What is Conservation of charge: Definition and 31 Discussions

In physics, charge conservation is the principle that the total electric charge in an isolated system never changes. The net quantity of electric charge, the amount of positive charge minus the amount of negative charge in the universe, is always conserved. Charge conservation, considered as a physical conservation law, implies that the change in the amount of electric charge in any volume of space is exactly equal to the amount of charge flowing into the volume minus the amount of charge flowing out of the volume. In essence, charge conservation is an accounting relationship between the amount of charge in a region and the flow of charge into and out of that region, given by a continuity equation between charge density




{\displaystyle \rho (\mathbf {x} )}
and current density





{\displaystyle \mathbf {J} (\mathbf {x} )}
This does not mean that individual positive and negative charges cannot be created or destroyed. Electric charge is carried by subatomic particles such as electrons and protons. Charged particles can be created and destroyed in elementary particle reactions. In particle physics, charge conservation means that in reactions that create charged particles, equal numbers of positive and negative particles are always created, keeping the net amount of charge unchanged. Similarly, when particles are destroyed, equal numbers of positive and negative charges are destroyed. This property is supported without exception by all empirical observations so far.Although conservation of charge requires that the total quantity of charge in the universe is constant, it leaves open the question of what that quantity is. Most evidence indicates that the net charge in the universe is zero; that is, there are equal quantities of positive and negative charge.

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  1. Pushoam

    I Conservation of charge in the Universe

    The charge of an isolated system is conserved. This implies the charge of the universe is constant. This implies that charge can neither be created nor destroyed. This implies that the net positive charge and the net negative charge of the universe are conserved. Is this right?
  2. F

    Conservation of charge with Dirac delta

    Hello, I was reviewing a part related to electromagnetism in which the charge and current densities are defined by the Dirac delta: ##\rho(\underline{x}, t)=\sum_n e_n \delta^3(\underline{x} - \underline{x}_n(t))## ##\underline{J}(\underline{x}, t)=\sum_n e_n \delta^3(\underline{x} -...
  3. L

    How does this capacitor circuit not violate conservation of charge?

    There must be something I'm not understanding about capacitors in series. I know that we can treat them as one equivalent capacitor with: (1) with 1/Ceq, (2) same Q as anyone of the capacitors, (3) and add up the Vs for the sum total V across them. If the equivalent capacitor (Ceq) would...
  4. Keanthon

    Charging a low voltage battery with a higher one of same Ah

    Let's say both battery have the same charge capacity of 3Ah Battery A has voltage of 3V and B has voltage of 6V. Battery A is completely discharged while B is completely charged. If I charge battery A with battery B, wouldn't B be completely drained because they hold the same amount of charge...
  5. K

    Conservation of energy of a perfectly decoherent laser

    The energy and momentum of a closed system is always conserved. If a laser can emit perfectly parallel and perfectly superimposed light waves (occupy the exact same space) that are perfectly 180° out of phase and of the same frequency, what can be said about the energy and momentum of the...
  6. I

    Connecting three spheres with wires redistributes charge

    Homework Statement There are three identical conducting spheres, A, B and C. They are initially charged as q_A = 0, q_B = 0, q_C = +Q. Initially, A and B are connected by a wire. Then the spheres are connected (by a wire) as follows: 1) A to C (while A is still connected to B) 2) Connection...
  7. davidge

    I QM Phase Symmetry & Charge Conservation

    What equation in QM show us that symmetry in quantum-mechanical phase implies charge conservation?
  8. MullaTheMech

    Conservation of charge vs force

    So I was posting questions in someones homework help and I thought I'd create my own thread instead. https://www.physicsforums.com/index.php?threads/868492/ Now in coulombs equation you multiply the coulombs (Q1×Q2) Ujjwal (OP in other thread) was using 2 balls charged at 2 and 3 coulombs in...
  9. Bigger than smaller

    Conservation of Charge in Series Capacitors.

    Hi. I have a question about conservation of charge when two differently charged capacitors are connected in series. I know this is like a homework problem of introductory level of physics, but since this is not my homework, I decided to post it here. So, here is the story. There are two...
  10. M

    Conservation of charge and LHC

    I don't know much about the topic but if I'm correct charge should always be conserved. What happens when two protons collide in the LHC? Don't they split into quarks and then decay, lowering the amount of positive charge in the system?
  11. D

    Local Conservation Of Charge And Quantum Mechanics

    I understand it from a classical viewpoint, like the flow of a fluid. But shouldn't an electron obey the rules of QM? How is teleporting from one place to another forbidden in QM, wat about tunneling.Where is your continuous flow now? What about Quantum Entanglement. I don't get it.This...
  12. L

    Charge Conservation & Mass-Energy Equivalence

    What will happen to charge on electron if eletron's mass is converted to energy according to Mass-Energy equivalence principle. Would the charge on electron be conserved? If yes, then were would it go as there is no mass now.
  13. M

    Can Electric Fields be Discontinuous? - Conservation of Charge

    I show the conservation of charge from the equations of MAxwell, but I suppose that an electric field is continuous at space and time, therefore I can exchange the derivates from Gauss' law, at time's derivate of this law.. My question is, At nature Can I have an electric field discontinued...
  14. S

    Simple Capacitor and Conservation of Charge Question.

