
  28. F

    What happens to surface charges when conductors/dielectrics touch?

    When 2 conductors/dielectrics touch, will surface charges move away from their original conductor/dielectric to the other?
  29. gumthakka

    Current and stationary charges

    I've learned that moving charges produce magnetic fields which in turn affect other charges in motion. After seeing explanations that point to special relativity, I am kind of confused. Can **ALL** magnetic fields be accounted as some kind of electric field from a particular reference frame...
  30. F

    The real reason for a capacitor having the same amounts of + and - charges on the two plates

    Most textbooks say that a capacitor whether it be a single one or one in series/parallel should have equal amounts of + and – charges on both plates and that they mostly conclude the + charges attract the same amount of – charges on the other plate without giving any reason. Now I claim that...
  31. N

    Calculating Electric Field for 4 Point Charges in a Square Configuration

    I have the following question and I can't figure out how to, is there anybody who can help?
  32. A

    Potential energy of a system of two punctual charges along the X axis

    I have not clear how to solve this problem. Here it is my attempt at a solution: Let the charge at ##-a## be the number one and the one at ##+a## the number two. the potential energy of the punctual charge ##-Q## due to each charge +Q will be then ##E_{pi}=-k \frac{Q^2}{r_i}##, whit ##r_i## the...
  33. r-swald

    Find the escape velocity from 2 point charges

    Below is the work I've attempted. I used 2 PE b'c there were 2 point charges, and only one KE b'c only the proton is moving. The final equation in case it's hard to see is V(esc) = sqrt (4kQq / mr). I'm not sure if I did it right. Did I set up this equation right? and I am also not sure what...
  34. P

    Potential energy of a System of charges

    This is my attempt the system The 1 is the initial configuration where the 3 electron is at infinity. The 2 is the final configuration where the 3 electron is midway.U1 is the potential energy between e1 and e2 U1 = (q1*q2)/(4*π*ε0 * (0.02)^2); // q1, q2 charge of electrons K1 =...
  35. G

    E-field at the origin from two point charges

    Using superposition and "breaking up" the vectors into three components ax, ay, az on points should solve the task. For Q1 there is no effect on x-axis. On the y-axis the distance from Q1 to origin is 2. Using coulombs law will give us -> (-Q/4) * k , where k is the constant 1/(4*pi*e0). On...
  36. Zohar

    Oxidation States of Molecules and Atoms and the Relationship with Charges

    Hey, y'all. I know the oxidation state of a carbon in an ethene is -2 while carbon in Acetylene is -1. As well I know acetylene has more disspating elcetrons due to pai bonds. So how come charges between the acetylene carbon are more negative than in ethene while the carbones oxidations states...
  37. T

    Electric field within the cavity of a hollow conductor polarized by external charges?

    Suppose we have a hollow metallic conductor, just a thin metallic shell forming a large hollow cavity. It is then polarized by electric charges placed nearby externally. The equilibrium electric field must be parallel to the surface normals of the shell, there must be no tangential component...
  38. G

    Engineering Calculating the total electric field from two charges

    a) Should be pretty straight forward, from the equation E = kQ/R , we see that scaling is simply 1/R. b) Here is gets a bit trickier. We know that q acts as a source (E-field points outwards) and -q acts as a sink (E-field points inwards). If the distance is far away do we consider the Q1 and...
  39. vis viva

    What happens to cations and electrons during and after a gas discharge event?

    As I understand both cations and electrons are produced between cathode and anode in a gas discharge, but what is their imminent fate, during and post discharge event? The majority of information I could find only covers the electrons from the time of the first ionization event to impacting the...
  40. A

    5 charges placed at 5 vertices of a regular hexagon

    If 5 charges (each q) are placed at 5 vertex of a regular hexagon of side a then effectively the electric field at the centre of the hexagon is $$\frac{q}{4\pi\epsilon_0a^2} $$ but the potential is $$\frac{5q}{4\pi\epsilon_0a}$$ but then what about $$V=-\int \textbf{E•dr}$$
  41. S

    Three Charges inside a Metal Sphere

    I know that for a conductor the charge is uniformly distributed and the electric field is zero inside the shell. However, I am not sure how to calculate the charge inside the shell so I can know the electric field.
  42. T

    In electrostatics, what is meant by positive charges?

    I am needing clarification for a concept. I understand that electrons carry a negative charge and that protons carry a positive charge. I also understand that a plastic rod picks up electrons when I rub it with a piece of wool. From the conservation of charge, the piece of wool must have a...
  43. S

    Location where the electric potential is zero between charges

    a) I take "a point where it is neutral" as the electric potential at that point is zero. Is this correct? And because the two charges are both negative, there can not be any point where V = 0? Am I wrong or maybe one of the charge should be positive? Thanks
  44. A

    Resources on non-spherical conductor surface charges

    Hi all, I know qualitatively that charges tend to concentrate on sharp edges of conducting surfaces. I have tried searching online for a mathematical treatment of such a phenomenon, but I cannot find anything that's quite rigorous. I'd appreciate it if someone could guide me towards such...
  45. moeug1999

    How do I find the other charge using electric potential?

    I tried looking for the other charge using the equation k|q1||q2|/r^2 but it tells me that my answer is wrong
  46. moeug1999

    Electric Potential at A and B: Find the Answer

    I found the potential at A, however I tried doing it with B but it says I have the wrong answer.
  47. moeug1999

    Help! I'm Stuck on an Equation My Professor Gave Me

    My professor does not walk us through the problem. He literally just gave us an equation and that's it. I do not know how to do this problem.
  48. moeug1999

    Coulomb's Law: Solving Problems with Electric Charges

    This is my attempt but they said my answer is wrong
  49. D

    Electric field involving 4 point charges in a rectangle

    I am stuck on the following question (Image attached of my work) appears to make sense until i try to take a limit as c--->0 because the result should be 0. Am i missing something, if so can't you point me in the right direction. Thank you
  50. E

    Is thinking about "possession" of electrons a bad habit for dealing with formal charges?

    This isn't a specific question, but more a case of trying to mitigate any potential confusion which might arise in the future. When drawing out curly arrows for mechanisms, and the like, I'm used to thinking about which electrons "belong" to certain atoms (in a book-keeping sense) in order to...
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