    Homework Statement Capacitors C1 = 6.18 µF and C2 = 1.69 µF are charged as a parallel combination across a 250 V battery. The capacitors are disconnected from the battery and from each other. They are then connected positive plate to negative plate and negative plate to positive plate...
  15. A

    Does the weak force violate conservation of charge?

    Dear Physics Forum, I am a little confused about conservation of charge vs. charge conjugation. I'm reading David Griffith's book "Intro. to Elementary Particles"... pg. 81 "All three interactions (weak, strong, EM), of course, conserve electric charge. In the case of weak interactions...
  16. V

    Capacitors - Conservation of Charge vs Conservation of Energy

    I am a TA for a physics teacher. I wrote a problem that the students did in the lab quiz. The students tried to use conservation of energy instead of conservation of charge, which I used. Both methods seem sound to me, but they produce different answers. I need help figuring out which method is...
  17. T

    Nuclear equations and conservation of charge

    Do you know why in most textbooks, like on http://www.lbl.gov/abc/Basic.html or http://books.google.com/books?id=xD0AwBQECasC&pg=PA196 beta decay equations are written like ^{14}_{6}C\rightarrow^{14}_{7}N+e^{-}+\overline{\nu}_{e} instead of...
  18. A

    How does conservation of charge work?

    Example: A conducting sphere X that has an initial charge of +2.0 × 10–8 C and an identical conducting sphere Y that has an initial charge of –3.0 × 10–8 C are touched together. After they are separated, the charge on sphere X is? Answer: (–5.0 × 10–9 C) And what I would have done is tried to...
  19. mrspeedybob

    Black holes and conservation of charge

    Suppose you take a quantity of matter and separate the protons from the electrons, Now drop the electrons into a black hole. My understanding is that photons are the force carriers for the electromagnetic field. Since no photons can escape the black hole there should be no electrostatic...
  20. H

    Conservation of charge and electron flow?

    I am trying to understand the conservation of charge regarding electron flow through a charged body. Is there any thing about the conservation of charge which explains that if a body is charged and electrons leave the body the same amount of electrons must enter it to conserve it's charge...
  21. P

    Law conservation of charge relativistic

    \frac{\partial \rho}{\partial t}+div\vec{j}=0 In Deckart coordinate system \frac{\partial j_x}{\partial x}+\frac{\partial j_y}{\partial _y}+\frac{\partial j_z}{\partial _z}+\frac{\partial (c\rho)}{\partial (ct)}=0 definition divA^{\mu}=\frac{\partial A^{\mu}}{\partial x^{\mu}} scalar...
  22. S

    Conservation of charge problem

    Homework Statement Which of the following reactions could not occur because they would violate conservation of charge (n=neutron, p=proton, e- = electron, he^2+ = the helium nucleus) a) p -> n + e- b) n -> p + e- c) He^2+ + He^2+ -> He^2+ p + n d) p + He^2+ -> He^2+ + e- e) p + p +...
  23. I

    Conservation of charge, but not conservation of energy

    Homework Statement A DC voltage (V) in series with a resistor of value R and in series with a capacitor (C1) at time t=0 a switch closes to put another capacitor (C2) in parallel with C1 and in series with V and R. The charge on C1 at t=0- Q1(0-)=/0 (doesn't equal 0) and charge on C2 at t=0-...
  24. S

    How Does Charge Redistribution Affect Forces in a Triangular Sphere System?

    Homework Statement In the figure 21-40, three identical conducting spheres form an equilateral triangle of side length d = 24.0 cm. The sphere radii are much smaller than d and the sphere charges are qA = -3.45 nC, qB = -3.91 nC, and qC = +6.09 nC. (a) What is the magnitude of the...
  25. S

    Baryon asymmetry and conservation of charge

    I am confused with baryon asymmetry and conservation of charge..we say that there is baryon asymmetry but the universe is neutral..how is that possible..if there is baryon asymmetry then there should be charge asymmetry also? I think i am missing some point..can someone explain these two in...
  26. E

    Charge Conservation: A+2 & B+7 → A+5 & B+5

    Now suppose we have two conductors A and B. A has a charge of +2 and B has a charge of +8. If we let the two conductors touch and then separate them, each will have a charge of +5. This is because charge is conserved and will flow between the two conductors until each have equal charges. Ok...
  27. M

    Symmetry and Conservation of Charge

    I understand that all conservation laws have underlying symmetries and that all symmetries have corresponding conservation laws. From reading some popular science books (don't shoot me :P), I understand that conservation of energy, linear and angular momentum are a natural consequence of time...
  28. H

    Conservation of Charge: Explaining the Point Rule

    Why does the point rule arise as a consequence of conservation of charge?
  29. R

    Evaluating the rate of increase of charge at x=2 yields a value of 16.

    The law of conservation of charge states that the net current due to flow of charge emanating from a closed surface S is equal to the time rate of decrease of the charge within the volume V bounded by S \oint_{s}J\cdot\,dS=-\frac{d}{dt}\oint_{V}\rho\*d\upsilon Can the time rate of...
  30. S

    Modeling conservation of charge

    A group of physics students designed the following experiment to test the model of conservation of charge. a) They first charged a capacitor C1 = 5600 micro F by applying a voltage V_0 = 10 volts (as shown in attachment Exam 2 - Problem 2 - Part a.JPG) b) Then the connected a second...
  31. S

    Modeling conservation of charge

    A group of physics students designed the following experiment to test the model of conservation of charge. a) They first charged a capacitor C1 = 5600 \mu\f